WO2000017906A2

WO2000017906A2 - Rf plasma etch reactor with internal inductive coil antenna and electrically conductive chamber walls

Info

Publication number: WO2000017906A2
Application number: PCT/US1999/021740
Authority: WO
Inventors: Yan Ye; Donald Olgado; Ananda H. Kumar; Yeuk-Fai Mok; Allen D'ambra; Avi Tepman; Diana Ma; Gerald Yin; Peter Loewenhardt; Jeng Hwang; Steve Mak
Original assignee: Applied Materials, Inc.
Priority date: 1998-09-22
Filing date: 1999-09-21
Publication date: 2000-03-30
Also published as: EP1147544A2; WO2000017906A3; JP2002525866A; TW434638B

Abstract

The present invention provides an inductive antenna secured within a processing chamber. The antenna may be constructed so that it can be attached to an electrically conductive chamber wall and so that it readily transfers heat to the chamber wall. Conductive chamber walls provide an improved anode for the bias circuit and allow for temperature regulation of the antenna. In one possible embodiment, the antenna may comprise a conductor surrounded by an electrically insulative, thermally conductive, non-sputtering material, such as ceramic, which may be attached to the chamber wall. To reduce inductive power attenuation, the exposed surface of the antenna may be separated by gaps which inhibit eddy currents from flowing in conductive deposits on the antenna. Adjacent antenna turns, as well as the turns themselves, may be separate by gaps. The dimensions and shape of the gap inhibit conductive etch byproduct from bridging the gaps. Dummy rings may be located between antenna rings and removed to facilitate cleaning. Process gases may be fed to the chamber via the gaps.

Description

RF PLASMA ETCH REACTOR WITH INTERNAL INDUCTIVE COIL ANTENNA AND ELECTRICALLY CONDUCTIVE CHAMBER WALLS

BYYan Ye, Donald Olgado, Anada H. Kumar,

Yeuk-Fai E. Mok, Allan D'Ambra,

Avi Tepman, Diana Ma, Gerald Yin,

Peter Loewenhardt, Jeng Haung, and Steve Mak

CROSS REFERENCE This is a continuation-in-part of U.S. Patent Application serial no. 08/869,798, filed June 5, 1997, issued as U.S.

Patent Number on , by Ye, et al., entitled RF

PLASMA ETCH REACTOR WITH INTERNAL INDUCTIVE COIL ANTENNA AND ELECTRICALLY CONDUCTIVE CHAMBER WALLS, herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

Technical Field

The invention relates to an inductively coupled plasma reactor .

Background Art

Conventional inductively coupled plasma reactors typically have an inductive antenna and a capacitive bias. The inductive antenna is used to generate the plasma and control its density while the capacitive bias is used to control ion energy at a workpiece. In conventional inductively coupled plasma reactors, the inductive antenna is located above the ceiling of the chamber. To facilitate the transfer of power from the inductive antenna to the plasma, the ceiling and upper portion of the side wall of the reactor chamber typically are made of a non- conductive material, such as quartz.

The bias power is applied to the workpiece via a pedestal which supports a workpiece. Typically, the lower portion of the reactor walls are made of an electrically conductive material and are grounded to form the anode of the bias circuit. As etching is ion driven, the characteristics of the bias circuit, which controls ion energy at the workpiece, are particularly important.

The conventional inductively coupled etch reactor has in the past been used to etch aluminum from the surface of a workpiece. This etching process produces byproducts comprising mostly aluminum chlorides (AlClx) and fragments of photoresist, which tend to deposit on the walls of the reactor chamber. The byproducts of an aluminum etch have no significant effect on etch rates because they are almost totally non-conductive.

Such is not the case when electrically conductive etch byproducts are produced and deposited on the chamber surfaces. For example, etching of copper (Cu) , platinum (Pt) , tantalum (Ta) , rhodium (Rh) , and titanium (Ti) , among others may create electrically conductive etch byproducts. Etching these metals presents a problem when using the conventional inductively coupled reactor.

Conductive etch byproduct on the walls and ceiling of the reactor has been observed, by the present inventors, to reduce the etch rate over time. A coating formed by the conductive etch byproduct on the walls and ceiling of the chamber has the effect of attenuating the inductive power coupled to the plasma. When the interior surface of the chamber under the antenna is coated with a conductive material, eddy currents are produced in ^""the material, thereby attenuating the power coupled to the plasma.

As the conductive coating builds in thickness over successive etch processes, the attenuation progressively increases and the power coupling into the plasma progressively decreases. It has been found that a 10 to 20 percent decrease in power coupled into the plasma occurs after processing 100 workpieces.

In addition, the conductive coating on the insulated portion of the chamber walls can electrically couple to the grounded anode portion of the chamber, thereby effectively increasing the anode area. This increase in anode area results in an unexpected change in the bias power.

The reduction of inductively coupled power and the increase in capacitive bias power have detrimental effects on the etching process. For example, the plasma ion density is lowered due to the decrease in inductively coupled power and the plasma ion energy is increased due to the increase in capacitive bias power.

As the power levels are typically set prior to the etching process to optimize plasma ion density and energy, any change could have an undesirable impact on etch quality. The changes in power coupling caused by conductive etch by-products coating the chamber also affect other etch process parameters and plasma characteristics, as well. For instance, the photoresist selectivity is lowered, etch stop depths are reduced, and ion current/energy distribution ana the etch rate are adversely affected. These changed parameters and characteristics result in different, and often unacceptable workpiece etch characteristics (such as poor photoresist selectivity, poor etch rate uniformity or etch rate shift, and device damage) . It has been found that even after only two or three workpieces have-been etched, unwanted changes in the etch profile can be observed. Furthermore, in addition to the detrimental effects on the etch process parameters and plasma characteristics, it has also been found that the reduced inductive coupling of power into the chamber causes problems with igniting and maintaining a plasma. Of course, the decrease in inductively coupled power could be compensated for by increasing the inductive power supplied to the inductive antenna. Similarly, the increase in capacitively bias power can be compensated for by decreasing the power supplied to the pedestal. Or, the chamber walls could be cleaned more often than would typically be necessary when etching materials producing non-conductive by-products.

These types of work-arounds, however, are generally impractical. A user of an etch reactor typically prefers to set the respective power levels in accordance with a so-called "recipe" supplied by the reactor's manufacturer. Having to deviate from the recipe to compensate for the conductive deposits would be unacceptable to most users. Furthermore, it is believed that the aforementioned detrimental effects will be unpredictable, and therefore, the required changes in the power settings could not be predetermined. Thus, unless the user employs some form of monitoring scneme, the required compensating changes in power inputs would be all but impossible for a user to implement. Realistically, the only viable solution would be to clean the chamber frequently, perhaps as often as after the completion of each etch operation. An increase in the frequency of cleaning, however, would be unacceptable to most users as it would lower throughput rates and increase costs significantly.

Another problem with conventional inductively coupled reactors is that the ratio of the surface area of the anode portion of the wall to the pedestal is too small. Since a large portion of the wall must be electrically non-conductive to facilitate inductive power transfer to the plasma, only a small portion of the wall is electrically conductive and may act as the anode for the capacitive bias supplied by an RF power source. It is desirable to have the surface area of the pedestal significantly less than that of the grounded portion so that the average voltage (often referred to as the DC bias voltage) at the surface of the workpiece is negative. This average negative voltage is employed to draw the positively charged ions from the plasma to the workpiece. If, however, the surface area of the pedestal is only slightly smaller than the surface area of the grounded portion, as is typically the case in a conventional inductively coupled plasma etch reactor, the average negative voltage at the surface of the workpiece is relatively small. This small average bias voltage results in a weak attracting force which provides a relatively low average ion energy. A higher negative bias voltage value than can typically be obtained using a conventional inductively coupled plasma etch reactor is necessary to optimize the plasma ion energy so as to ensure maximum etch rate while not creating significant damage to the workpiece. Ideally, the surface area of the grounded portion of the wall would be sufficiently large in comparison with that of the pedestal so as to produce the maximum possible negative average voltage at he surface of the workpiece, i.e. one half the peak to peak voltage.

Yet another drawback associated with the conventional inductively coupled etch reactor involves the cooling of J:he walls of the chamber. Etching processes are typically only stable and efficient if the chamber temperature is maintained within a narrow range. Since the formation of the plasma generates heat which can raise the chamber temperature above the required narrow range, it is desirable to remove heat from the chamber in order to maintain an optimum temperature within the chamber. This is typically done by flowing coolant fluid through cooling channels formed within the conductive portion of the chamber wall. As it is not easy to form cooling channels within the insulative portion of the chamber walls, air is directed over the exterior of these walls. A problem arises in that the electrically insulative materials, such as quartz or ceramic, typically used to form the chamber walls also exhibit a low thermal conductivity. Thus, the chamber walls are not ideal for transferring heat from the chamber. As a result, the chamber temperature tends to fluctuate more than is desired in the region adjacent the insulative chamber walls because the heat transfer from the chamber is sluggish. Often the temperature fluctuations exceed the aforementioned narrow range required for efficient etch processing.

These excessive temperature fluctuations can cause another problem. As discussed previously, etch by-products will tend to deposit on the chamber walls during the etch process. In attempting to control the chamber temperature by air cooling the insulative chamber walls, the chamber wall temperature and the layer of etch by-product formed on the interior surface thereof, tends to cycle. This cycling causes thermal stresses within the layer of etch by-product material which result in cracks and pieces of the material flaking off the wall and falling into the chamber. The loose deposit material can contaminate the workpiece, or it can settle at the bottom of the chamber thereby requiring frequent chamber cleaning.

SUMMARY

The plasma reactor of the present invention provides an inductive antenna secured within an plasma etch chamber. The antenna may be constructed so that it can be attached to an electrically conductive chamber wall. An advantage of placing the antenna within the etch chamber is that it allows the size of the electrically conductive portion of the chamber walls, which acts as an anode for the DC bias circuit, to be increased. Providing a larger anode allows etch rates to be optimized while not creating significant damage to the workpiece.

With the present invention, the antenna may be constucted and secured within the chamber so that it readily transfers heat to the chamber wall. The temperature of the antenna, therefore, may be regulated by regulating the temperature of the chamber wall. Among other advantages, this helps limit thermal expansion cycles and inhibits flaking or cracking of etch byproducts on the antenna and of the antenna itself. It also helps prevent separation of the antenna-to-wall coupling.

In a preferred embodiment of the present invention, the inductive antenna comprises a conductor surrounded by an electrically insulative jacket. The antenna, therefore, may be directly coupled to an electrically conductive chamber wall. With this embodiment, the antenna may be formed having a metal conductor completely surrounded by a ceramic block-shaped jacket which is also a good thermal conductor. The blocks may then be attached to the chamber wall, for example, by braizing so as to provide a good thermal connection.

The plasma reactor of the present invention may have the internal antenna formed so that it reduces the attenuation of inductive power caused by eddy currents in conductive etch byproduct build-up on the antenna surface. In one embodiment, the exposed surface of the internal antenna is separated by gaps which inhibit eddy currents from flowing in conductive etch byproducts on the surface of the jacket. In the case of a coil shaped antenna, it is preferred to separate adjacent antenna turns or ring segments from each other and to segment each turn into arcuate segments. In this embodiment, the gaps separate the surface of the segments of the antenna to inhibit conductive etch byproducts from electrically joining the turns or the arcuate segments. The dimensions and shape of the gap, therefore, are selected so as to inhibit conductive etch byproduct from electrically connecting the turns or the arcuate segments.

The gaps may be formed with parallel side walls having sufficient height to inhibit conductive etch byproduct from bridging the gap or connecting to the wall of the chamber. Furthermore, the gap must be narrow enough to inhibit plasma from forming in the gap. Typically, the gap is about .025 to 1 millimeter with the ratio of height to width being greater than about 5. As an alternative, or in addition to, the shape of the sidewalls forming the gap may be tailored to inhibit conductive byproduct from joining antenna segments. In one embodiment, the sidewalls step apart near the chamber wall so that the gap forms a "T" shape. The gaps may only separate the exposed surface of the antenna or may completely separate antenna segments.

The antenna may be unitary or segmented and can take on any configuration (e.g. location, shape, orientation) to optimize power deposition within the chamber. The location of the antenna within the chamber, the aspect of the jacket, and the location of the conductor within the jacket can be varied to control the deposition of power by the antenna within chamber.

The present invention may provide removable dummy rings between the antenna rings. Gaps between the dummy rings and the antenna rings may be provided as discussed above. The dummy rings can be removed during the cleaning process so that any etch by-product which accumulates in the gap is easily removed.

Another advantage of the present invention is that it allows the process gas to be delivered close to the antenna. In conventional inductively coupled plasma etch reactors, the inductive coil antenna precluded the incorporation of gas inlets on the portion of the chamber walls adjacent to the externally wrapped coil. This is troublesome because it is often desirable to inject etchant gas into regions of high power deposition, such as those formed immediately adjacent the coil antenna. Since the inductive antenna is disposed within the chamber of a reactor according to the present invention, this limitation in the placement of etchant gas inlets no longer exist. Thus, the inlets can be placed practically anywhere on the interior of the chamber walls, particularly in locations directly adjacent regions of high power deposition. If desired, the process gas may be delivered through gas ports located between the antenna turns. The size of the gap between the antenna turns, or between the antenna turns and dummy rings, must be selected so that plasma is not generated between the turns and so that conductive etch by-product does not block the ports.

In another embodiment of the present invention, the antenna could be made completely of a conductive ceramic such as boron carbide, or it could be constructed so as to have a metal core

(e.g. aluminum) with an outer jacket formed of a conductive ceramic material. In addition, the antenna could have a tubular structure with a hollow interior channel. This channel would be used to sustain a flow of coolant fluid therethrough for cooling the antenna and keeping it within a prescribed temperature range.

With these embodiments, the antenna must be coupled to the chamber wall so that it is insulated from ground. This may be accomplished by interposing a partial insulative jacket or layer between the chamber wall and the antenna.

The walls can be made with a protective layer forming the portion of the walls facing the interior of the chamber. The protective layer prevents sputtering of material from the chamber walls by a plasma formed within the chamber. Absent this protective layer, sputtered material from the walls could degrade the etching process quality and contaminate the workpiece undergoing etch, thereby damaging the devices being formed thereon. Preferably, the electrically conductive chamber walls are made of aluminum and the protective layer is aluminum oxide (i.e. anodized aluminum). The protective layer, however, could also be a conductive ceramic material, such as boron carbide.

In addition, since the chamber walls may be made conductive, any conductive by-products from etching processes performed in the reactor which deposit on the chamber walls will not have a detrimental effect on the plasma characteristics. For example, there would be no sudden increase in the capacitive coupling of RF power and ion energy caused by an electric coupling of the deposits to the grounded areas of the reactor which act as an anode for the energized workpiece pedestal. Thus, the use of electrically grounded conductive chamber walls in combination with an internal inductive coil antenna ensures, that the plasma characteristic do not change even when the etch process results in conductive by-products coating the interior walls of the chamber.

Chamber walls made of a conductive metals such as aluminum would also exhibit significantly greater thermal conductivity than that of conventionally employed electrically insulative materials such as quartz or ceramic. This results in a quicker transfer of heat from the antenna and the interior of the chamber to coolant fluid flowing through cooling channels formed in the chamber walls. Therefore, it is easier to maintain a narrow chamber temperature range and avoid the problems of a conventional etch reactor in connection with the cracking and flaking off of deposits from the chamber walls. Additionally, it is easier and less expensive to form cooling channels in aluminum chamber walls than in the conventional quartz walls. The present invention also allows for individual selection of the power levels of the RF power signals supplied to the coil segments (when used) to further tailor the power deposition pattern within the etch chamber. For example, an RF power signal exhibiting a higher power level supplied to a particular coil segment would produce a region of higher power deposition adjacent that coil in comparison to regions adjacent other similarly configured segments supplied with an RF signal having a lower power level.

In addition to the above-described advantages of a plasma etch reactor constructed in accordance with the present invention, it is pointed out that the amount of RF power inductively and capacitively coupled into the chamber can be varied by simply adjusting the amount of RF power supplied to the inductive coil antenna (or segments) and the energized pedestal. For example, a capacitively coupled plasma can be formed by providing RF power solely to the pedestal (and/or the conductive chamber walls) . Conversely, a purely inductively coupled plasma can be formed by providing RF power solely to the inductive coil antenna, or if applicable, to one or more of the independently powered coil segments. Or, the reactor can be operated using any desired mix of inductively and capacitively coupled RF power. Thus, the reactor can operated in an inductively coupled mode, capacitively coupled mode, or a combined mode. This provides the opportunity to use the reactor to perform a variety of etch operations over a wide process window.

In addition to the just described benefits, other objectives and advantages of the present invention will become apparent from the detailed description which follows hereinafter when taken in conjunction with the drawing figures which accompany it.

DESCRIPTION OF THE DRAWINGS

The specific features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:

FIG. 1 is a cross-sectional view of an inductively coupled RF plasma etch reactor with a dome-shaped chamber employing a cleaning electrode.

FIG. 2 is a cross-sectional view of an RF plasma etch reactor constructed in accordance with a preferred embodiment of the present invention.

FIGS. 3A-F are generalized cross-sectional views of RF plasma etch reactors constructed in accordance with a preferred embodiment of the present invention employing electrically isolated, separately powered, inductive antenna segments .

FIGS. 4A-B are generalized cross-sectional views of RF plasma etch reactors constructed in accordance with a preferred embodiment of the present invention employing electrically isolated, separately powered, inductive antenna segments and shielding elements.

FIG. 5 is a generalized cross-sectional view of an RF plasma etch reactor constructed in accordance with a preferred embodiment of the present invention employing electrically isolated, separately powered, inductive antenna segments and a magnetic field generator which produces a magnetic blocking field. FIG. 6 is a generalized cross-sectional view of an RF plasma etch reactor constructed in accordance with a preferred embodiment of the present invention employing variable aspect inductive antenna segments comprising conductors surrounded by a jacket and secured to the reactor wall.

FIG. 7A is a cross-sectional view of inductive antenna segments in accordance with a preferred embodiment of the present invention comprising conductors surrounded by a jacket and secured to the top wall of the reactor.

FIG. 7B is a cross-sectional view of the inductive antenna segments of FIG. 7A attached to the ceiling of the processing chamber without process gas ports.

FIG. 7C is a cross-sectional view of the inductive antenna of the present invention having an alternate jacket geometry so as to form "T" shaped gaps.

FIG. 8 is a cross-sectional view of inductive antenna segments in accordance with a preferred embodiment of the present invention employing a dummy ring located between inductive coil antenna segments.

FIG. 9 is a top view of an inductive antenna with a partial cut away to depict a possible conductor layout and to depict an antenna segmented into radial arcuate sections and secured to a support member.

FIG. 10 is a schematic view of an antenna in accordance with a preferred embodiment of the present invention showing a possible electrical interconnection.

FIG. 11 is a schematic view of an antenna in accordance with a preferred embodiment of the present invention showing a possible electrical interconnection. FIG. 12 is a schematic view of an antenna in accordance with a preferred embodiment of the present invention showing a possible electrical interconnection.

FIG. 13 is a generalized cross-sectional view of an RF plasma etch reactor constructed in accordance with a preferred embodiment of the present invention employing variable aspect inductive antenna segments comprising conductors surrounded by a jacket and secured to the side wall of the reactor.

FIG. 14 is a generalized cross-sectional view of an RF plasma etch reactor constructed in accordance with a preferred embodiment of the present invention employing inductive antenna segments comprising variably positioned conductors surrounded by a constant aspect jacket secured to the top and side walls of the reactor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description of the preferred embodiments of the present invention, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.

The problem of reduced inductive coupling of RF power into the chamber of a plasma etch reactor due to the build-up of conductive etch by-products on the interior walls of the chamber can be approached in several ways. For example, a self cleaning process can be employed wherein the chamber walls are cleaned of conductive deposits during the etch process itself. This self cleaning process involves the use of RF powered electrodes which replace portions of the chamber walls. As shown in the reactor having a dome-shaped chamber 10 and inductive coil antenna 12 of Fig. 1, such an electrode 36 can be disposed at the top of the chamber 10 in a central void located at the apex of the coil 12'. The electrode 36 is energized via an RF power generator 38 through a matching network 40. The electrode 36 is energized via the generator 38 at a low voltage during etch processing to keep conductive etch by-products from forming on the electrode 36 or immediately adjacent areas. This voltage would be low enough that the energized electrode 36 does not significantly affect the etching process. However, the further away from the electrode 36 that an area of the chamber wall is, the less the cleaning effect and the more likely conductive deposits will form. Therefore, to be effective, multiple electrodes would have to be employed and placed close enough to each other that the entire interior surface of the chamber adjacent the coil is protected from the formation of conductive etch by-products. However, it has been found that the electrode voltage has to be kept at such a low level, so as to not substantially affect the etch process, that electrodes merely placed at the top and bottom of the coil 12 are not sufficient to keep the entire chamber wall adjacent the coil 12 free of deposits. Further, it is not possible to place electrodes on the interior wall adjacent (i.e. directly underneath) the coil 12 without interfering with the inductive coupling of power in to the reactor chamber 10. Accordingly, this approach, while reducing the problem, cannot completely eliminate it, and so is not as preferred as other approaches to be discussed later in this specification.

Another approach to the conductive etch by-product deposit problem involves heating the chamber walls to a temperature above the deposition temperature of the particular conductive etch byproduct causing the problem. However, this approach has drawbacks as well. The highest practical temperature that the chamber wall of a typical inductively-coupled etch reactor, such as the one depicted in Fig. 1, can be heated to is about 200 degrees Centigrade. Higher temperatures would degrade the organic seals usually employed to seal the various access points to the chamber. Some of the previously-described metals which are to be etched produce conductive by-products which have deposition temperatures exceeding 200 degrees Centigrade. For example, the etching of both copper and platinum produce conductive by-products with deposition temperatures exceeding approximately 600 degrees Centigrade. It might be possible to replace the typically used organic seals with ones made of metal. However, such metal seals are usually only effective for one etch operation because they are susceptible to changes in metallic structure or physical deformation at high temperatures which would degrade their ability to seal the chamber. ^""For example, a typical aluminum seal would deform at approximately 400 degree Centigrade, and could not be reused. The need to replace the seals in the etch reactor after every etch operation would be unacceptable to most users. Thus, while this approach is useful when the deposition temperature of the conductive etch by-product causing the attenuation of inductively coupled RF power is relatively low (e.g. less than about 400 degrees Centigrade if aluminum seals are employed) , a more comprehensive solution is preferred.

Fig. 2 depicts an RF plasma etch reactor constructed in accordance with the most preferred solution to the problem of reduced inductive coupling of RF power due to the build-up of conductive etch by-products on the interior walls of the reactor chamber 10'. Like conventional inductively coupled plasma etch reactors, there is a vacuum chamber 10', a pedestal 16 for supporting a workpiece 14, a bias RF power generator 22 and associated impedance matching circuit 24 for imposing a RF bias on the workpiece 14, and a vacuum pump 28 to evacuate the chamber 10' to a desired chamber pressure. However, the inductive coil antenna 44 is quite different. Rather than being wrapped around the outside of the reactor chamber 10', the coil 44 is disposed or installed inside the chamber. This places the coil beyond any conductive etch by-product coating on the interior walls of the chamber. Thus, the conductive coating cannot attenuate the magnetic field generated by the energized coil 44 (or at least the portion directed into the plasma region of the chamber) , and so there is no decrease in the inductive coupling of RF power to this region. As a result, there is no detrimental effect on the plasma characteristics or difficulty in igniting and maintaining a plasma within the chamber. Of course, since the coil 44 is energized during etch processing, there will be no deposition of etch by-products thereon which could interfere with the inductive coupling of power. Further, since the antenna is inside of the chamber it can generate a plasma using a lower level of RF power because the impedance of the chamber walls need not be overcome as is the case with a conventional inductively coupled plasma etch reactor.

The interior coil 44 is shown in Fig. 2 as having a unitary, planar configuration and is disposed near the top of the chamber 10'. This embodiment of the coil is unitary in that it is constructed from an electrically continuous, spirally wound conductor. However, the coil can alternately take on a variety of shapes and locations within the chamber. In addition, the coil can be segmented, with the segments being electrically isolated and separately powered. Figs. 3A-F are examples of etch reactors employing these segmented, separately powered, interior coils. All these examples depict a coil having a first coil segment 46a-f and a second coil segment 48a-f. The first coil segment 46a-f is energized via an external RF power source having a first RF power generator 50a-f and first impedance matching network 52a-f. The second coil segment 48a-f is energized via an external RF power source having a second RF power generator 54a-f and second impedance matching network 56a-f. Separate power sources are shown supplying RF power to each of the coil segments 46a-f, 48a-f as well as the pedestal 16. This allows the amount of power, as well as the frequency to be individually set for each of these elements. For example, different RF power levels or frequencies may be applied to different coil segmeTits by the separate RF power generators connected thereto to adjust plasma ion density spatial distribution. A common power source could also be employed for any number, or all, of the aforementioned elements if desired. Preferably this common source would have the ability to supply RF power to the individual elements at different power levels and frequencies.

It is noted that the number of turns of each coil segment implied by the their illustration in Figs. 3A-F (as well as the single coil of Fig. 2) is for representational purposes only.

The coil or coil segments may actually have any number of turns .

As can be seen the primary difference between the reactors shown in Figs. 3A-F, respectively, is the shape and location of the coil segments 46a-f, 48a-f. In Fig. 3A, the first coil segment 46a is planar in shape and is disposed near the top of the chamber 10', while the second coil segment 48a is cylindrical in shape and located near the side walls of the chamber. In Fig. 3B, both coil segments 46b, 48b are planar and located near the top of the chamber 10', with the first segment 46b being concentric with and disposed within a central void of the second segment 48b. Fig. 3C depicts a coil segment configuration much the same that of Fig. 3B, except the second coil segment 48c is located further down in the chamber closer to the workpiece 14. In the reactor of Fig. 3D, the first coil segment 46d is planar in shape and is disposed near the top of the chamber 10', while the second coil segment 48d has an inverted, truncated, conical shape which is located so as to surround the workpiece 14. The reactors of Figs. 3A-D are shown with cylindrical shaped chambers 10'. However, this need not be the case. Since the inductive coil antenna resides inside the chamber 10', the shape of the chamber can be tailored to optimize its effect on the plasma. In other words, the shape of the coil is no longer a key consideration in the design of the chamber, therefore, the chamber can be configured in any appropriate shape, preferably one which will enhance the particular plasma characteristic desired for the etch operations to be performed with the reactor.

For example, Figs. 3E-F depict reactors with truncated conical shaped chambers 10'. In Fig. 3E, the first coil segment 46e is planar and disposed near the top of the chamber 10', while the second segment 48e has a truncated, conical shape and is located adjacent the side walls of the chamber 10'. The reactor of Fig. 3F is similar to that of Fig. 3E with the exception that the second coil segment 48f has an inverted, truncated, conical shape and is located further down in the chamber 10' nearer the workpiece 14. Of course, many other chamber shapes are possible, for example, the chamber could be dome shaped, or it could have an aggregate shape incorporating two or more of the previously mentioned dome, cylindrical and truncated conical shapes. The particular shape of the chamber should be selected to optimize the desired plasma characteristics for the type of etching being performed.

Figs. 3A-F depict inductive coil antennas having two individually powered coil segments. However, the present invention is not limited to just two segments. Rather any number of individually powered segments could be employ. Further, like the shape of the chamber, the coil or coils segments can take on any advantageous shape. As the inductive coil antenna is disposed inside the chamber 10', it can take on any shape desired, independent of the shape of the chamber. Thus, the previously described tradeoff between the shape of the coil and the chamber is no longer a concern. It is also noted that although only planar, cylindrical, and truncated conical shaped coil and coil segments are depicted in Figs. 3 and 4A-F, the present invention is not limited to these shapes. Rather the coil or coil segments can have any advantageous shape, such as a dome shape or an aggregate of two or more of the aforementioned planar, dome, cylindrical and truncated conical shapes. In addition, it is not intended to imply that the location within the chamber where the coil or coil segments reside is limited to the depicted embodiments. The coil or coil segments can be located and oriented in any advantageous configuration desired. A significant advantage of placing the inductive coil antenna within the chamber is that, without the restrictions caused by the shape of the chamber, the power deposition can be optimized for the intended etch processes to be performed within the chamber. Placing the coil or coil segments inside the chamber allow considerable flexibility in shaping the power deposition. Such factors as the shape, location, and orientation of the coil or each coil segment can be chosen so as to create an optimal power deposition pattern within the chamber. These factors can also be chosen in view of the expected diffusion characteristics and life spans of the etchant species involved in the particular etch process envisioned for the reactor. Further, the amount of RF power supplied to the coil or coil segments can be varied to tailor the power deposition and etchant species distributions, thereby allowing the same coil configuration to accommodate the diffusion characteristics of a wider range of etchant species types. The specific coil or coil segment configuration and RF power input settings should be selected to optimize the power deposition and etchant species diffusion for the particular etch process to be performed.

In addition to the coil related factors such as shape, location, and orientation which can be manipulated in an effort to optimize the power deposition and etchant species diffusion patterns within the chamber, shielding elements or fields can also be introduced into the chamber to further tailor these patterns. For example, a shielding element or field could be used to decrease the plasma ion energy in a particular region of the chamber. Figs. 4A-B (which correspond to the reactors described in conjunction with Figs. 3A-B, respectively) depict a shielding element 58a-b placed between one or more of the coil segments and the workpiece to affect the power deposition adjacent the element. This shielding element 58a-b preferably takes the form a Faraday-type shield or conductive screen. In either case the shielding element 58a-b is electrically grounded. The grounded element 58a-b attenuates the magnetic field generated by the adjacent coil segment or segments, thereby decreasing the inductive coupling of RF power to the plasma on the other side of the shield. In this way the power distribution in the areas beyond the shielding element 58a-b can be reduced as desired, for example to decrease the plasma ion energy in the region. In Fig. 4A, a cylindrical shielding element 58a is employed adjacent the cylindrical second coil segment 48a to reduce the RF power inductively coupled by this segment to the plasma region in the center of the chamber 10'. This is an example where only one of the coil segments is significantly affected. Fig. 4B illustrates an embodiment where the inductively coupled RF power from multiple coil segments (in this case two) is attenuated using a shielding element 58b. The shielding element 58b is placed horizontally within the chamber below the first and second coil segments 46b, 48b. This horizontal placement causes a reduction in the RF power inductively coupled by each segment 46b, 48b to the plasma region directly overlying the workpiece 14 on the opposite side of the shield element 58b. Thus, the shielding element can be used to affect one or more, even all, of the coil segments employed in the reactor. In addition, more than one shielding element could be employed to accomplish this task, if desired.

An alternative way of manipulating the power deposition is to introduce a second magnetic field into the chamber. As illustrated in Fig. 5, this can be accomplished by the addition of a magnetic field generator 60 outside the chamber 10'. The generator 60, which can include either an electromagnet or a permanent magnet, creates a magnetic field within the chamber 10' which blocks the passage of ions. Thus, if the blocking magnetic field is imposed between the inductive coil antenna 44 (or segments thereof as would be the case in some embodiments of the present invention) and the workpiece 14, ions can be prevented from reaching the workpiece. The stronger the magnetic field, the fewer ions that will be able to pass through and impact the surface of the workpiece. It is preferred that the generator 60 be adjustable so as to vary the strength of the blocking magnetic field. In this way the quantity of ions passing through to the workpiece 14 can be adjusted. Accordingly, plasma characteristics such as ion density and ion energy can be controlled at the surface of the workpiece 14 by adjusting the strength of the blocking magnetic field.

Yet another advantage of placing the inductive coil antenna within the chamber is that the chamber need not be made of an insulative material. As explained previously, the portion of the chamber walls underlying the inductive coil antenna had to be made from a non-conductive material, typically quartz or ceramic, to prevent significant attenuation of the magnetic field generated by the coil which would decrease the inductively coupling of RF power into the chamber. With the coil inside the chamber this problem is no longer a consideration. Therefore, the chamber walls can be made of conductive materials, such as aluminum. Making the chamber walls conductive has many desirable effects. First, as shown in Fig. 2, the chamber 10' can be electrically grounded and serve as the electrical ground for the RF power supplied through the pedestal 16. The surface area of the chamber walls is significantly greater than the previously employed grounded areas. In addition, the interior surface area of the now conductive and grounded chamber walls will greatly exceed that of the RF energized pedestal 16. This will create a larger negative bias voltage, thereby making it feasible to produce a more optimum plasma ion energy and directionality at the surface of the workpiece.

Another advantage of employing conductive chamber walls is that it solves the problem caused by the deposition of conductive by-products wherein the plasma characteristics (e.g. plasma ion energy and directionality) are adversely affected by the voltage shift that occurred when the conductive deposits electrically coupled with the grounded areas of the chamber. Since the chamber walls are already conductive and electrically grounded, the deposition of additional conductive material on the interior surface of the walls is irrelevant and has no effect on the bias voltage or the plasma characteristics.

Yet another advantage that will be discussed in connection with the use of conductive chamber walls is the enhanced cooling capability such walls can afford. For example, chamber walls made of aluminum exhibit a much higher thermal conductivity in comparison to the quartz walls of conventional inductively coupled plasma etch reactors (e.g. 204 W/mK for aluminum compared with 0.8 W/mK for quartz). In addition, as cooling channels 32 are easily formed in aluminum chamber sidewalls and the entire chamber can now be made of aluminum, cooling channels can be distributed throughout the chamber walls. This eliminates the need for air cooling the exterior of the chamber walls as was necessary with a conventional inductively coupled RF plasma etch reactor. Flowing coolant through internal cooling channels is a much more efficient method of heat transfer. Consequently, heat transfer from the chamber interior to coolant fluid flowing in the cooling channels 32 formed in the chamber walls is much quicker. This increased rate of heat transfer allows for much less variation in the chamber temperature. As a result, the chamber temperature can be readily maintained within that narrow range necessary to ensure efficient etch processing and to prevent the cracking and flaking off of contaminating deposits from the chamber walls.

Conductive chamber walls made of metals such as aluminum can, however, have a potential drawback. These materials would tend to sputter under some etch processing conditions. The material sputtered off of the walls could contaminate the workpiece and damage the devices being formed thereon. This potential problem is prevented by forming a protective coating 45 over the interior surface of the chamber walls, as shown in Fig. 2. This coating 45 is designed to be resistant to the effects of the plasma and so prevents the conductive material from being sputtered into the chamber 10'. Further, the coating 45 is designed to have an insignificant effect on the electrical and thermal properties exhibited by the walls. If the chamber walls are aluminum, it is preferred the interior surface be anodized (i.e. coated with a layer of aluminum oxide). The anodized aluminum layer will provide the protective characteristics discussed above. Alternatively, a conductive ceramic material could be chosen to coat the interior walls of the chamber to prevent sputtering and surface reaction on the walls. For example, boron carbide would be an appropriate choice .

A similar sputtering problem exists with the inductive coil antenna or segments described previously. If the coil or coil segments were to be formed of a metal, the unwanted sputtering of this metal by the plasma could contaminate the workpiece, and would quickly erode the coil structure. One solution is to make the coil or coil segments from a "non-sputtering" conductive material, such as a conductive ceramic like boron carbide. Another possibility would be to use a metal core surrounded by a "non-sputtering" coating. For example, an aluminum core covered with a boron carbide jacket. In either embodiment, the coil would be protected from the sputtering effects of the plasma and any contamination of the workpiece prevented. It is also noted that the temperature of the coil during etch processing must often be controlled. If such is the case, the coil can be constructed with a hollow, tube-like structure. This would allow coolant fluid to be pumped through the channel formed by the interior of the coil, thereby cooling the coil and maintaining the desired operating temperature.

It is also possible, as depicted in Fig. 6, to surround the conductor 102 with a non-sputtering jacket 104 which is a poor electrical conductor but a good thermal conductor, such as surrounding with a ceramic such as aluminum nitride. The antenna 100 is then coupled to the ceiling or top wall 112 of the chamber to form a heat exchange channel or conduit 110, which provides a heat flow path between the antenna 100 and the wall 112. It is presently preferred to create the heat exchange conduit 110 by directly coupling the antenna to the wall such as by brazing the antenna 100 to the wall 112 so that heat generated by the antenna is transferred to the chamber wall by conduction. The antenna 100 could also be interlocked with or be otherwise bonded with the wall, such as by screwing, by gluing, or the like, to form the heat exchange conduit.

Coupling the antenna to the wall allows the temperature of the antenna 110 to be regulated by regulating the temperature of the wall. Therefore, the temperature of the antenna 100 may regulated by pumping coolant through channels 114 in the reactor wall 112. Coupling the antenna to the wall 112 with a thermally conductive material and regulating the temperature of the wall, or pumping coolant through the hollow coil as described above, provides a means for regulating the temperature of the inductive coil .

Regulating the temperature of the antenna helps prevent cracking and flaking of the jacket and inhibits cracking and flaking of any contaminating deposits that may accumulate on the surface of the antenna. Cracking and flaking are typically caused by thermal expansion cycles. For example, an unregulated antenna can reach temperatures of 500 degrees centigrade or more and then cool to room temperature. This type of temperature cycle can cause any coating or build-up on the surface of the antenna, or the jacket itself, to crack or flake. If the antenna is located over or near the workpiece, pieces likely will contaminate the workpiece if the temperature is not regulated. Furthermore, the jacket and conductor are less likely to separate if the temperature of the antenna is regulated. The optimum operating temperature of the antenna is dependent on the type of etch by-product and the composition of the antenna. It easily can be determined empirically and is expected to be about from 100 to 300 degrees centigrade.

As discussed above, a good thermal conductor should be selected for the construction of the antenna. A good thermal conductor is selected that will transfer heat rapidly so that the antenna does not heat unevenly. Uneven heating will cause thermal stresses on the antenna 100 which will reduce its reliability. As current passes through the conductor 102, heat is generated by the conductor which heats the antenna 100. Since the antenna is cooled by the wall 112, a temperature gradient may build within the antenna 100. By using a good thermal conductor, the temperature gradient within the antenna can be reduced so that the antenna is not subject to thermal stresses sufficient to degrade the antenna 100 or degrade the antenna to wall coupling 110. Furthermore, the thermal conductivity of the antenna must permit the temperature of the antenna to be optimized, as discussed above, so that the antenna or by-products do not flake, and so that deposition of by-products on the surface of the antenna can be controlled.

Forming the jacket of a poor electrical conductor provides a means for coupling the conductor 102 to the electrically conductive chamber wall 112 without providing a path to ground through the grounded chamber wall 112. If the antenna is formed of a electrically conductive ceramic material, such as boron carbide as discussed above, the jacket could take the form of an electrically insulative layer formed between the electrically conductive antenna material and the electrically conductive chamber wall 112. The thermally conductive layer thus provides the heat exchange conduit formed by the antenna to chamber wall coupling and thereby provides the means for regulating the temperature of the inductive antenna by regulating the temperature of the chamber wall.

The aspect of the antenna 100 can be varied, as depicted in Fig. 6, so that the conductor 102 location within chamber forms a desired antenna shape as discussed with reference to Figs. 3A-F above. Turning to Fig. 7A, it is presently preferred to form the profile of the jacket 104 in the shape of a block and to embed or deposit the conductor 102 within the jacket 104. The jacket 104 could completely surround conductor 102 as shown, or the jacket 104 could surround the conductor so that only portions of the conductor likely to sputter into the chamber are covered, thereby preventing contamination of the chamber.

The conductor can be positioned so that it forms a flat strip having two sides 103a & 103b and two edges 105a & 105b completely surrounded by jacket 104, as depicted in Fig. 7A. The conductor can be oriented such that one of the sides 103b, or one of the edges 105b faces the plasma 101. Or, the conductor can be positioned so that it forms a square or rectangular shape. The conductor 102 could also be surrounded so that a portion of the conductor is exposed to the plasma if the process is such that sputtering, or corrosion, of the conductor is not a serious concern.

Furthermore, the electrically non-conducting jacket 104 could surround the conductor 102 only partially so that it can be coupled to the electrically conductive wall, while another material, could surround the conductor in part.

Fig. 7A also shows the brazing bond 110 coupling the antenna 100 to the reactor wall 112. The brazing bond 110 allows heat to exchange between the antenna 110 and the wall 112. The temperature of the jacket 104 and of the conductor 102 is regulated by pumping coolant through channels 114 in the wall 112. Bonding the antenna 100 to the wall 112 by brazing is but one way to form the heat exchange conduit between the antenna and the wall. In the embodiment of Fig. 7A, the heat exchange conduit between the antenna and the wall must have sufficient thermal conductivity to allow regulation of the temperature such that thermal expansion cycles of the antenna do not cause cracking or flaking of the antenna 100 or cause decoupling of the antenna-to-wall coupling.

It is presently preferred to form the antenna of^" a plurality of nested annular rings. Gaps 120 are formed between the rings 100a & 100b and 100b & 100c. Preferably, the gap size is large enough so as to prevent conductive etch by-product from forming between the rings and electrically connecting the rings. Furthermore, the gap size is selected so that plasma 101 is not generated between the rings. The maximum gap size, therefore, is governed by the Debye ' s equation as follows: λ_De = ( ε₀T_e / en₀ ) ^{1 2}

where λ_De is the Debye length; εo is the permittivity of free space, 8.854 x 10-12 F/m;

T_e is the electron temperature ~ 4V; e is the nonsigned charge of an electron; no is the plasma density . In typical applications, the gap is formed having parallel side walls separated by a width of between about 0.025 mm to 1 mm.

Turning to Fig. 7B, to inhibit conductive etch byproduct from joining the segments, the gap 120 between antenna segment 100a and 100b typically is formed having parallel side walls 121a & 121b with an aspect ratio larger than 5. In an alternate embodiment shown in Fig. 7C, the jacket may be formed so that the shape of the gap 120 forms a "T" so as to inhibit conductive byproduct from joining the segments. In either case, the length of the side wall 121 is sufficiently large as compared to the width of the gap so as to inhibit conductive byproduct from joining the segments. If desired, gas ports 122, shown in Figs. 6 & 7A may be located so as to deliver process gas via the gaps 120 between the rings 100. Although Figs. 6-8 depict the gaps 120 extending completely through the antenna 100, the gaps 120 may be formed as discussed above so that they extend only part way into the antenna 100. As such the plasma reactor of the present invention may employ an antenna 100 having a unitary structure. Furthermore, as discussed further below, the antenna may be attached to an intermediate member or a support member which may be attached to the chamber wall.

Turning to Fig. 8, another feature of the present invention is to provide an antenna which is easily cleaned. As such, dummy rings may be provided between the antenna rings. The dummy rings are removably located between the annular rings of the antenna. The dummy rings may be removed during cleaning so that etch byproduct that may build-up on the side of the antenna coil in the gap 120 can be easily removed by gases during the cleaning process. The removed dummy rings may be cleaned before re- installation or a new set of dummy rings may be installed before workpiece processing.

In Fig. 8, the dummy ring lOOe is releasably or removably attached to the chamber wall 112, such as by using a mechanical interlock 107, so that it may be removed when the reactor chamber is cleaned. As an alternative embodiment, the dummy rings could be removably attached to the antenna rings or to a support structure as discussed below.

Removable dummy rings allow by-products deposited in the gaps 120 between the dummy ring lOOe and the annular rings lOOd

& lOOf to be more easily removed during the cleaning process.

The gap size between the dummy rings and the antenna ring segments is selected in the same manner as discussed above. -

Turning to Fig. 9, in addition to segmenting the antenna into individual rings, it is also desirable to separate the surface of the individual rings 100, such as by segmenting each of the rings or turns to form arcuate antenna segments 130, 132 & 134. Separating the exposed surface of the antenna reduces eddy currents that can form in the conductive etch by-product deposited on the surface of the antenna.

Eddy currents caused by conductive etch by-product on the surface of the antenna 100, attenuate the power coupling between the antenna and the plasma. Therefore, as a workpiece is processed, the power delivered to the plasma gradually diminishes. This affects plasma characteristics such as density and plasma etch rate. As workpiece processing necessitates precise control of plasma characteristics, variations in antenna power coupling degrades workpiece processing. By segmenting the antenna into arcuate segments, eddy current is not able to flow around the annular coil. As such, segmenting the antenna provides a means for reducing eddy currents formed in conductive etch by-product deposited on the surface of the antenna and improves inductive power coupling to the plasma.

The surface of the arcuate segments exposed to conductive etch by-product, therefore, are separated by radial gaps 140.

The radial gap size is selected, as discussed above, so that the radial gaps are large enough to inhibit conductive etch byproduct from electrically joining the arcuate segments and small enough to inhibit plasma from being generated between the arcuate segments 130, 132 & 134. Although the radial gaps may completely separate portions of the antenna into arcuate segments, it is possible to form the radial gaps so that they only extend "part way through the antenna so that the antenna has a unitary structure .

Radial gaps, or any type of gap for separating the exposed surface of the antenna may be provided to inhibit current from flowing in the conductive deposits. Furthermore, it is also possible to partially surround or cover the exposed surface of the antenna with several solid pieces of either conductive or nonconductive materials to inhibit the electrical connection of deposits. The gaps between the pieces of the covering or partial jacket material are formed as discussed above. With this embodiment, it is possible as discussed above, to partially surround the conductive portion of the antenna so that it can be coupled to the electrically conductive chamber wall, while another material could surround or cover the surface of the antenna otherwise exposed to plasma so as to inhibit eddy currents in conductive deposits on the antenna. Furthermore, the jacket or covering could be formed of a non-sputtering material and protect the underlying portion of the antenna from sputtering.

In the embodiment of Fig. 9, the arcuate segments 130, 132 & 134 are attached to a support member 150 while jumpers 136 & 138 are used to electrically connect conductors 131, 133 & 135.

The support member 150 could also be used to couple the antenna 100 to the wall or to form the heat exchange conduit. In Fig. 9, support member 150 is depicted with three annular rings for illustration purposes. Support member 150, however, could have any number of rings attached to it and could also be used as a support for removable attachment of the dummy rings discussed above. ^~"

The antenna of the present invention could be made of a single coil or multiple coils. Various conductor 102 interconnections could be used, such as those illustrated in Figs. 10-12, to adjust ion uniformity. Furthermore, the individual segments could be independently controllable such as by connecting the segments to independent power sources.

Fig. 13 shows possible locations of the antenna segments 200 & 300. Antenna 300 is shown attached to the ceiling of the processing chamber. Dummy rings 300b, 300d & 300f are located between antenna segments 300a, 300c & 300e. The antenna 200 is secured adjacent the side wall of the reactor chamber. In this embodiment, the antenna rings 200a-e are shown attached together at the peripheries of the rings so that the antenna 200 forms a single structure. The gaps 120 between the rings 200a-e are formed as discussed above and do not completely separate the rings 200a-e. The antenna 200, therefore, may be attached to the chamber wall by only the top ring 200e or by only the bottom ring 200a.

With this embodiment, it is also possible to employ antenna supports 211 to secure the antenna within the processing chamber.

This would allow the antenna 200 to be easily removed for cleaning or replacement. In this embodiment, the antenna 200 may be placed in close contact with the wall so that the antenna 200 is thermally coupled to the wall to form the heat exchange conduit allowing heat to exchange between the antenna 200 and the chamber wall. As an alternative, the antenna 200 may placed in the processing chamber so that it couples to, or improves its coupling with, the chamber walls as it heats and expands. In either case, the cooling channels 114 in the chamber wall may^~~be used to regulate the temperature of the chamber and, therefore, provide a means for regulating the temperature of the antenna 200.

Fig. 14 illustrates antenna segments 400 & 500 having a constant aspect. In this embodiment, the conductor 102 position, within the non-conducting jacket 104 of antenna segments 400 & 500, forms the desired power deposition as discussed with reference to Figs. 3A-F above. In this embodiment, radial gaps 140 are formed on the surface of the antenna coil 500 exposed to conductive etch by-product. For illustration purposes only a single radial gap 140 is shown in antenna segment 400.

As is obvious to one skilled in the art, there are various possible alternatives for installing the antenna that fall within the scope of the present invention.

Still another advantage of placing the inductive coil antenna within the chamber of an inductively couple plasma etch reactor is that the antenna no longer dictates where the etchant gas ports can be located. As explained previously the etchant gas ports could not be located on the chamber wall adjacent an external inductive antenna because the antenna would physically interfere with the necessary channeling and feed structures needed to supply such a gas injection port with etchant gas. This was disadvantageous because it is often desirable to introduce etchant gas into a region of high power deposition, such as the ones formed just inside the chamber wall adjacent the external antenna. Since the antenna no longer blocks access to the interior of the chamber through the chamber walls, the locations where injection ports can be placed is increased significantly. As a result, gas injection ports can be located so that etchant gas is introduced near areas of high power deposition, or away from these areas, as desired. For example, Fig. 2 shows gas injection ports 26 located adjacent the inductive antenna 44 such that they are able to inject gas into areas 47 of high power deposition near the antenna. Accordingly, there is a much greater versatility in port placement possible with a reactor constructed in accordance with the present invention.

Figs. 7A & 8, illustrate etchant gas ports 122 being located adjacent annular antenna rings. Fig. 7A shows the gas ports 122 between the annular rings 100a and 100b, and between 100b and 100c. The gap 120 between the antenna rings is sufficiently small so that no plasma 101 forms in the gap and sufficiently large so that the gap is not blocked by etch byproduct deposits.

In addition to the advantages of an etch reactor constructed in accordance with the present invention which has been described thus far, it is also pointed out that the reactor could be operated in a capacitively coupled mode, in an inductively coupled mode, or any combination thereof. Referring once again to Figs. 2 and 3A-F, if RF power is supplied to the pedestal 16, without also supplying RF power the inductive antenna 44 or segments 46, 48, the reactor will operate in a capacitively coupled mode. This is not possible in a conventional inductively coupled plasma etch reactor due to the previously-described inadequate area ratio between the pedestal and the conductive anode portion. The area ratios typically found in conventional reactors produce poor capacitive power coupling which has been found insufficient to generate a plasma within the chamber.

Alternatively, RF power could be supplied to the inductive antenna 44 or segments 46, 48, without also supplying RF power the pedestal 16. Thus, the reactor would operate in an inductively coupled mode.

Inductive coupling will be more efficient at pressures ranging between about 1 mTorr and 100 mTorr, while capacitive coupling will be more efficient at pressures ranging between about 100 mTorr and 10 Torr. Some etch processes are best performed at lower pressures consistent with inductive coupling, whereas other etch processes are best performed at the higher pressures consistent with capacitive coupling. Thus, a reactor constructed in accordance with the present invention has a greater versatility than either a conventional inductively coupled or capacitively coupled plasma etch reactor because it can support etch processing over much wider pressure ranges. Additionally, inductive coupling will generate more ions, while capacitive coupling will produce more reactive neutral species. Different etching processes or process steps often call for more ions or more reactive neutral species, depending on the desired result. A reactor constructed according to the present invention can control the composition of the plasma in ways not possible with conventional inductively coupled or capacitively coupled etch reactors because the amount of RF power inductive and capacitive coupled into the chamber 10 can be readily varied by varying the amount of power supplied to the pedestal 16 and internal inductive antenna 44 (or antenna segments 46, 48). For example, some steps of an etch process can be performed with more inductive coupling to create an ion-rich plasma, while other steps can be performed with more capacitive coupling to create a reactive neutrals-rich plasma. Further, the inductive antenna 44 (or segments 46, 48) need not be the only source employed to sustain the plasma. Rather, the plasma can be at least partially sustained via capacitive coupling using the energized pedestal 16. This allows the RF power supplied to the antenna (or segments) to be tailored to produce the desired etchant species concentrations without regard to the power necessary to sustain the plasma.

While the invention has been described in detail by specific reference to preferred embodiments, it is understood that variations and modifications thereof may be made without departing from the true spirit and scope of the invention.

Claims

WHAT WE CLAIM IS :

1. An inductively coupled plasma reactor comprising: a) a reactor chamber having walls; b) an inductive antenna for exciting a process gas to generate a plasma, the inductive antenna being located within the reactor chamber and being coupled to the chamber wall; c) the inductive antenna comprising a conductor surrounded by an electrically non-conducting jacket; and d) a heat exchange conduit formed by the antenna to chamber wall coupling.

2. The inductively coupled plasma reactor of Claim 1 wherein the inductive antenna further comprises a plurality of annular rings.

3. The inductively coupled plasma reactor of Claim 2 wherein the process gas is delivered into the chamber through ports located between the annular rings.

4. The inductively coupled plasma reactor of Claim 2 wherein source power through individual rings is independently controllable.

5. The inductively coupled plasma reactor of Claim 2 wherein a surface of the non-conducting jacket is exposed to conductive etch by-product and wherein the exposed surface of the jacket is segmented such that conductive by-product deposited on the jacket is inhibited from electrically joining the segments.

6. The inductively coupled plasma reactor of Claim 1 wherein the conductor is segmented.

7. The inductively coupled plasma reactor of Claim 6 wherein the conductor segments may be independently controlled.

8. The inductively coupled plasma reactor of Claim 1 wherein the antenna is segmented.

9. The inductively coupled plasma reactor of Claim 8 wherein the antenna segments may be independently controlled.

10. The inductively coupled plasma reactor of Claim 2 wherein the annular rings are arranged so as to form a three dimensional geometry.

11. The inductively coupled plasma reactor of Claim 10 wherein the annular rings form one of the following shapes:

(i) a planar shape, (ii) a cylindrical shape, (iii) a truncated conical shape, or (iv) a dome shape.

12. The inductively coupled plasma reactor of Claim 10 wherein the aspect of the jacket and the position of the conductor within the jacket forms the three dimensional geometry.

13. The inductively coupled plasma reactor of Claim 1 wherein the jacket is block shaped.

14. The inductively coupled plasma reactor of Claim 13 wherein the conductor is a flat strip having an two sides and two edges and wherein the flat strip is oriented such that one of the sides faces the plasma.

15. The inductively coupled plasma reactor of Claim 13 wherein the conductor is a flat strip having an two sides and two edges and wherein the flat strip is oriented such that one of the edges faces the plasma.

16. The inductively coupled plasma reactor of Claim 13 wherein the conductor is square.

17. The inductively coupled plasma reactor of Claim 1 wherein the conductor is at least partially exposed to the chamber.

18. The inductively coupled plasma reactor of Claim 2 wherein a dummy ring is removably located between adjacent annular rings.

19. The inductively coupled plasma reactor of Claim 1 wherein the antenna is coupled by brazing.

20. The inductively coupled plasma reactor of Claim 1 wherein the heat exchange conduit allows the temperature of the antenna to be regulated by regulating the temperature of the chamber wall.

21. The inductively coupled plasma reactor of Claim 1 wherein the chamber walls are electrically conductive.

22. An inductively coupled plasma reactor comprising :_ a) a reactor chamber having walls; b) an inductive antenna for exciting a process gas to generate a plasma, the inductive antenna being located within the reactor chamber, the inductive antenna being secured to the chamber wall; and c) the inductive antenna being secured to the chamber wall so that heat generated by the antenna is transferred to the wall by conduction.

23. The inductively coupled plasma reactor of Claim 22 wherein the inductive antenna further comprises a jacket at least partially surrounding a conductor.

24. The inductively coupled plasma reactor of Claim 23 wherein the jacket is an electrically non-conductive material.

25. The inductively coupled plasma reactor of Claim 23 wherein the jacket is a good thermal conductor.

26. The inductively coupled plasma reactor of Claim 24 wherein the jacket is a good thermal conductor.

27. The inductively coupled plasma reactor of Claim 26 wherein the jacket is comprised of aluminum nitride.

28. The inductively coupled plasma reactor of Claim 26 wherein the jacket is secured to the reactor wall by brazing.

29. The inductively coupled plasma reactor of Claim 28 wherein the antenna is secured to the chamber wall so that temperature of the antenna can be regulated by regulating the temperature of the chamber wall.

30. The inductively coupled plasma reactor of Claim 22 wherein the antenna is secured to the chamber wall so that temperature of the antenna can be regulated by regulating the temperature of the chamber wall.

31. The inductively coupled plasma reactor of Claim 22 wherein the inductive antenna further comprises a plurality of annular rings.

32. The inductively coupled plasma reactor of Claim 31 wherein the process gas is delivered into the chamber through ports located between the annular rings.

33. The inductively coupled plasma reactor of Claim 31 wherein source power through individual rings is independently controllable.

34. The inductively coupled plasma reactor of Claim 24 wherein a surface of the antenna is exposed to conductive etch by-product and wherein the exposed surface of the antenna is segmented such that conductive by-product deposited on the antenna is inhibited from electrically joining the segments.

35. The inductively coupled plasma reactor of Claim 22 wherein the antenna is segmented.

36. The inductively coupled plasma reactor of Claim 35 wherein the antenna segments may be independently controlled.

37. The inductively coupled plasma reactor of Claim 31 wherein the annular rings are arranged so as to form a three dimensional geometry.

38. The inductively coupled plasma reactor of Claim 37 wherein the annular rings form one of the following shapes:

39. The inductively coupled plasma reactor of Claim 31 wherein a dummy ring is removably located between adjacent annular rings .

40. The inductively coupled plasma reactor of Claim 22 wherein the antenna is secured by brazing.

41. The inductively coupled plasma reactor of Claim 22 wherein the chamber walls are electrically conductive.

42. An inductively coupled plasma reactor comprising: a) a reactor chamber having walls; b) an inductive antenna for exciting a process gas to generate a plasma, the inductive antenna being located within the reactor chamber; and c) a means for regulating the temperature of the __ inductive antenna.

43. The inductively coupled plasma reactor of Claim 42 wherein the regulating means comprises a thermally conductive antenna to chamber wall coupling and cooling channels in the chamber wall.

44. The inductively coupled plasma reactor of Claim 42 wherein the regulating means comprises the antenna having a tubular structure with a hollow interior, and wherein a channel formed by the hollow interior is capable of sustaining a flow of coolant therethrough for regulating the temperature of the inductive antenna.

45. The inductively coupled plasma reactor of Claim 43 wherein the antenna comprises a conductor at least partially surrounded by an electrically non-conductive material.

46. The inductively coupled plasma reactor of Claim 44 wherein the material is thermally conductive.

47. The inductively coupled plasma reactor of Claim 45 wherein the material prevents the sputtering of the antenna by the plasma.

48. The inductively coupled plasma reactor of Claim 45 wherein the chamber walls are conductive.

49. The inductively coupled plasma reactor of Claim 48 wherein the antenna is attached to the reactor wall by ^~" brazing.

50. The inductively coupled plasma reactor of Claim 42 wherein the surface of the antenna is exposed to conductive etch by-product and wherein the antenna further comprises a means for reducing eddy currents on the surface of the antenna due to conductive etch by-product deposition.

51. The inductively coupled plasma reactor of Claim 50 wherein the means for reducing eddy currents comprises segmenting the antenna.

52. The inductively coupled plasma reactor of Claim 51 wherein the antenna is comprised of at least on annular ring and wherein the annular ring is segmented.

53. The inductively coupled plasma reactor of Claim 51 wherein the antenna is comprised of at least two annular rings having a gap therebetween.

54. The inductively coupled plasma reactor of Claim 53 wherein the distance of the gap is such that conductive etch by-product is unable to electrically connect the annular rings

55. The inductively coupled plasma reactor of Claim 54 wherein the distance of the gap is such that plasma does not form within the gap.

56. The inductively coupled plasma reactor of Claim 55 wherein the distance of the gap is such that conductive etch by-product is unable to electrically connect the surface of the annular rings with the chamber wall.

57. The inductively coupled plasma reactor of Claim 42 further comprising a means for preventing sputtering of the antenna by the plasma.

58. The inductively coupled plasma reactor of Claim 52 wherein the segments are separated by a segment gap and wherein the segment gap is sized so that conductive etch by product does not electrically connect the segments.

59. An inductively coupled plasma reactor comprising: a) a reactor chamber having walls; b) an inductive antenna for exciting an etchant gas to generate a plasma, the inductive antenna being installed within the reactor chamber; and c) the inductive antenna comprising a non-sputtering _ material and being constructed so as to prevent sputtering of the antenna by the plasma.

60. The inductively coupled plasma reactor of Claim 59 wherein the inductive antenna comprises a conductor at least partially surrounded by a jacket.

61. The inductively coupled plasma reactor of Claim 60 wherein the jacket is an electrically non-conductive material.

62. The inductively coupled plasma reactor of Claim 60 wherein the jacket is a thermal conductor.

63. The inductively coupled plasma reactor of Claim 61 wherein the jacket is a thermal conductor.

64. The inductively coupled plasma reactor of Claim 63 wherein the jacket is comprised of is aluminum nitride.

65. The inductively coupled plasma reactor of Claim 60 wherein the antenna is coupled to the reactor chamber wall.

66. The inductively coupled plasma reactor of Claim 65 wherein the antenna is coupled by brazing.

67. The inductively coupled plasma reactor of Claim 65 wherein the antenna is coupled to the chamber wall so that temperature of the antenna can be regulated by regulating the temperature of the chamber wall.

68. The inductively coupled plasma reactor of Claim 59 wherein the antenna comprises a conductor surrounded by ceramic.

69. The inductively coupled plasma reactor of Claim 68 wherein the ceramic is coupled to the reactor wall by brazing so as to create a heat exchange conduit between the conductor and the chamber wall such that heat generated by the conductor is able to flow to the chamber wall.

70. The inductively coupled plasma reactor of Claim 69 wherein the antenna is coupled to the chamber wall so that temperature of the antenna can be regulated by regulating the temperature of the chamber wall.

71. The inductively coupled plasma reactor of Claim 59 wherein the antenna has a surface exposed to plasma and wherein the exposed surface comprises gaps, and wherein the gaps inhibit conductive deposits from electrically connecting the surfaces separated by the gaps.

72. An inductively coupled plasma reactor comprising: a) a reactor chamber having walls; b) an inductive antenna for exciting a process gas to generate a plasma, the inductive antenna being located within the reactor chamber and being coupled to the chamber wall; and c) the process gas being delivered into the chamber _ through ports, the ports being located adjacent to the inductive antenna.

73. The inductively coupled plasma reactor of Claim 72 wherein the antenna is comprised of a plurality of annular rings and wherein the ports are located between the annular rings .

74. The inductively coupled plasma reactor of Claim 73 wherein the antenna rings form a gap therebetween and wherein the gap is sufficiently small so as to inhibit plasma from forming between the rings.

75. The inductively coupled plasma reactor of Claim 73 wherein the antenna rings form a gap therebetween and wherein the gap is sufficiently large so as to inhibit conductive etch by-product from electrically joining the rings.

76. The inductively coupled plasma reactor of Claim 73 wherein the gap is sufficiently small so as to inhibit conductive etch by-product from electrically joining the surface of the antenna and the reactor wall.

77. The inductively coupled plasma reactor of Claim 74 wherein the gap is sufficiently large so as to inhibit conductive etch by-product from electrically joining the annular rings.

78. The inductively coupled plasma reactor of Claim 74 wherein the gap is sufficiently small so as to inhibit conductive etch by-product from electrically joining the surface of the antenna and the reactor wall.

79. The inductively coupled plasma reactor of Claim 73 wherein the annular rings form a three dimensional geometry.

80. The inductively coupled plasma reactor of Claim 79 wherein the annular rings form one of the following shapes:

81. The inductively coupled plasma reactor of Claim 73 wherein the annular rings comprise conductors at least partially surrounded by non-conducting jackets and wherein the conductors form a three dimensional geometry.

82. The inductively coupled plasma reactor of Claim 81 wherein the conductors form one of the following shapes: (i) a planar shape, (ii) a cylindrical shape, (iii) a truncated conical shape, or (iv) a dome shape.

83. The inductively coupled plasma reactor of Claim 72 wherein the antenna comprises a conductor at least partially surrounded by a non-conducting jacket.

84. The inductively coupled plasma reactor of Claim 83 wherein the antenna is coupled to the chamber wall by brazing the jacket to the wall.

85. The inductively coupled plasma reactor of Claim 72 wherein the antenna has annular segments.

86. The inductively coupled plasma reactor of Claim 85 wherein the surface of the antenna has arcuate sections having radial gaps therebetween and wherein the size of the radial gaps are such that they inhibit conductive etch by-product from electrically joining the sections.

87. The inductively coupled plasma reactor of Claim 72 wherein a surface of the annular antenna is exposed to conductive etch by-product, the exposed surface of the annular antenna being segmented such that conductive by-product deposited on the surface of the antenna is inhibited from electrically joining the segments.

88. The inductively coupled plasma reactor of Claim 73 wherein a dummy ring is located between the annular rings.

89. The inductively coupled plasma reactor of Claim 88 wherein the dummy ring is removably attached to the chamber wall .

90. The inductively coupled plasma reactor of Claim 88 wherein the antenna rings and dummy ring form gaps therebetween and wherein the gaps are sufficiently small so as to inhibit plasma from forming in the gaps.

91. The inductively coupled plasma reactor of Claim 9^~ϋ wherein the gaps are sufficiently large so as to inhibit conductive etch by-product from electrically joining the annular rings and the dummy ring.

92. The inductively coupled plasma reactor of Claim 90 wherein the gap is sufficiently small so as to inhibit conductive etch by-product from electrically joining the surface of the antenna coil and the reactor wall.

93. The inductively coupled plasma reactor of Claim 88 wherein the concentric annular rings and dummy ring form gaps therebetween and wherein the gaps are sufficiently large so as to inhibit conductive etch by-product from electrically joining the annular rings and the dummy ring.

94. The inductively coupled plasma reactor of Claim 93 wherein the gap is sufficiently small so as to inhibit conductive etch by-product from electrically joining the surface of the antenna and the reactor wall.

95. A method for regulating the temperature of an inductive antenna located within the chamber of an inductively coupled plasma reactor, the method comprising: a) selecting an antenna comprising a conductor; b) coupling the antenna to a wall within an inductively coupled plasma reactor chamber so that heat is permitted to exchanged between the antenna and the chamber wall; and - c) regulating the temperature of the chamber wall so as to regulate the temperature of the antenna.

96. The method for regulating the temperature of an inductive antenna of Claim 95 wherein the chamber wall is electrically conductive and wherein the antenna is coupled so that the conductor is electrically insulated from the wall.

97. The method for regulating the temperature of an inductive antenna of Claim 96 wherein the antenna is comprised of an electrical conductor surrounded by an electrically nonconducting jacket.

98. The method for regulating the temperature of an inductive antenna of Claim 97 further comprising coupling the antenna by brazing the antenna to the chamber wall.

99. The method for regulating the temperature of an inductive antenna of Claim 95 wherein regulating the temperature of the chamber wall further comprises flowing coolant through channels in the chamber wall.

100. The method for regulating the temperature of an inductive antenna of Claim 95 wherein the temperature of the chamber wall is regulated so as to inhibit flaking of the antenna due to thermal expansion cycles.

101. An inductively coupled plasma reactor comprising: a) a reactor chamber having walls; b) an inductive antenna having a surface which is exposed to plasma; and c) the surface of the antenna being separated by at least one gap, the gap being such that it inhibits etch byproduct from electrically joining the separated surfaces.

102. The inductively coupled plasma reactor of Claim 101 wherein the inductive antenna comprises a conductor and an electrically non-conducting layer.

103. The inductively coupled plasma reactor of Claim 102 wherein the inductive antenna is coupled to the reactor chamber wall so as to allow heat to transfer from the inductive antenna to the reactor chamber wall for regulating the temperature of the antenna.