DE102013113687A1 - coating system - Google Patents

Abstract

Coating systems, especially in semiconductor technology, usually coat only one side of a substrate. This leads to strains and sometimes strong wafer curvatures in heterosystems. The present invention relates to a coating system which is characterized by a simultaneous or alternating double-sided coating of a substrate during a coating process, which takes place between the introduction into the coating apparatus and the application of the coated substrate. The system enables substrate coating on both sides or on all sides, enabling extremely flat wafers and the use of both sides for components.

Description

The invention relates to a coating system for semiconductor technology, as well as a method for coating.

Substrates for functional applications are usually coated on one side with functional layers in coating systems. This is the case in particular for compound semiconductors. During growth on heterosubstrates, strain usually occurs, which complicates the processing due to the curvature of the substrate. It has also been observed that, depending on the type of substrate, in particular in the case of Si substrates and here in the case of high-purity float zone substrates, moderate strain, plastic deformation can already be observed in comparison to growth on other substrates. This makes such coated substrates usually useless, since the plastic deformation leads to irregular and very strong, non-recovering deformations.

Against this background, the object of the present invention is to overcome the disadvantages mentioned.

This object is now achieved by a method according to claim 1, a semiconductor device according to claim 7 and a coating system according to claim 8.

A method is proposed for coating substrates for semiconductor components by means of a coating system with a coating chamber, wherein a simultaneous or alternating double-sided coating of a substrate during a coating process takes place between the introduction of the substrate into the coating chamber and the application of the coated substrate.

The coating process by means of respective starting materials can take place continuously or interrupted or with alternating supply of the respective starting materials, as is usual, for example, in atomic layer deposition.

With the present invention, components are provided which have a compound semiconductor on both sides of the substrate.

With this coating method, a substrate can be provided, which is flat after and ideally also during the process and in which the plastic deformation occurs clearly delayed compared to the one-sided coating of substrates. Significantly delayed means at least 1.5-fold tension per side or at constant tension, at 1.5-fold layer thickness.

Preferably, the coating is applied simultaneously on both sides. However, it is also possible, depending on the coating system, to apply this coating alternately, with the substrate being turned in one embodiment. In this case, each deposited individual layers should not exceed 1000 nm in one-sided deposition before the substrate is turned again. Especially at high tension z. B. on silicon substrates, this value must be exceeded in order to prevent plastic deformation by the asymmetry of the strain, so a one-sided significantly stronger force on the substrate.

Further advantages of a double-sided coating are, for. As with thin-film LEDs, a doubled yield per wafer, since LEDs can be made on each side. Also, in systems where plastic deformation occurs under severe stress, thicker or more stressed layers may be deposited, and there are devices where double-sided coating can provide performance benefits.

In a preferred embodiment, a coating chamber is provided which is heated on at least two opposing walls and between which walls a substrate is attached for coating so that a gas stream containing the starting materials to be coated can flow around both sides of the substrate. In order to prevent excessive cooling of the substrate by the gas flow, the entire chamber may be heated and only the gas inlets of heat-sensitive raw materials cooled, thus preventing early decomposition and reaction of these substances is prevented.

Even in conventional systems, such a coating can take place after conversion of the sample holder.

A further embodiment of the invention provides that the substrate can also be coated in each case only from one side, wherein a coating chamber is provided with sources for the substrate (s) to be coated, for the purpose of a coating which takes place in synchronism over the deposition time in a synchronized manner Substrate for this purpose by a device in the coating chamber or this can be rotated directly upstream.

In this case, one side of the substrate may be coated a few nanometers thicker than the other side. The device can also be arranged outside the actual coating chamber, but in a region with defined conditions, ie defined gas to avoid contamination.

A double-sided coating can be carried out particularly advantageously in a coating chamber with sources for the substance (s) to be coated, respectively facing and facing a first or second surface of a substrate to be coated, and with a coating which is synchronous or averaged over the deposition time synchronously ,

According to the method, in most systems, in order to obtain a homogeneous thickness and composition distribution over the substrate, the rotation of the substrate is about the vertical axis.

Not necessarily systems at working pressures in the range of a few mbar to over 1 bar are necessary to achieve a double-sided coating.

In addition to coating in or out of a gas stream, the coating chamber may also have a vacuum in which there is a heated substrate that can be coated from both sides with a controllable gas stream containing at least the starting materials of the layer.

The method makes it possible to realize advantageous semiconductor components in which the production requires a substrate coated on both sides.

As an example of advantageous components here components based on GaN are called. These are, among other things, transistors. Thus, high-voltage components with improved breakdown resistance can be achieved by the bilateral GaN layer. At present, when grounding the substrate, as happens in conventional device structures, a reduction in breakdown voltage due to breakdown across the Si substrate is observed [ A. Dadgar, et al., Physica Status Solidi C 8, 1503 (2011) ].

With an insulating layer this can be doubled. When two identical layers are grown on both sides of the substrate, this layer can be used as an additional component or, analogously to the LEDs listed below, the components can be doubled in half by separating the substrate or the substrate to double the yield per wafer.

If small variations in the layer deposition on both sides are possible, you can close the device such. B. transistors and so on one side n-channel and realize on the other p-channel devices or depletion and enhancement type transistors.

When using polar substrates such as c-axis oriented GaN, a p-channel as well as an n-channel device on a substrate can easily be realized with double-sided coating, as then automatically, with identical layer sequence, a p- and an n-channel each formed on a substrate side.

Light-emitting diodes can also be used on separable substrates such. B. SOI are deposited. By gluing the functional layers to new supports, which is improved by the planarity achieved in double-sided coating, and the dissolution of the oxide layer or mechanical separation along it, so two wafers are grown, albeit on only one substrate. In principle, however, such a separation of the functional layers from each other without the use of an SOI substrate is possible if the substrate can be separated into two parts by etching, laser sawing or splitting, mechanical sawing or breaking.

In addition, the layers may be separated by sticking or bonding to new supports and then partially or completely removing the substrate used in the growth process. This can be achieved by different methods such. As wet-chemical etching or a laser or mechanical separation process followed by a wet-chemical removal of the substrate residues.

For three-dimensionally shaped objects such. B. coil springs, which are to be coated with functional layers allows the process, the all-round coating z. With c-axis oriented AlN, each aligned perpendicular to the surface normal to the c-axis.

An embodiment of the invention provides a coating system for producing semiconductor components with a coating on both sides, comprising at least:
a coating chamber having at least two opposing walls for simultaneously or alternately coating both sides of a substrate during a coating operation that occurs between the introduction and application of the substrate into the coating chamber.

In a further embodiment, a coating system is provided, in which the coating chamber can be heated on at least two opposite walls and between which a substrate for coating can be fastened and the substrate by means of a gas stream containing the starting materials to be coated, can be flowed around on both sides.

In a preferred embodiment of the invention, a coating system is provided in which the coating chamber has sources for the substance or substances to be coated, wherein the substrate is rotatably mounted by means of a device in the coating chamber or directly in front of or directly adjacent thereto. This upstream region is preferably heated in order to minimize thermally induced tensions and, if necessary, also to allow a stabilizing gas atmosphere.

It does not necessarily have to be arranged in front of the chamber, but can also be arranged after a lock laterally from the reactor or above or below the reactor, but must be located in the same plant to z. As caused by impurities disturbances of the surface or thermally induced tensions.

According to a further embodiment of the invention, the coating system is characterized in that the coating chamber has feeds for or onto the substrate to be coated substances, which are respectively arranged opposite and facing a first and second surface of a substrate to be coated and the one synchronous or averaged effect a synchronous deposition over the deposition time.

The substances can be fed into the coating chamber independently of each other, so that when z. B. 2 starting materials are required, first only the first starting material is passed into the chamber, then the supply line is stopped, and then the second starting material is passed into the chamber, is stopped again and this cycle is then repeated. Between the introduction of the various substances can still be switched to a rinsing cycle.

However, the introduction of the starting materials can also be designed to overlap in time, or the starting materials can be conducted together into the coating chamber. So it is possible to realize only atomic layer deposition, or a continuous growth such. B. in the MOVPE, or a combination of both methods.

For the design of the coating system, a device with a gas guide is preferred, which flows around the substrate on both sides. This can be done both horizontally and subsequently in the 1 - 8th , and 11 - 15 shown as well as in the vertical direction of the gas flow, according to the 9 and 10 and horizontal direction according to the 1 - 11 and 15 and vertical reactor assembly according to the 12 - 14 respectively.

The heating takes place on both sides of the coating chamber, preferably by a heatable wall z. B. inductively, or heated with resistance or lamp heating. Care must be taken to ensure that the gas used does not strongly cool the substrate and thus, especially in the edge region, leads to too low a temperature and thus inhomogeneities in the composition, layer thickness or bracing.

Also advantageous are several gas inlets that make the gas distribution or the starting materials uniform on both sides and thus provide a homogeneous coating.

There are several possibilities for the substrate holder. So pins are possible in a holding plate, which engage the edge of the substrate. Embodiments are described below 1 shown. The number and arrangement is virtually arbitrary, are advantageous for three holders, ideally offset by 120 °. Two holders must be as in 2 shown designed to prevent tilting of the substrate.

Also possible is the bracket on the edge as in below 3 shown, which has a greater separation in the upper and lower gas flow and thus less influence on both gas flows result. This makes it easier to deposit different layers on both sides, and these are ideally designed so that the overall stress and thus the substrate deflection remains low. The gas supply must be in the 1 - 3 not necessarily done by the side, but can also, as in the 9 and 10 shown to be executed vertically on the substrate.

Applying the method to a single-sided coating using the substrate to achieve a two-sided coating, so conventional system configurations are possible, but advantageously one that allows turning at high temperatures, ideally at deposition temperature. Particularly suitable for this purpose are turning devices made of molybdenum or another refractory metal, which grip the substrate at the edge and, if possible even in a hot zone, turn.

It is advantageous not to lay the substrate on a susceptor over the entire surface, but only hang on the edge to a particle contamination to avoid the previous surface, as shown below 15 shown.

The following is a description of the figures and some of the possible embodiments of the invention.

Show it:

1 and 2 FIG. 2 schematically shows various arrangements of a substrate on a rotating holder, FIG.

3 schematically the substrate arrangement 1 in a reactor,

4 and 5 FIG. 2 schematically shows an alternative type of support of the substrates, FIG.

6 schematically the installation of a system, as in 4 and 5 shown in a reactor,

7 : schematically a top view of the in 6 shown system,

8th schematically a cross section through the reactor from the 6 and 7 .

9 and 10 in each case schematically the arrangement of the substrate in a showerhead reactor,

11 FIG. 2 schematically shows a horizontal reactor type with separate gas inlet, FIG.

12 and 13 FIG. 1 schematically shows a reactor in vertical design with gas inlet below (FIG. 12 ) and above ( 13 )

14 schematically a vertical arrangement for coating a plurality of substrates in a chamber and

15 FIG. 2 schematically shows an arrangement with rotating support of the substrate at the edge. FIG.

1 shows a substrate 100 on a rotating holder 101 on it in the gas stream with holders 102 is elevated. Here, the height is ideal in the middle but may differ, since the growth rates above all on the composition of the gas flow above and below the substrate 100 are dependent. The arrows indicate the approximate direction of the gas flow but it can also be a vertical gas supply.

Analogous to this is in 2 a substrate 200 on a rotating holder 201 with only two holders 202 supported. Here is also an embodiment in which no holes in the substrate are needed. Also, the holder can be led away more laterally, so that the vortex behind it, the growth on the substrate in the holder area not or only very little disturb. Such vortices are significantly minimized or hardly interfere with the growth on the substrate when they are carried by the gas flow in an area outside the substrate with a vertical gas supply.

In 3 the situation is over 1 in a reactor shown with the substrate 300 the holders 301 and the bottom one 302 and upper 303 Reactor walls, which are ideally heated. The sidewalls are also preferably heated, this is less important as long as they are far from the substrate.

As an alternative to heating the walls, the substrate can also be heated directly by an infrared or lamp heater or, in the case of highly conductive substrates, by means of high-frequency induction heating. The heating can also be combined, in particular to reduce cooling effects of the gas on the substrate, a heating of the walls and at the same time the substrate takes place, either with IR radiators or high frequency heaters and appropriate choice of materials of the walls and the substrate.

In 3 For simplicity, the rotatable sample holder has not been drawn, but only the substrate with holder.

The 4 and 5 show an alternative bracket type. Here is the substrate 400 respectively. 500 from or in a ring 401 respectively. 501 supported. This is powered by magnetic or mechanical drive in two 402 or three 502 or more holders rotated. It can only grab a large holder to a half-space of the retaining ring to drive this.

Alternatively, a gas stream can put the ring in rotation on a gas cushion. For this purpose, it should be designed with corresponding grooves, which generate a rotational movement, and minimize an influx of the rotational gas onto the substrate by suitable design measures.

It is even possible that only the substrate is rotated by a gas stream in rotation, and that can be dispensed with the ring for the support of the substrate.

With horizontal gas inlet, the gas can escape in the rear area, with the Showerheadgaseinlässen side of the ring. In an embodiment with a so-called Showerheadgaseinlass above and below the substrate and the Gas inlets rotate or is a rotation of the substrate but also the gas inlet is not mandatory.

The installation of a system as in 4 and 5 shown in a reactor is in 6 shown. Here is the substrate 600 in the retaining ring 601 , The drive is not shown here, the surrounding upper 603 and lower 602 Reactor walls are ideally heated.

This is in 7 the top view with substrate 700 , Retaining ring 701 , Drive units for rotation 702 and the lateral reactor walls 703 shown. These can but do not have to be actively heated.

8th shows a cross section through the reactor with the substrate 800 , the substrate holder 801 , the drive units for rotation 805 the lateral reactor walls 804 and the bottom one 802 and upper 803 Reactor wall. 806 indicates the arrows of the gas flow, ie here you look at the gas flow.

If small variations in the layer deposition on both sides are possible, one can close the completion of the semiconductor device such. B. in transistors and so on one side n-channel and realize on the other p-channel devices or depletion and enhancement type transistors, as in the following 9 - 13 is shown.

In 9 By analogy, a showerhead reactor is shown in which the gas is passed through inlets. 903 and below 902 of the substrate 900 , held in 901 , is initiated. The arrows indicate schematically the gas flow.

All reactors do not have to be horizontal. A horizontal design can have disadvantages in terms of homogeneity, as here hot rising gases affect the composition of the reactants on the substrate surface even with identical composition at the gas inlet.

In 10 is a vertical showerhead reactor shown with gas inlets 1002 and 1003 , the substrate 1000 in the holder 1001 , By rotating the substrate inhomogeneity can be avoided by varying degrees up and down gas flowing. To store the substrate and to set in rotation, a storage on a gas cushion offers.

The substrate can be held in position by the same gas stream and rotated at the same time. Since no retaining ring is present, the substrate is ideally surrounded by an undisturbed flow of coating gases, which is advantageous for the homogeneity of the coating. However, this requires circular wafers without flat, so that the marking of the crystal orientation for the subsequent further processing of the substrate must be done in other ways.

11 shows a horizontal reactor type with separate gas inlet for the upper area 1103 divided into two inlets 1105 and 1106 if necessary to separate different types of gas, similar to the bottom section 1102 with separate lower gas inlets 1107 and 1108 , a separating plate 1104 , the substrate 1100 , the retaining ring 1101 as well as lower and upper reactor wall.

The plate 1104 does not necessarily close gas-tight, but you can constructively prevent a strong gas exchange by the gap is very narrow or is provided with a small gas labyrinth, ie z. B. a splitting of 1104 the top and bottom 1101 something overlaps ..

12 shows analogously such a vertical reactor with gas inlet below, which promotes the gas transport by the heating of the gases introduced, and in 13 with gas inlet on top, which can lead to greater turbulence by the heating of the gas stream and then the gas stream opposite convection.

In particular, in a vertical embodiment, several substrates can be coated in a chamber as in 14 shown schematically. Although this is feasible for horizontal design, it is harder to control in the process as a result of gas convection. These substrates can also be through rods like in 1 be held, then the rods would connect the substrates and open into brackets on the edge. In general, however, the holding plates can be connected to rods, ie there need not necessarily be small notches on the edge or holes in the substrates to support them. The holding plates would ideally consist of two parts in a vertical structure between which the substrates are clamped at the edge.

15 shows an embodiment in the case of growing with Wafer turning. Here lies the substrate 1500 on an ideally rotating mount 1501 on the edge. The gas flows at least largely over the substrate, so that if there is minimal growth on the bottom. The reactor is going up 1503 and below 1502 and limited by lateral, not shown in the figure walls. In this design, the substrate must be turned several times during the process, which can be done fully automatically by skillful design execution.

Even conventional systems can be used after a modification of the sample holder for such a coating.

Almost all versions shown can be combined with each other and can be implemented in all systems of gas phase epitaxy. In principle, a design in the MBE is conceivable, this is similar to the gas flow of a showerhead, except that here the chamber is shaped differently and the showerhead must be replaced by the individual sources, each on each side of the substrate.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• A. Dadgar, et al., Physica Status Solidi C 8, 1503 (2011) [0020]

Claims (11)

 A method for coating substrates for semiconductor devices by means of a coating system, comprising a coating chamber, characterized by a simultaneous or alternating double-sided coating of the substrate during a coating operation, which takes place between the introduction of the substrate into the coating chamber and the application of the coated substrate.  A method according to claim 1, characterized in that the coating chamber is heated on at least two opposite walls and between which a substrate is attached for coating, so that a gas stream containing the starting materials to be coated, can flow around both sides of the substrate.  A method according to claim 1, characterized in that the coating chamber is provided with sources for the substrate (s) to be coated, wherein the coating is averaged synchronously over the deposition time and wherein the substrate can be rotated by a device in the coating chamber or directly upstream thereof. Method according to claim 1, characterized in that a coating chamber with Sources of the substrate (s) to be coated each opposite and facing a first or second surface of a substrate to be coated is provided and a coating which is synchronous or averaged synchronously over the deposition time.  Method according to at least one of the preceding claims, characterized by the rotation of the substrate about the axis vertical to the substrate surface.  A method according to claim 1, comprising a vacuum deposition chamber containing a heated substrate which can be coated from both sides with a controllable gas stream containing at least the starting materials of the layer.  Semiconductor component, characterized by the production from a substrate coated on both sides.  Coating system for the production of semiconductor devices with a double-sided coating, comprise at least: a coating chamber having at least two opposing walls for simultaneously or alternately coating both sides of a substrate during a coating operation that occurs between the introduction and deployment of the substrate into the growth chamber.  Coating system according to claim 8, characterized in that the coating chamber is heatable on at least two opposite walls and between which a substrate for coating can be fastened and the substrate by means of a gas stream containing the starting materials to be coated, is flowed around on both sides.  Coating system according to Claim 8, characterized in that the coating chamber has sources for the substance (s) to be coated, wherein the substrate is rotatably supported directly adjacent by means of a device in the coating chamber or the coating chamber. Coating system according to claim 8, characterized in that the coating chamber has sources for the substance or substances to be coated, which are respectively arranged opposite and facing a first and second surface of a substrate to be coated and which cause a synchronous or averaged deposition over the deposition time.

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