WO1996030929A1

WO1996030929A1 - Sputter etching apparatus with plasma source having a dielectric pocket and contoured plasma source

Info

Publication number: WO1996030929A1
Application number: PCT/US1995/014433
Authority: WO
Inventors: Ebrahim Ghanbari
Original assignee: Materials Research Corporation
Priority date: 1995-03-24
Filing date: 1995-11-09
Publication date: 1996-10-03
Also published as: US5556521A; GB9717174D0; TW277141B; CA2213771A1; GB2316530B; GB2316530A; AU4363796A

Abstract

Apparatus (10) for sputter etching a substrate (14) includes a processing chamber (16) with a plasma source (24) coupled to the top of the processing chamber (16) to seal the chamber and create a plasma therein. The plasma source (24) comprises a dielectric plate (30) having a generally centered pocket (40) with a concave outer surface (43) and a convex inner surface (41) which physically extends into the processing chamber (16) toward a substrate (14). An inductive coil (42) is positioned outside the chamber (16) generally inside the pocket (40) and adjacent the concave surface (43) and is preferably contoured to conform to the concave outer surface (42) to form an inductive source relative to the substrate (14). The contoured inductive coil (42) couples energy through the pocket (40) to create a high density uniform plasma of ionized particles proximate a substrate (14) in the chamber (16).

Description

SPUTTER ETCHING APPARATUS WITH PLASMA SOURCE HAVING

A DIELECTRIC POCKET AND CONTOURED PLASMA SOURCE Field of the Invention This patent relates generally to sputter etching of a

substrate using an ionized gas plasma, and specifically to a sputter etching apparatus with a unique plasma source configuration for producing a dense uniform plasma and a high uniform etch rate over large substrates with small device dimensions. Background of the Invention

In the processing of semiconductor substrates or wafers into integrated circuits, sputter etching is often used to remove a layer of material from the uppermost substrate surface. The process of sputter etching is generally known and utilizes ionized particles of a charged gas plasma to bombard the surface of a substrate and dislodge or "sputter" away substrate particles from

the surface.

More specifically, the substrate to be etched is

supported on an electrically charged support base or electrode

within a vacuum-sealed processing chamber whereon the substrate

develops an electrical charge or bias. A plasma gas is introduced

into a discharge chamber opposite the surface of the biased

substrate, and RF energy is generally inductively coupled to the gas

such as through a coil so that an induced electric field is created

inside the discharge chamber. That is, large current flow in the coil

produces changing RF magnetic flux which penetrates into the

discharge chamber. These changing RF magnetic fields result in

changing electric fields in the discharge chamber. The energy from

the induced electric field inside the chamber ionizes the gas

particles. The ionized particles of the gas and free electrons

collectively form what is referred to as a gas plasma or plasma

cloud. The substrate is biased negatively to collect the positively charged particles from the plasma cloud. The positive ionized

plasma particles are attracted to the negative substrate surface,

bombarding the surface and dislodging material particles from the

substrate to sputter "etch" a material layer from the substrate surface. Conventionally, inductive energy sources utilized to

create and maintain a plasma inside the chamber have been placed

either inside the processing chamber and in the processing space

surrounding the biased substrate, or have been placed around the

outside of the chamber to surround the processing space.

However, inductive energy sources positioned inside of the

chamber proximate the substrate are subjected to undesired

bombardment by plasma particles during the etch, and are

subjected to the deposition of sputter-etched material particles

thereon. Both conditions detrimentally affect the reliability of the

source operation which detrimentally affects the reliability and

uniformity of the plasma. Therefore, many inductive energy

sources today are positioned externally around the processing chamber.

External inductive energy sources have usually

included a solenoidal-shaped coil which is wound around the

outside of the processing chamber to inductively couple energy to

the plasma through the side chamber walls. The processing

chambers and their side walls, therefore, are generally fabricated

from a dielectric substance through which the inductive energy

may pass, typically quartz. However, quartz processing chambers have a drawback in that particles of the substrate material, which

are usually metal, do not readily adhere to quartz, and therefore,

the etched material has a tendency to collect on, but eventually flake off the inside walls of the quartz chamber. Flaking

detrimentally affects the plasma and contaminates the wafer.

Therefore, it is an objective of the present invention to reduce

flaking and substrate contamination during etching.

It is another objective of the present invention to

produce a uniform, high-density plasma over a large area such that

large substrate sizes might be processed. Plasma-aided

manufacturing of ultra large scale integrated (ULSI) circuits requires

a dense uniform plasma over large substrates having diameters of

approximately 200 mm. Existing processing chambers and plasma

energy sources do not adequately address such requirements and

are not able to produce dense uniform plasmas over large areas.

Some sputter etching processes commonly occur at

substrate voltages in the range of approximately 1 ,000 volts ( 1 kV) . However, this relatively high voltage range is inappropriate for

today's state-of-the-art microelectronic devices which have circuit

and device features with dimensions of approximately 0.25 microns

and are more susceptible to surface damage at high wafer charging voltages. As a result, lower wafer voltages, below 500 Volts, are

more desirable, and preferably, voltages lower than 100 Volts are

desirable. However, for an effective etch at such low voltages, a

reliable, efficient and high uniform density plasma is required.

Therefore, it is another objective of the present invention sputter

etch substrates with small device features at low voltages without

reducing the quality of the etch.

A still further objective of the present invention is to

provide a sputter etch chamber and plasma source which are

efficient, reliable and easy to repair and maintain. It is also an

objective of the invention to produce dense uniform plasmas for a

uniform etch rate at low pressures in the range of approximately 1

mTorr.

Summary of the Invention

The above-discussed objectives are addressed by the

sputter etch apparatus of the present invention, which utilizes an

inductive plasma source with a shaped pocket and contoured coil.

The inductive plasma source comprises a dielectric plate which

seals the top of a processing chamber and has a centrally aligned

non-conductive pocket portion or pocket with a generally

concave outer surface and a generally convex inner surface which extends into the processing space inside of the processing

chamber. An inductive coil is positioned outside of the chamber

and is shaped within the concave outer surface of the pocket to

have a generally convex shape in the direction of the processing

space and the substrate. The pocket and the contoured coil extend

partially inside of the chamber and are effective to produce a dense

uniform plasma in the processing space. The coil construction

design also effects the plasma uniformity. For example, a spiral

coil, zig-zag coil or single-turn coil might be utilized to form the

convex shape. Also coils having thin or flat wires with cross-

sections that are not circular may be utilized.

The inductive coil is coupled to an RF power supply

operating preferably at approximately 450 KHz, and is contoured or shaped within the pocket of the dielectric plate such that it extends

partially into the processing space to present a generally convex-

shaped coil opposite a biased substrate. Preferably, the coil is

contoured to closely follow the contour of the outer concave

surface of the pocket but may be contoured to configure generally

to the shape of the pocket. The substrate is biased by a substrate

support which is connected to an RF power supply operating

preferably at approximately 1 3.56 MHz. The pocket and the contoured inductive coil are operable to produce a dense uniform

plasma over a wide area, thus yielding a uniform etch across

wafers which are eight inches (200 mm) or greater in diameter. A

dense uniform plasma is produced at low pressures around 1

mTorr, and the invention is effective to produce reliable, efficient

etches at low substrate bias voltage levels of approximately 50

Volts.

In one preferred embodiment of the invention, RF

tuners are utilized with the substrate RF power supply and the coil

RF power supply in order to minimize reflected power from the

inductive coil and the substrate support to achieve high electrical

efficiency. An electrostatic shield, preferably made of a thin metal

mesh, is positioned in the pocket between the pocket and the

inductive coil and is generally contoured with the pocket in order to

reduce the capacitive energy coupling of the coil to the plasma and

to thereby raise the efficiency of the inductive energy coupling.

To selectively vary the uniformity and density of the

plasma, the dimensions of the pocket and specifically the shape

and degree of curvature of the convex inner surface are varied

along with the corresponding configuration of the contoured

inductive coil within the pocket. In accordance with the principles of the present invention, the pocket shape and coil configuration

may be tailored to a specific processing chamber or substrate

element in order to produce a dense uniform plasma proximate the substrate. It has been experimentally determined that increasing

the depth of the pocket into the processing space and the degree

of curvature of the convex inner surface and increasing the

corresponding depth of the contoured coil tends to improve the

uniformity of the plasma within the processing space.

The dielectric plate, pocket and the inductive coil are

positioned at the top of the metal processing chamber and are

generally centrally disposed with respect to the chamber to extend

into the chamber and thereby inductively couple energy to the

plasma. Since the inductive coil is not wound around the chamber

to surround the processing space, the body of the chamber may be

made of metal or some other conductive material and is preferably

stainless steel. The sputter etched material adheres more readily to

metal than to quartz, thus reducing flaking and contamination of

the substrate. Alternatively, shields might be positioned within the

processing space to surround the wafer and receive the sputter

etched material without concern that the shield material, such as

metal, would short circuit the inductive coupling between the coil and the plasma. The metal chamber walls may be periodically

cleaned of the deposition material, while the metal shields might be

removed and replaced with clean shields for further etching.

In an alternative embodiment of the invention, a

magnetic ring surrounds the metallic chamber and the wafer and

wafer support. The magnetic ring has alternating north/south

magnetic regions around its circumference and induces a magnetic

field around the chamber to confine the plasma and increase the

plasma density proximate the substrate. The magnetic ring also

increases the uniformity of the plasma by preventing plasma

diffusion and leakage into the chamber walls.

The present invention operates to provide dense

uniform plasmas at low voltage and low pressure, and is

particularly suitable for etching semi-conductor devices with 0.25

micron dimensions without damage to the devices. Furthermore,

the sputter etching apparatus of the present invention utilizes a

design which is easy to service and maintain. The plasma

produced by the plasma source is stable and repeatable and

produces a highly uniform etch rate across large substrates. These

and other features are more readily apparent from the brief description of the drawings and the detailed description of the

invention set forth hereinbelow.

Brief Description of the Drawing

The accompanying drawings, which are incorporated

in and constitute a part of this specification, illustrate embodiments

of the invention and, together with a general description of the

invention given above, and the detailed description of the

embodiments given below, serve to explain the principles of the

invention.

Fig. 1 is a schematic view, in partial cross-section, of

the sputter etching apparatus of the present invention showing the

inductive plasma source;

Fig. 2 is a schematic view, in partial cross-section, of

an alternative embodiment of the inductive plasma source of the

present invention shown with a plasma-confining magnetic ring;

Fig. 2A is a schematic top view of the magnetic ring

of Fig. 2.

Fig. 3A is a schematic diagram of the gas flow

components for delivering sputtering gas and backside heating gas

to the sputter etching apparatus of Figures 1 and 2; Fig. 3B is a timing chart illustrating operation of the RF

power supplies and gas supply components for pressure burst

ignition of a plasma in operation of the present invention.

Detailed Description of Specific Embodiments

Referring to Fig. 1 , a sputter etching apparatus 10 of

the present invention is illustrated utilizing a the unique inductive

plasma source 1 2 of the invention for sputter etching a substrate

wafer 14. The sputter etching apparatus 10 comprises a stainless

steel processing chamber 1 6 which includes a base 1 8 and a

substrate support or platen 20 to hold substrate 1 4 inside of the

chamber 1 6 while it is being sputter etched.

The substrate support 20 is coupled to an RF power

supply, including an RF tuner 22, and preferably, a 1 3.56 MHz

source 24. The source may operate in a range of approximately

1 MHz to 1 5 MHz for sufficient biasing of the substrate. Source

24 biases substrate 14 to produce sputter etching as described

further hereinbelow. Substrate support 20 is also coupled to a

backplane heating gas supply 26 for providing backplane gas to

heat or cool substrate 14. Substrate support 20 preferably

includes channels formed therein (not shown) for distributing the

heating gas uniformly over the backside of the substrate 14. Processing chamber 1 6 is closed and sealed at the top

end by a dielectric plate or window 30 which couples to the

stainless steel chamber 1 6 for a vacuum-tight seal. A vacuum

pump 32 is coupled to the processing chamber 1 6 through base 1 8

to vacuum the internal processing space 34, which is created

adjacent substrate 14 by processing chamber 1 6 and dielectric

plate 30. A gas dispersing ring 36 is positioned around the top of

processing chamber 1 6 adjacent dielectric plate 30 and is coupled

to a plasma gas supply 38. The gas dispersing ring 36 disperses

the plasma gas uniformly around the processing space 34, and

specifically around substrate 14.

In accordance with the principles of the present

invention, the dielectric plate 30 includes a generally non-

conductive pocket portion or pocket 40, which is centrally disposed

in the plate 30 and extends downwardly from the top of chamber

1 6. Pocket 40 has a generally convex inner surface 41 which

projects into processing space 34 toward substrate 14. Preferably,

the entire dielectric plate 30 is non-conductive, but it is particularly

critical that pocket 40 be non-conductive despite the construction

of the remaining portions of the plate 30. The non-conductive

pocket 40 extends from dielectric plate 30 into processing space 34 toward the substrate support 20 and substrate 14. To provide

energy to ignite and sustain a plasma within the processing space

34, an inductive coil 42 is positioned outside the chamber 1 6

within the non-conductive pocket 40 of dielectric plate 30. As

illustrated in Figure 1 , inductive coil 42 is preferably wound around

inside pocket 40 and is contoured to follow the generally outer

concave surface 43 of pocket 40.

Pocket 40 preferably has a generally circular

transverse cross section and the coil 42 follows concave surface

43 around pocket 40 for creating a uniform plasma around the

substrate. As the coil 42 follows the outer concave surface 43 of

pocket 40, it forms a contoured coil which is generally convex-

shaped in the direction of substrate 1 4 which extends into the

processing space generally coaxially with pocket 40 as shown in

Fig. 1 . In one embodiment of the invention, the pocket has a wall

thickness T of approximately 1 9 mm, a circumference C of

approximately 102 mm and a length L of approximately 1 50 mm.

The inductive coil 42 is coupled to an RF power

supply, including an RF tuner 44, and preferably, a 450 KHz source

46. A tuner having an operating range from 400 KHz to 1 5 MHz

should be generally useful with the present invention to create a plasma. The RF current from source 46 which flows through

inductive coil 42 induces a time varying RF electric field inside of

the processing space 34. Because pocket 40 is non-conductive,

the inductive electric field from contoured coil 42 is coupled

through pocket 40 and then to plasma gas from supply 38, which

is dispersed around pocket 40 and coil 42 by ring 36. The

inductive electric field produced within the processing space 34

ionizes the gas and creates a discharge of ionized gas particles or

plasma (not shown) within the processing space 34 and proximate

substrate 1 4. Substrate 14 which is biased by RF source 24

attracts the ionized gas particles from the plasma, and the particles,

designated by arrows and reference numeral 48, bombard the

upper surface 1 5 of the substrate 14 to thereby sputter etch

substrate material away from the surface 1 5.

It has been experimentally determined that the shapes

of pocket 40 and contoured inductive coil 42 create a uniform

sputtering plasma having a high density of ionized gas particles 48

proximate the upper surface 1 5 of substrate 1 4. Substrate surface

1 5 is bombarded and the present invention produces a high uniform

sputter etching rate across surface 1 5. It has also been found that the non-conductive pocket 40 and the contoured coil 42, which is wound around the outer concave surface 43 of pocket 40, provide

a high density uniform plasma over a large substrate surface.

Therefore, the present invention is particularly suitable for sputter

etching circular substrates having a diameter greater than or equal

to eight inches, such as 300 mm substrates. Furthermore, it has

been experimentally determined that the plasma produced by the

pocket and contoured coil is stable and is repeatable for more

consistent sputter etching.

The construction design of the coil also would affect

the plasma uniformity. For example, the coil 42 might be a spiral

coil as illustrated in the Figures or a zig-zag coil, or may even be a

single-turn coil. The wire used to form the coil 42 also would

affect the plasma. A wire having a circular cross-section is shown

in the Figures. However, a thin or flat wire might also be utilized in

accordance with the principles of the present invention.

Sputter etching apparatus 10 is electrically efficient

and utilizes RF tuners 22, 44 to reduce the reflected RF power from

the substrate support 20 and inductive coil 42, respectively. In a

preferred embodiment of the invention, a Faraday electrostatic

shield 50 is utilized around the coil 42 adjacent the outer concave

surface 43 of the dielectric plate pocket 40 and between the coil 42 and pocket 40. The electrostatic shield, which is preferably a

thin mesh, reduces the capacitive coupling of the inductive coil 42

to the plasma, and thus raises the efficiency of the coupling of

inductive energy to the plasma.

The uniform distribution of the plasma gas by ring 36

and the dense uniform plasma of the present invention produce

high uniform etch rates across large substrates. Furthermore, the

dense uniform plasma produced by pocket 40 and contoured coil

42 yields good etch results even at low vacuum pressures in the

range of 1 mTorr. Still further, sputter etching apparatus 10 may

be operated at very low wafer biasing voltages in the range of

approximately 50 volts, thus reducing sputter damage to the wafer.

The present invention is particularly suitable for substrates with

very fine devices and integrated circuit features having dimensions

of approximately 0.25 microns.

With pocket 40 and the contoured coil 42 of the

present invention, inductive energy is coupled to the plasma

through the top of chamber 1 6 and through dielectric plate 30.

Therefore, processing chamber 1 6 may be made of stainless steel,

instead of a dielectric material, such as quartz, because inductive

energy does not have to be coupled through the side walls of the processing chamber 1 6. The sputter etched material originating

from substrate 14 adheres more readily to stainless steel than to a

dielectric material such as quartz. As a result, the inner wall 1 7 of

the processing chamber 16 more readily holds the sputter etched

material to prevent flaking of the material into the processing

chamber 34, thus reducing contamination of the sputter etched

wafer. The wall 1 7 may then be cleaned when necessary to

remove the etched material. Alternatively, a metal shield, such as

shield 52, may be utilized between the inner wall 1 7 and substrate

14 to catch sputter etched material. The shield may be metal, such

as stainless steel, or may be made of a dielectric material. Upon

reaching the end of its useful life, the shield 52 may simply be

removed and cleaned or discarded. The shield should not interfere

with the coupling of energy to the plasma, because energy is

coupled through the top of the chamber.

The inductive contoured coil 42 is protected from the

etch environment by pocket 40, and thus, is not exposed to the

sputter etching process. This increases the useful life and reliability

of the coil 42 and yields a more reliable sputter etching process.

To further increase the uniformity and density of the

sputtering plasma, a magnetic ring 56 may be utilized around the processing chamber 1 6 as illustrated in Figure 2. A magnetic ring

56, which preferably utilizes vertically aligned elongated regions

57, 59 of alternating polarity around the circumference of the ring

as illustrated in Figure 2A, creates a magnetic field within the

processing space 34 adjacent the inner wall 1 7 of chamber 1 6.

The magnet 56 and magnetic field created thereby have been found

to prevent plasma leakage by preventing diffusion of ionized plasma

particles into wall 1 7 of chamber 1 6, thus yielding a more uniform

plasma. Furthermore, the magnetic field created by ring 56 has

been found to confine the plasma around support 20 and substrate

14, and thus increases the density of the sputter etching plasma.

The shape of the non-conductive pocket 40 and the

shape of the contoured coil 42 may be varied to improve plasma

characteristics within the processing space 34. By varying the

depth of pocket 40 and the degree of curvature of the inner surface

41 , and by varying the resulting shape of the contoured coil 42,

the plasma uniformity and density are affected. It has been found

experimentally that the greater the pocket depth and the convexity

of the inner surface 41 and the greater the depth of coil 42, the

better the uniformity of the resultant plasma. However, as will be

appreciated by a person skilled in the art, the shape and dimensions of pocket 40 and coil 42 may be tailored according to the

processing chamber 1 6, the internal configurations within the

processing space 34, as well as the size and location of substrate 14. Figure 1 shows an extreme case in which pocket 40 is

generally cylindrical and the coil 42 is contoured and dimensioned

to extend almost the entire length of the processing chamber 1 6 to

terminate very close to substrate support 20 and substrate 1 4.

Figure 2 shows a more shallow pocket 40 and relaxed curvature or

convexity of the inner surface 41 and coil 42. As illustrated in

Figures 1 and 2, the resulting shape of the con-toured coil 42 is

dependent upon the depth and shape of pocket 40 and the shape

of the generally concave outer surface 43. The shape of the coil

42 may range anywhere from solenoidal, as illustrated in Figure 1 ,

to a flatter convex-shaped coil as illustrated in Figure 2. As will be

appreciated, very shallow pockets utilize an inductive coil, which is

almost flat or "pancake" in shape. Fig. 2B shows a top view of the

shape of the coil utilized in Fig. 2.

To explain the operation of the plasma source 1 2 of

the invention, an explanation of the plasma ignition scheme and

etching is helpful. Figure 3A is a schematic diagram of the gas

flow components for delivering plasma gas to the processing chamber 1 6 and backside heating gas to the substrate support 20.

The gas flow components are synchronized to produce a gas

pressure burst for easy ignition of the plasma and to subsequently

create a sufficient gas flow to sustain the ignited plasma.

Figure 3B is a timing chart illustrating the operating

sequence and synchronization of the various gas supply

components illustrated in Figure 3A to produce pressure burst

ignition and a subsequent plasma. The gas flow system includes a

mass flow controller 60 (MFC) for controlling the gas flow rate

from the gas supplies, such as plasma gas supply 38 or backplane

heating gas supply 26. Preferably, the gas used for both purposes

is Argon, and a single gas source may be coupled to mass flow

controller 60. An isolation valve 62 is coupled at the output of the

mass flow controller and may be incorporated with the structure of

the mass flow controller 60. After the isolation valve 62, the gas supply line 64 is split between the backplane branch 65 and a

processing chamber branch 66. A needle valve 68 provides course

adjustment of the gas pressure in the processing chamber 1 6. The

chamber valve 70, in line with needle valve 68, provides a more

precise pressure control of the plasma gas pressure within the

processing chamber 1 6. A backplane valve 71 controls the flow of gas to substrate support 20 for backplane heating of substrate 14

during sputter etching. All of the gas flow components of Figure

3A and RF sources 24 and 46 are preferably coupled to a controller

59 for timed operation, except for needle valve 68 which is

manually opened and closed.

Referring to Figure 3B, the full process interval for

sputter etching a substrate may be divided into a pressure burst

interval denoted by reference numeral 72, a substrate power

interval denoted by reference numeral 73, a soft etch process

interval denoted by reference numeral 74, and a power down

interval denoted by reference numeral 75. As illustrated in line A

of Fig. 3B, a throttle 76, which is coupled to vacuum pump 32 (see

Figs. 1 and 2) is kept closed, and the mass flow controller 60 is

opened for full gas flow at approximately 288 seem, as illustrated

in line B. As illustrated in line C, the gas pressure in processing

chamber 16 begins to steadily rise due to the high flow of gas and

the absence of vacuum pumping. During the pressure build-up

within chamber 1 6, the isolation valve 62, needle valve 68, and the

chamber valve 70 are all open, as illustrated in lines I, H, and G of

Figure 3B in order to allow gas flow into the processing chamber

1 6. During the initial pressure build-up within pressure burst interval 72, no backplane gas is delivered to substrate support 20,

and therefore, valve 71 is closed (line F) . Furthermore, the RF

power to the inductive coil 42 is off (line D) as is the RF etch

power to substrate 14 (line E) . Referring again to line C, when the

processing chamber pressure rises to a set point, e.g. 30 mTorr,

designated by reference numeral 76, controller 59 turns on the RF

source 46 to provide power to inductor coil 42 (line D). An 800

watt power setting for RF source 46 has proven sufficient to ignite

a plasma in the apparatus 10 of the invention. Upon the ignition of

a plasma, which is indicated at the end of pressure burst interval

72, the throttle 76 to the vacuum pump 32 is opened, and the gas

flow rate of the MFC 60 is reduced (line B), thus, causing a drop in

the processing chamber pressure (line C). The gas flow through

the MFC 60 is maintained at a level to sustain the ignited plasma.

The power to coil 42 (line D) is adjusted from the 800 watt ignition level between upper and lower levels as shown to produce a

suitable plasma. Within the power-up interval 73, controller 59

turns on source 24 for etching substrate 14. As illustrated in line

E, the RF source 24 has an associated delay time to build up to the

desired output level, which may be around 50 volts. At the time of

plasma ignition, the backplane valve 71 is opened to provide backside heating gas to substrate support 20 to heat substrate 14

(line F) . The processing chamber valve 70 is alternately opened

and closed during the sputter etching process to maintain a desired

gas flow within the processing chamber. The plasma is sustained

and the substrate 1 4 is biased during the soft etch process interval

74. Upon reaching a predetermined etch time, the power to the

substrate (line E) is shut off during the power down interval 75.

The etch power to the substrate is shut off before the coil power

(line D) in order to determine the exact duration of the etch and to

prevent damage to the substrate which may occur if the substrate

remains biased when the plasma power is turned off. As illustrated

in lines D and E of Figure 3B, both the RF coil source and the RF

substrate source have predetermined delays at their outputs when switched off. At the end of the power-down interval 75, the mass

flow controller is closed (line B), the chamber valve is closed (line

G), and the isolation valve is closed (line H), thereby reducing the

gas pressure (line C) in the processing chamber 1 6.

As illustrated in line A, the opening of the vacuum

throttle 76 may be delayed if the gas flow and pressure within

chamber 1 6 is not sufficient to ignite a plasma. The delay is

illustrated by a dashed line in line A. Accordingly, the etch power to substrate 14 would also be delayed as illustrated by the dashed

line in line E of Figure 3B.

The processing apparatus of the present invention

provides a dense uniform plasma to etch substrate 14. The

apparatus is suitable for substrates utilizing small circuit devices

and features, and has a design which provides ease of service and

maintenance. The invention is capable of providing sufficiently

uniform and dense plasmas across large substrates at lower

pressures and low substrate biasing voltages.

In addition to the operation of pocket 40 and

contoured coil 42, the shape of the pocket and its depth of

extension into the processing space 34 may physically affect the

plasma to yield a more uniform etch. For example, a deep pocket

40 as is illustrated in Fig. 1 may physically displace the plasma

from above the center of substrate 14 to reduce the etch rate at

the center of the substrate which is often higher than the etch rate

at the substrate periphery. Therefore, the physical displacement

may yield a more uniform etch. Further detailed discussion of such

a plasma displacing plug is provided in Hieronymi et al., U. S.

Patent No. 5,391 ,231 , issued February 21 , 1 995, and is

incorporated herein in its entirety. The pockets 40 illustrated in the Figures are all

generally hollow and hold the contoured coil 42. Alternatively, the

pocket 40 may be filled with a dielectric material or other suitable

material (not shown) which will surround the contoured coil 42 in

pocket 40 and thereby embed the coil therein.

While the present invention has been illustrated by a

description of various embodiments and while these embodiments

have been described in considerable detail, it is not the intention of

the applicants to restrict or in any way limit the scope of the

appended claims to such detail. Additional advantages and

modifications will readily appear to those skilled in the art. The

invention in its broader aspects is therefore not limited to the

specific details, representative apparatus and method, and illustrative example shown and described. Accordingly, departures

may be made from such details without departing from the spirit or

scope of applicant's general inventive concept.

Claims

1 . A processing apparatus for sputter etching the surface

of a substrate with an ionized plasma, the apparatus comprising:

a processing chamber defining a processing space

and including a substrate support therein for supporting and

electrically biasing a substrate in said processing space;

a gas inlet for introducing sputtering gas into said

processing space proximate the substrate support; and

a plasma source coupled to an end of the processing

chamber to seal the chamber and create a plasma within the

chamber, the plasma source comprising: a dielectric plate having a non-conductive pocket

portion with a shaped inner surface and an outer surface, the

pocket portion physically extending into said processing space in

the chamber toward said substrate support;

an electrical energy source positioned outside of the

chamber and inside the pocket portion of said dielectric plate and

operable to efficiently couple energy through the pocket portion to

said sputtering gas for generating and sustaining a plasma of

ionized gas particles; the electrical energy source configured adjacent the

pocket portion outer surface for creating a high density uniform

plasma of ionized particles proximate a surface of a biased

substrate to bombard the surface thereof and produce a high

sputter etching rate uniformly across the substrate surface.

2. The processing apparatus of claim 1 wherein the

electrical energy source includes an inductive element positioned

and shaped in said pocket portion for inductively coupling energy to

the sputtering gas plasma.

3. The processing apparatus of claim 2 wherein the

inductive element includes a wire coil.

4. The processing apparatus of claim 3 wherein the coil

is contoured around the outer surface of the pocket portion.

5. The processing apparatus of claim 1 wherein the

electrical energy source includes an RF energy source.

6. The processing apparatus of claim 5 wherein the RF

energy source operates at a frequency approximately in the range

of 450 KHz to 1 5 MHz.

7. The processing apparatus of claim 5 wherein said

electrical energy source includes an RF tuner coupled to the RF

energy to reduce energy reflections back to the RF energy source

when energy is coupled to the plasma.

8. The processing apparatus of claim 1 further

comprising an RF energy source coupled to the substrate support

to bias a substrate on the support with RF energy.

9. The processing apparatus of claim 8 wherein the RF

energy source operates at a frequency approximately in the range

of 1 MHz to 1 5 MHz.

1 0. The processing apparatus of claim 1 wherein the

plasma source further comprises a metal electrostatic shield

positioned in the pocket portion for surrounding at least a portion

of the electrical energy source, the electrostatic shield operable to

absorb capacitive energy between the energy source and the

plasma to effectively reduce the capacitive coupling of energy from

the source to the plasma.

1 1 . The processing apparatus of claim 10 wherein the

shield is formed of a metal mesh.

1 2. The processing apparatus of claim 1 wherein the gas

inlet is located proximate the top of the chamber adjacent said

pocket portion and is angled to direct sputtering gas downwardly

into the processing space proximate the substrate support.

1 3. The processing apparatus of claim 1 further

comprising a gas ring above the substrate support and surrounding

the pocket portion for directing gas into the processing space from

around the pocket portion to produce a uniform plasma.

14. The processing apparatus of claim 1 further

comprising a shield positioned around the inside of the chamber for

capturing the sputter etched material and preventing the material

from contaminating the substrate surface.

1 5. The processing apparatus of claim 14 wherein the

shield is metal.

1 6. The processing apparatus of claim 1 further

comprising a magnetic ring surrounding the chamber for inducing a

magnetic field in the processing space proximate the substrate

support to magnetically confine the sputtering plasma and increase

the uniformity and density of the plasma to increase the sputter

etch rate at the substrate surface.

1 7. The processing apparatus of claim 1 wherein the

dimensions of the non-conductive pocket portion and the

configuration of the energy source adjacent the pocket portion are

variable for selectively varying the plasma uniformity and density

across the substrate surface to selectively vary the sputter etch

rate across the surface.

1 8. A processing apparatus for sputter etching the surface

of a substrate with an ionized plasma, the apparatus comprising:

a processing chamber defining a processing space

and including a substrate support therein for supporting and

electrically biasing a substrate in said processing space;

a gas inlet for introducing sputtering gas into said

space proximate the substrate support; and

a plasma source coupled to an end of the chamber to

seal the chamber and create a plasma within the chamber, the

plasma source comprising:

a dielectric plate having a non-conductive pocket

portion with a shaped inner surface and an outer surface, the

pocket portion physically extending into said processing space in

the chamber toward said substrate support;

an inductive coil positioned outside the chamber and

inside the pocket portion of said dielectric plate for efficiently

inductively coupling energy through the pocket portion to said sputtering gas for generating and sustaining a plasma of ionized

gas particles; the inductive coil shaped adjacent said pocket portion

outer surface for creating a high density uniform plasma of ionized

particles proximate a surface of a biased substrate to bombard the

surface thereof and produce a high sputter etching rate uniformly

across the substrate surface.

1 9. The processing apparatus of claim 1 8 wherein said

inductive coil is wound concentrically around the outer surface of

the non-conductive pocket portion.

20. The processing apparatus of claim 1 8 wherein the

plasma source further comprises a metal electrostatic shield

positioned in the pocket portion, the shield surrounding at least a portion of the inductive coil and operable to absorb capacitive

energy between the inductive coil and the plasma to effectively

reduce the capacitive coupling of energy from the inductive coil to

the plasma.

21 . The processing apparatus of claim 1 8 further

comprising a shield positioned around the inside of the chamber for

capturing the sputter etched material and preventing the material

from contaminating the substrate surface.

22. A plasma source for creating a plasma inside of a

processing chamber to sputter etch a biased substrate inside the

chamber, the plasma source comprising:

a dielectric plate coupled to an end of the chamber,

the dielectric plate including a non-conductive pocket portion with a

shaped inner surface and an outer surface, the pocket portion

physically extending into said processing chamber toward a biased

substrate in the chamber;

an electrical energy source positioned outside the

chamber and inside the pocket portion of said dielectric plate and

operable to efficiently couple energy to sputtering gas inside the

chamber for generating and sustaining a plasma of ionized gas

particles;

the electrical energy source configured adjacent the

pocket portion outer surface for creating a high density uniform

plasma of ionized particles proximate a surface of a biased

substrate to bombard the surface thereof and produce a high

sputter etching rate uniformly across the substrate surface.

23. The plasma source of claim 22 wherein the electrical

energy source includes an inductive element positioned and shaped

in said pocket portion for inductively coupling energy to the sputtering gas plasma.

24. The plasma source of claim 23 wherein the inductive

element includes a wire coil.

25. The plasma source of claim 24 wherein the coil is

contoured around the outer surface of the pocket portion.

26. The plasma source of claim 22 further comprising a

metal electrostatic shield positioned in the pocket portion for surrounding at least a portion of the electrical energy source, the

electrostatic shield operable to absorb capacitive energy between

the energy source and the plasma to effectively reduce the

capacitive coupling of energy from the source to the plasma.

27. The plasma source of claim 26 wherein the shield is

formed of metal mesh.

28. The plasma source of claim 22 further comprising a gas ring surrounding the pocket portion to direct gas into the

processing space from around the pocket portion to produce a

uniform plasma.

29. The plasma source of claim 22 further comprising a

magnetic ring surrounding the chamber for inducing a magnetic

field proximate a substrate to magnetically confine the sputtering

plasma and increase the uniformity and density of the plasma to

increase the sputter etch rate at the substrate surface.

30. A method of sputter etching the surface of a substrate with an ionized plasma, the method comprising:

electrically biasing a substrate inside of a processing chamber;

introducing sputtering gas into said processing

chamber proximate the substrate;

coupling, to an end of the processing chamber, a

dielectric plate having a non-conductive pocket portion with a

shaped inner surface and an outer surface, the pocket portion

physically extending into said processing chamber proximate said

substrate;

positioning an electrical energy source inside the

pocket portion of said dielectric plate and coupling energy to said sputtering gas through the pocket portion to generate and sustain a

plasma of ionized gas particles;

configuring the electrical energy source adjacent the

pocket portion outer surface for creating a high density uniform

plasma of ionized particles proximate a surface of the biased

substrate to bombard the surface thereof and produce a high

sputter etching rate uniformly across the substrate surface. 31 . The method of claim 30 further comprising positioning

and shaping an inductive coil around the outer surface of said

pocket portion for inductively coupling energy to the sputtering gas

plasma.

32. The method of claim 30 wherein the electrical energy

source includes an RF energy source.

33. The processing apparatus of claim 30 further

comprising placing a metal electrostatic shield in the pocket portion

to surround a portion of the electrical energy source, the

electrostatic shield operable to absorb capacitive energy between

the energy source and the plasma to effectively reduce the

capacitive coupling of energy from the source to the plasma.

34. The method of claim 30 further comprising introducing

sputtering gas into the processing chamber from a gas ring above

the substrate and surrounding the pocket portion to produce a

uniform plasma. 35. The method of claim 30 further comprising placing a

metal shield around the inside of the chamber and capturing the

sputter etched material with the shield to prevent the material from contaminating the substrate surface.

36. The method of claim 30 further comprising

surrounding the outside of the chamber with a magnetic ring and

inducing a magnetic field in the processing space proximate the

substrate support to magnetically confine the sputtering plasma

and increase the uniformity and density of the plasma to increase

the sputter etch rate at the substrate surface.

AMENDED CLAIMS

[received by the International Bureau on 17 June 1996 ( 17.06.96) ; original claims 2 , 4 , 17 , 18-21 , 23 , 25 and 31 cancel led ; original claims 1 , 3 , 10 , 22 , 24 , 26 , 28 , 30 and 33 amended ; remaining claims unchanged ( 1 1 pages ) ]

1 . A processing apparatus for sputter etching the surface of a

substrate with an ionized plasma, the apparatus comprising:

a processing chamber defining a processing space and

including a substrate support therein for supporting and electrically

biasing a substrate in said processing space;

a gas inlet for introducing sputtering gas into said processing

space proximate the substrate support; and

a plasma source coupled to an end of the processing chamber

to seal the chamber and create a plasma within the chamber, the

plasma source comprising:

a dielectric plate having a non-conductive pocket portion with a

convexly-curved inner surface and a concavely-curved outer surface,

the pocket portion physically extending into said processing space in

the chamber toward said substrate support so that the concavely-

curved outer surface curves outwardly in the direction of said

substrate support;

an inductive coil positioned outside of the chamber and inside

the pocket portion of said dielectric plate, the inductive coil being

contoured inside of said pocket portion to have a generally concave

shape in the direction of the substrate support coinciding with the

concavely-curved outer pocket surface of the pocket portion, the

concavely shaped coil operable to efficiently inductively couple energy

through the pocket portion to said sputtering gas for generating and sustaining a plasma of ionized gas particles;

the concavely shaped coil and coinciding concavely-curved

outer pocket surface creating a high density uniform plasma of ionized

particles proximate a surface of a biased substrate to bombard the

surface thereof and produce a high sputter etching rate uniformly across the substrate surface.

2. CANCEL

3. The processing apparatus of claim 1 wherein the concavely shaped inductive coil is formed of wire.

4. CANCEL

5. The processing apparatus of claim 1 wherein the electrical

energy source includes an RF energy source.

6. The processing apparatus of claim 5 wherein the RF energy

source operates at a frequency approximately in the range of 450 KHz

to 1 5 MHz.

7. The processing apparatus of claim 5 wherein said electrical energy source includes an RF tuner coupled to the RF energy to reduce

energy reflections back to the RF energy source when energy is

coupled to the plasma.

8. The processing apparatus of claim 1 further comprising an RF

energy source coupled to the substrate support to bias a substrate on

the support with RF energy. 9. The processing apparatus of claim 8 wherein the RF energy

source operates at a frequency approximately in the range of 1 MHz to

1 5 MHz.

1 0. The processing apparatus of claim 1 wherein the plasma source

further comprises a metal electrostatic shield positioned in the pocket

portion for surrounding at least a portion of the coil, the electrostatic

shield operable to absorb capacitive energy between the coil and the

plasma to effectively reduce the capacitive coupling of energy from

the coil to the plasma.

1 1 . The processing apparatus of claim 10 wherein the shield is

formed of a metal mesh.

1 2. The processing apparatus of claim 1 wherein the gas inlet is

located proximate the top of the chamber adjacent said pocket portion

and is angled to direct sputtering gas downwardly into the processing

space proximate the substrate support.

1 3. The processing apparatus of claim 1 further comprising a gas

ring above the substrate support and surrounding the pocket portion

for directing gas into the processing space from around the pocket

portion to produce a uniform plasma. 14. The processing apparatus of claim 1 further comprising a shield

positioned around the inside of the chamber for capturing the sputter

etched material and preventing the material from contaminating the

substrate surface.

1 5. The processing apparatus of claim 1 4 wherein the shield is

metal.

1 6. The processing apparatus of claim 1 further comprising a

magnetic ring surrounding the chamber for inducing a magnetic field in

the processing space proximate the substrate support to magnetically

confine the sputtering plasma and increase the uniformity and density

of the plasma to increase the sputter etch rate at the substrate

surface.

1 7. CANCEL

CANCEL CLAIMS 1 8-21

22. A plasma source for creating a plasma inside of a processing

chamber to sputter etch a biased substrate inside the chamber, the

plasma source comprising:

a dielectric plate coupled to an end of the chamber, the

dielectric plate including a non-conductive pocket portion with a

convexly-curved inner surface and a concavely-curved outer surface,

the pocket portion physically extending into said processing chamber

toward a biased substrate in the chamber so that the concavely-

curved outer surface curves outwardly in the direction of the

substrate;

an inductive coil positioned outside the chamber and inside the pocket portion of said dielectric plate, the inductive coil being

contoured inside of said pocket portion along the convexly-curved

inner surface to have a generally concave shape in the direction of the

substrate coinciding with the concavely-curved outer surface of the

pocket, the concavely shaped coil operable to efficiently inductively

couple energy to sputtering gas inside the chamber for generating and

sustaining a plasma of ionized gas particles;

the concavely shaped coil and coinciding concavely-curved outer pocket surface creating a high density uniform plasma of ionized

particles proximate a surface of a biased substrate to bombard the

surface thereof and produce a high sputter etching rate uniformly

across the substrate surface. 23. CANCEL

24. The plasma source of claim 23 wherein concavely shaped

inductive coil is formed of wire.

25. CANCEL

26. The plasma source of claim 22 further comprising a metal

electrostatic shield positioned in the pocket portion for surrounding at

least a portion of the inductive coil, the electrostatic shield operable

to absorb capacitive energy between the coil and the plasma to

effectively reduce the capacitive coupling of energy from the coil to

the plasma.

27. The plasma source of claim 26 wherein the shield is formed of

metal mesh.

28. The plasma source of claim 22 further comprising a gas ring

surrounding the pocket portion to direct gas into the processing

chamber from around the pocket portion to produce a uniform plasma. 29. The plasma source of claim 22 further comprising a magnetic

ring surrounding the chamber for inducing a magnetic field proximate a

substrate to magnetically confine the sputtering plasma and increase

the uniformity and density of the plasma to increase the sputter etch

rate at the substrate surface.

30. A method of sputter etching the surface of a substrate with an

ionized plasma, the method comprising:

electrically biasing a substrate inside of a processing chamber; introducing sputtering gas into said processing chamber

proximate the substrate;

coupling, to an end of the processing chamber, a dielectric plate

having a non-conductive pocket portion with a convexly-curved inner

surface and a concavely-curved outer surface, the pocket portion

physically extending into said processing chamber proximate said

substrate;

positioning the substrate in the chamber such that the pocket

portion concavely-curved outer surface curves outwardly in the

direction of said substrate

positioning an inductive coil inside the pocket portion of said

dielectric plate and inductively coupling energy to said sputtering gas

through the pocket portion to generate and sustain a plasma of ionized

gas particles;

contouring the inductive coil inside of the pocket portion and

forming a coil with a generally concave shape curving outwardly in the

direction of the substrate to coincide with the concavely-curved outer

surface for creating a high density uniform plasma of ionized particles

proximate a surface of the biased substrate to bombard the surface

thereof and produce a high sputter etching rate uniformly across the

substrate surface.

31 . CANCEL

32. The method of claim 30 wherein the electrical energy source

includes an RF energy source.

33. The processing apparatus of claim 30 further comprising placing

a metal electrostatic shield in the pocket portion to surround a portion

of the coil, the electrostatic shield operable to absorb capacitive

energy between the coil and the plasma to effectively reduce the

capacitive coupling of energy from the coil to the plasma.

34. The method of claim 30 further comprising introducing

sputtering gas into the processing chamber from a gas ring above the

substrate and surrounding the pocket portion to produce a uniform

plasma.

35. The method of claim 30 further comprising placing a metal

shield around the inside of the chamber and capturing the sputter

etched material with the shield to prevent the material from

contaminating the substrate surface.

36. The method of claim 30 further comprising surrounding the

outside of the chamber with a magnetic ring and inducing a magnetic

field in the processing space proximate the substrate support to

magnetically confine the sputtering plasma and increase the uniformity

and density of the plasma to increase the sputter etch rate at the

substrate surface.