Patent Application
20060118043
International Patent Document WO98/58099 is attached to this specification as a description of the process.
The present invention relates to a process for producing parts as electronic, opto-electronic, optical or micromechanical components or as intermediate products therefor by using at least one plasma-enhanced treatment step, in which reactive gas or reactive gas mixture admitted to a process space is activated by means of a low-energy plasma discharge with ion energy E on the surface of the part of
0 eV<E<15 eV
Furthermore, the invention relates to a process for producing a virtual substrate or a component thereof, preferably on a silicon germanium base, comprising at least one cleaning step, according to the preamble of Claim 28. In addition, the invention relates to vacuum treatment systems.
The present invention basically relates to the production of parts for which the same demands are to be made as during the coating of parts with an epitaxial layer.
From International Patent Document WO98/58099 (enclosed) by the same applicant, processes as well as systems of the initially mentioned type are known. As a plasma-enhanced treatment step, in which reactive gas or reactive gas mixture admitted to a process space is activated by means of a low-energy plasma discharge with ions of the ion energy E on the surface of the part of
0 eV<E<15 eV,
is described in detail and only the coating of a workpiece of a quality sufficient for the epitaxy is described and claimed there. The plasma generated by the low-energy plasma discharge is essentially composed of electrons, single and multiple charged ions and neutral particles (atoms, dissociated molecules) as well as excited but non-ionized neutral particles. The energy range
0 eV<E<15 eV
of the single ionized ions is characteristic of the plasma described herein. 15 eV represents the so-called sputtering threshold, above which, when the ions act upon the substrate, damage may occur there. Even up to 100 eV, electrons contribute essentially only to the heating of the substrate. It is also known that, particularly in the case of the DC low voltage plasma generating arrangement particularly preferred in this case—as will be explained in the following the above-mentioned energy range of the single-charged ions simultaneously limits in the upward direction the energy range of the neutral particles existing in the plasma as well as excited neutral particles. The reason is that the neutral particles obtain their significant energy contribution by impacts with the ions.
Also, a vacuum treatment system for the above-mentioned coating is explained in detail in International Patent Document WO98/58099 and has a vacuum chamber, a workpiece carrier in the vacuum chamber, a plasma generating arrangement for generating a plasma in the chamber as well as a gas inlet arrangement in the chamber which is connected with a gas tank arrangement with at least one reactive gas. The plasma generating arrangement is described specifically as a low-voltage plasma generating arrangement: A cathode chamber communicates by way of a diaphragm with the process space. A hot cathode is mounted in the cathode chamber; an anode arrangement is present in the process space. Having a physically downward orientation, the workpiece carrier is arranged in an electrically insulated manner.
The principle of this low-voltage plasma generating arrangement is far preferred for the processes described herein over also known other plasma generating processes (such as microwave plasma), because it is capable of obtaining the above-mentioned energy characteristics in a preferred manner.
Thus, on the one hand, the present invention is based on processes and a system of this type; on the other hand, among others, the process described in International Patent Document WO98/58099 is to be implemented also according the present application, although—as will be explained in the following—while meeting additional criteria according to the object of the present invention.
The reason is that it is an object of the present invention to provide a process and a system of the above-mentioned type whose industrial suitability is significantly increased with respect to economic criteria, particularly with respect to higher up-times and higher troughput.
During the required high up-times, the high purity of the system has to be ensured for the above-mentioned processes. In addition, an optimal integrability of the process steps on the one hand, and of the system, on the other hand/or automated production should be achieved.
With respect to the process of the initially mentioned type, this object is achieved in that the process atmosphere during the plasma-enhanced treatment step is separated from the interior wall of a vacuum recipient exposed to the environment. The basic recognition is in this case that a functional separation, on the one hand, of structures which ensure the required vacuum-related pressure condition with respect to the ambient pressure and, on the other hand, of structures which are directly exposed to the treatment process will achieve the above-mentioned object.
According to International Patent Document WO98/58099, the interior surface of the vacuum chamber, normally made of stainless steel or Inox, is exposed directly to the process atmosphere. During the plasma-enhanced treatment step, specifically during the coating of workpiece or part by means of the low-energy plasma discharge, the vacuum chamber wall and thus the interior surface will heat up. Because of various effects, such as the absorption behavior of the interior surface during the preceding process exposures, if used in industrial manufacturing, this results in an intolerable contamination of the treatment step process atmosphere or in the formation of intolerable partial background gas pressures. Background gas in a process atmosphere in this case are those gas fractions which originate neither from the plasma discharge working gas, such as argon, nor from the admitted reactive gas or reactive gas mixture, nor from their gaseous reaction products. As a result of the approach according to the invention, it will now be possible to minimize the influence upon the process by the vacuum recipient wall.
The process according to the invention is used in a preferred manner (a) for coating the part or (b) for changing the material composition of the part to a defined penetration depth, or (c) for etching the surface of the part, particularly for etching of structure. In all mentioned cases, it is absolutely necessary to maintain process conditions required for the growth of epitaxial layers, within the scope of the production processes endeavored according to the invention. As a result of the change of the material composition according to the invention mentioned in (b), this addresses the implantation of material into a given target material.
Furthermore, a cleaning step suggested as a plasma-enhanced treatment step carried out according to the invention, or a cleaning step is suggested in addition to a plasma-enhanced treatment step according to the invention.
In a preferred embodiment of the process of the invention, a virtual substrate is produced. A virtual substrate is a semiconductor wafer which, in contrast to a wafer consisting of a generally monocrystalline semiconductor material, has a special layer construction but functionally is also used as a starting material for semiconductor devices.
A semiconductor material “A”, for example, monocrystalline silicon in the form of a wafer, is used as the starting substrate. A buffer layer is applied thereto which consists of preferably continuously changing fractions of semiconductor “A” and another semiconductor “B”, the progression normally being from a high “A” fraction and little “B” to a high “B” fraction and little “A”. This is called a “graded buffer layer”. The structure of this buffer layer is full of defects. On the buffer layer, a cover layer is grown which has a composition corresponding essentially to that of the uppermost buffer layer zone. The purpose is the achieving of a low-defect, no-dislocation mixed crystalline layer. These three components—the base or substrate, the buffer layer and the cover layer form the virtual substrate. As known to a person skilled in the art, the application of additional intermediate layers is also conceivable. The actual useful layer is applied to the virtual substrate and has the composition required for the characteristics of the semiconductor material to be achieved. A mixture of two semiconductors can again be used as the useful layer material, but also a layer consisting of a pure semiconductor, for instance “B”. As a rule, this layer is so thin that no dislocations will occur on it but the stress in this layer is maintained (band gap engineering). The epitaxial growth of this useful layer can be combined with the construction of the virtual substrate. However, prefabricated virtual substrates can also be subsequently provided with the useful layer.
The base or the mentioned substrate is first subjected to a plasma-enhanced cleaning, in contrast to previous processes, in which wet cleanings were used within the scope of the production of virtual substrates. Then, the hetero-epitaxial buffer layer is deposited as well as, if required, the above-mentioned cover layer. Optionally, according to the invention, the active layer, which is to be used, is also deposited then, or, after the depositing of the buffer layer, changing over into the cover layer, the actually finished virtual substrate, is made available for a deposition of the active layer which will take place later.
It should be pointed out here that, within the framework of known production processes for virtual substrates (including MBE—molecular beam epitaxy, UHVCVD—ultra high vacuum CVD, ALD—atomic layer deposition, among others), the replacement of the wet-chemical cleaning steps by a plasma-enhanced cleaning step in low-energy plasma by itself is also considered to be inventive and results in significant production-related advantages.
In the course of the addressed industrial manufacturing, it is generally often necessary to subject the parts which subsequently are to be treated by the above-mentioned plasma-enhanced treatment steps (a), (b), (c) first to a cleaning, for example, with respect to ambient-atmosphere-caused surface contaminations.
Furthermore, after each of the above-mentioned plasma treatment steps (a), (b), (c), a cleaning step may be required, for example, for cleaning contamination materials or gases released during the etching.
In an embodiment of the cleaning process, reactive gases (hydrogen, hydrogen—noble gas mixtures) can be used which may impair the materials used for encapsulating the process atmosphere.
It is therefore suggested to provide for such cleaning steps either a relatively low-cost metallic encapsulation, or to bound the cleaning process atmosphere directly by the interior wall of the vacuum recipient exposed to the environment.
The reason is that, for the above-mentioned treatment steps (a), (b), (c) of the parts, as will be explained in the following, non-metallic boundaries of the process atmosphere are considerably preferable; that is, materials which are inert with respect to the used plasma-activated reactive gases. However, in this cleaning step, it must also be ensured that the cleaned surfaces of the part are accessible to the subsequent treatment in an unimpaired manner just as if this treatment were the depositing of epitaxial layers. Thus, also in the case of the plasma-chemical cleaning step of the part, the above-mentioned low-energy plasma with the specified ion energy is used on the surface of the part.
Furthermore, are introduced and removed it is suggested that, in the considered process space, parts which successively, that is, in a serial time sequence, are subjected to at least one of the above-mentioned plasma-enhanced treatment steps and, after the implementation of a defined number of such treatment steps, another plasma-enhanced treatment step takes place in the above-mentioned process space, specifically a process space cleaning step, without a part being introduced into the process space or a substrate dummy being used. This process space cleaning step is preferably implemented in at least two partial steps: First the etching; then the cleaning of etching residues; the latter preferably in a plasma containing hydrogen, noble gas or a mixture thereof.
In view of the object of the invention, particularly in view of the implementation for high up-times, a considered process space is therefore cleaned in a plasma-enhanced manner, after a defined number of treatment steps have taken place. In a process space, parts are normally machined or cleaned either according to one of three methods. However, a case may also occur in which, in a single considered process space, in a programmed sequence, sequentially, in a coated or etched manner, a change of the material composition or, then according to Claim 3, a cleaning of the part is carried out.
The process atmosphere separation provided according to the invention from the vacuum recipient wall permits the subjecting of the process space or of the part to a plasma-chemical cleaning, using reactive gases to which the vacuum chamber wall must not be exposed. The fact that a considered process space, after a defined or definable number of treatment steps of parts can be subjected to a plasma-enhanced self-cleaning and then is immediately available again for the treatment of parts, drastically increases the up-time for the continuous operation. This is compared, for example, with the case that the process space is to be cleaned according to International Patent Document WO98/58099.
Summarizing the previous statements, it is therefore demonstrated that, by means of the production process according to the invention, with respect to quality demands to be made on epitaxy, a coating, a changing of the material composition of the part, an etching of structures on the part or its cleaning can be carried out while avoiding wet-chemical cleaning steps, and in that, between such treatment steps, a self-cleaning of the process space can be carried out, only by changing process parameters, particularly of the admitted reactive gases. The same process can also take place for cleaning the parts in the course of their production according to the invention in that the separation of the process atmosphere and the vacuum recipient is changed or omitted.
The part is preferably subjected in a locally separated manner to at least two of the above-mentioned plasma-enhanced treatment steps and the transport in-between takes place in a vacuum. According to Claim 8, this preferably takes place in a linear movement from one treatment step to the next, in the manner of a linear system or along a circular path, in the manner of a circular system known by the name of “cluster system”. There, treatment stations grouped around a circular transport in a programmed, optionally freely programmable manner are served with parts or workpieces by the circular transport.
In a preferred embodiment of the process according to the invention, the separation between the process atmosphere and the vacuum recipient wall surface takes place by limiting the process space by means of a surface which, in the original condition, is chemically inert with respect to the plasma-activated reactive gas or reactive gas mixture, preferably by means of a dielectric or graphitic surface.
During the operation, thus particularly during the coating (a), the changing of the material composition (b), or the etching (c), particularly the etching of the structure, or also the cleaning, material is deposited on this surface. However, this material is not or only tolerably process-contaminating. Specifically when, in the same considered process space, identical treatment steps are carried out on parts occurring in series, it is even desirable to coat the preferably dielectric or graphitic separating surface which, as mentioned above, is inert in the new condition, with the above-mentioned reaction product materials, however, only to the extent that the resulting coating also adheres in a secured manner to the above-mentioned surface.
The providing of the required inert, preferably dielectric surface can take place such that a structure forming an inert, preferably dielectric surface, is applied directly to the interior surface of the vacuum recipient, whether as a coating with such a material, or by the mounting of self-supporting wall parts with such an inward-facing surface directly to the interior vacuum recipient wall.
In a preferred embodiment, however, the inert surface is spaced away by an intermediate space at least along predominant surface sections from the interior wall of the vacuum recipient. This approach has significant advantages under the aspect of the exchangeability of a separating wall structure also with respect to being servicing-friendly, and under the aspect of a targeted defining of the surface temperatures.
The process space and the above-mentioned intermediate space can be pumped identically or differently. Among other things, this may permit the implementation of an atmosphere in the intermediate space which results in desired thermal conduction ratios between the vacuum recipient wall and the above-mentioned surface. If, in this case, a gas of a high thermal conduction capacity, such as helium, is admitted to this intermediate space, and/or, at least temporarily, a higher pressure than in the process space is implemented in this intermediate space, the heat conduction in this intermediate space is increased with respect to that in the process space, which may make it possible to keep the surface at the desired temperatures. It should be remembered, that below a defined vacuum pressure, the thermal conduction decreases with the pressure and is naturally a function of the thermal capacity of the concerned contained gas.
It should be stressed that when the surface made of an inert, preferably dielectric material is mentioned, this first addresses only the surface material of the surface facing the process space. This surface is preferably formed by that of a separating wall. This surface may be coated; thus, may have a metallic construction facing, for example, the vacuum recipient, with an inert surface facing the process space or the process atmosphere. In this sense, according to Claim 12, the surface can therefore be formed by a layer structure, permitting also the use of diamond-like materials or of diamond.
It is known that, in plasma-chemical processes, the coating rate always increases with a rising temperature (and the acted-upon plasma intensity). As mentioned above, it may be highly desirable to coat the surface facing the process space with reaction products of the plasma-activated reactive gas corresponding to the respective process. However, in this case, considerable attention must be paid to avoiding any peeling-off of the such a coating. These recognitions can be implemented such that, by controlling the temperature of the above-mentioned surface, during the implementation of the plasma-enhanced treatment step, a coating rate of the above-mentioned surface is minimized. This results, for example, in the possibility of selecting this interference coating rate to be significantly smaller than the effective rate on the part, and thus to subject the process space to the self-cleaning only after a relatively large number of completed treatments of parts. There, the above-mentioned coating will be removed before its thickness has reached a critical value, for example, with respect to a peeling-off.
In this case, the effective rate on the part, depending on the treatment, is the coating rate, the penetration rate, the etching rate, the cleaning rate.
It is also within the scope of the object to be achieved according to the invention to pay considerable attention to the degree of automation of the process and the system. It is therefore suggested that a feeding opening for the part be provided in the above-mentioned surface, and that the feeding opening for the treatment of the part be closed by the part and/or by a carrier for the part, at least to such an extent that the floor of charge carriers from the process space is prevented.
As another preferred embodiment, the low-energy plasma discharge is used with an electron source with an electron energy of <100 eV, preferably <50 eV, particularly preferably implemented with a DC discharge; in this case, preferably according to Claim 15, by means of a thermionic cathode, preferably a directly heated thermionic cathode. In a particularly preferred manner, the treated surface of the part is also exposed directly to the plasma.
Also preferably, at least two locally displaced anodes are also provided in the process space for the plasma discharge. These anodes are preferably each separately heatable. By the control of the electric potentials applied thereto and/or their temperature, the plasma density distribution in the process space can be adjusted and controlled dynamically and/or statically. A static adjustment is an adjustment which is set and is kept stationary at least during one treatment step. A dynamic adjustment is the fact that during the treatment step at least one of the above-parameters is changed with respect to the time, whether in the sense of a sweep, periodically, or aperiodically corresponding to defined curve shape in an oscillating manner, or in the form of an arbitrary linear or non-linear ramp function, during the treatment step. Particularly by means of the latter approach, it is possible to take into account the conditions which change during a process step in the process space and act upon these in a compensating manner or also achieve a desired time variation of the plasma density on the surface of the part.
Furthermore, a magnetic field is preferably generated in the process space, which magnetic field, analogous to the above-mentioned parameters anode potential and/or anode temperature, stationarily or dynamically, sets or controls the plasma density distribution on the surface of the part. As a result of the controlled time variation of the magnetic field, the plasma density distribution along the surface of the part can be changed, particularly preferably as if the part were to move periodically in a stationarily distributed plasma. Because of such a sweep of the magnetic field and the oscillating change of the plasma density along the surface of the stationarily held part, the same effect is achieved as if the part were to be moved in an oscillating or rotating manner, but particularly advantageously with respect to the vacuum, without moving parts.
As a result of the fact that the reactive gas is admitted to the process atmosphere in a distributed manner, preferably with an inflow direction essentially parallel to the part surface, and further preferably, with nozzling-in points which are equidistant from the part surface, an optimal exposure of the surface of the part is achieved to the plasma-activated reactive gas, and an optimal utilization of admitted fresh reactive gas, in the sense of an inverse operating ratio, specifically of the quotient of fresh reactive gas admitted per time unit to still fresh reactive gas pumped out per time unit.
For achieving effects as a result of the above-mentioned treatment steps, particularly according to (a), (b), (c) or the cleaning of the part according to Claim 3, of a quality required for depositing epitaxial layers, the partial pressure of background gases, as defined above, is kept at no more than 10−8, preferably at maximally 10−9, according to Claim 19.
The above-mentioned at least one plasma-enhanced treatment step of the process according to the invention, in a preferred first embodiment, is the depositing of a homo- or hetero-epitaxial layer. Also preferably, such a layer is deposited as a silicon germanium layer.
Also an essentially disk-shaped part is produced as the part.
As a further preferred embodiment, the part subjected to the treatment is a silicon wafer or a wafer consisting of a compound semiconductor, preferably of gallium arsenide, indium phosphide, silicon carbide or of glass.
In an extremely important embodiment of the production process of the invention virtual substrates of the above-mentioned type are produced which preferably contain silicon germanium.
In another preferred embodiment of the production process of the invention, parts, particularly the above-mentioned essentially flat or disk-shaped parts, are produced with diameters of at least 150 mm, preferably of at least 200 mm, preferably even of at least 300 mm.
In another preferred embodiment of the production process of the invention according to Claim 27, the coating of parts is implemented at a coating rate of at least 60 nm/min.
In connection with virtual substrates, particularly on a silicon germanium base, normally wet-chemical cleaning processes are used nowadays, whether for cleaning the surface of a finished virtual substrate for additional treatment steps, or for cleaning the surface of an already epitaxially coated substrate for the subsequent preparation of a virtual substrate, whether for cleaning the substrate suitable for epitaxial growth before epitaxially growing the buffer layer. Within the scope of the present invention, it was now recognized that, as a result of the use of the above-mentioned low-energy plasma for a plasma-enhanced cleaning step, the cleaning is implemented such that the subsequent implementation of the production of virtual substrates or of the production of components based on virtual substrates, can take place without any problems. This, that is, the bypassing of wet-chemical cleaning processes by the use of a plasma-enhanced cleaning process, always results in an important advantage and, in addition, this recognition permits the integration of such a plasma-enhanced cleaning into the production process of virtual substrates and of components based thereon. A process for producing a virtual substrate or a component on the base of a virtual substrate, preferably on a silicon germanium base, is therefore suggested which comprises at least one cleaning step which is plasma-enhanced and in which the workpiece is exposed to reactive gas or a reactive gas mixture admitted to a process space. This is activated by means of a low-energy plasma discharge with ion energy at the surface of the part of maximally 15 eV.
The surprising success which the inventors achieved by means of this dry cleaning process in connection with extremely difficult surfaces is attributed to the use of the low-energy plasma, as defined.
A vacuum treatment system according to the invention is specified which is particularly suitable for carrying out the process according to one of the above-mentioned aspects: The interior wall surface of the process chamber in the new condition is implemented of a material, preferably of a dielectric material, which is inert with respect to the plasma-activated reactive gas or reactive gas mixture; according to Claim 30, the process chamber comprising the process space is set off toward the inside from the vacuum chamber wall, that is, is implemented at a distance.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
The invention will now be explained by means of figures.
0 eV<E<15 eV.
As the material of the surface 15 facing the process space PR, a dielectric material, preferably at least one of the materials indicated in the following Group G is used:
Quartz, graphite, silicon carbide, silicon nitride, aluminum oxide, titanium oxide, tantalum oxide, niobium oxide, zirconium oxide, diamond-like carbon or diamond, the latter surface materials being used as coating materials.
In a representation analogous to that of
The wall 14, which actually forms a process space casing within the vacuum chamber together with the wall 1, may consist of the material forming the surface 15a, or the inert material forming the surface 15a is built up, for example, stacked up in layers, on a carrying wall (not shown) which faces the wall 1, which carrying wall, because it is not exposed to the process space PR, can then be constructed, for example, of stainless steel or Inox. By means of the pump connection 11 and the pump 13, the process space PR is pumped down to the partial background gas pressure explained in conjunction with
A person skilled in the art will easily recognize that, also when the same pump 13 is used for pumping down both spaces, specifically the process space PR and the intermediate space ZW, corresponding controllable throttling elements are installed in the assigned pump connection pieces 11 and 11a. With respect to the low-energy plasma, which is used for carrying out the process according to the invention on the module according to
Analogous to the representations of
Irrespective of the processes implemented thereon, the process module structures according to FIGS. 1 to 3 correspond to the invention.
In a representation analogous to FIGS. 1 to 3,
It is clearly demonstrated that the Type I, Type IIe and Type IIne modules can be converted to one another by the corresponding removal or installation of the corresponding process space casing 14, 15b.
As will be demonstrated, in a preferred embodiment, the Type I process module illustrated in
Spaced away from the recipient wall 103, 101 and setting up the intermediate space ZW together with it, the process space casing 113 enclosing the process space PR, analogous to
An anode arrangement acts within the process space PR. As illustrated in
In
In the process space PR, a wafer holder 119 is mounted or—as will be explained in the following—can be introduced into the process space PR in a controlled manner. Although it is definitely possible to provide the substrate holder 119, for the preferred treatment of disk-shaped workpieces 120, defining a carrier surface 119a, with this carrier surface 119a parallel to the diaphragm axis A, at an oblique angle thereto or perpendicular thereto—according to
A workpiece or part to be treated which, as mentioned above, is preferably disk-shaped, is placed through a slotted valve 129 on stationary receiving supports 126, while the wafer or workpiece holder 119 is lowered. Subsequently, the wafer holder 119 is lifted, reaches by means of its carrier surface 119a under the workpiece or the wafer 120, lifts it off the stationary support 126, and moves it upward into the process space PR, while, when the machining position is reached closing off by means of its edge surface 125 the process space to the above-mentioned extent.
The supports 126 are mounted on a workpiece temperature adjusting device 127 which is acted upon by temperature adjusting medium by way temperature adjusting medium feeding and removal lines 128. Normally, the introduced substrate 120 is heated by way of the plate 128a. The wafer holder 119 is illustrated in
The recipient wall 101 and its face-side end plates 103 and 131 are temperature adjusted, preferably cooled. For this purpose, the wall 101 forming the casing is constructed as a double wall, with a temperature adjusting medium system installed in-between. Likewise, temperature adjusting medium line systems are installed into the front plates 103 and 131.
Helmholtz coils 133 as well as distributed deflection coils 135 are mounted outside the vacuum recipient. By means of the Helmholtz coils 133, a magnetic field pattern is generated in the process space PR which is essentially parallel and symmetrical to the axis A. By means of the deflection coils 135, this magnetic field pattern can be displaced in planes perpendicular to the axis A, as schematically illustrated in
Reactive gas is admitted by way of the reactive gas inlet 137 into the process space PR. As illustrated, the reactive gas inlet is preferably arranged coaxially to the axis A in the immediate area of the substrate 120 or the substrate carrier 119 situated in the processing position, with inlet openings essentially parallel to the substrate surface to be treated.
As mentioned above, the vacuum recipient 101, 103, which is preferably made of stainless steel, is cooled intensively. It meets UHV requirements. In this case, the intensive cooling prevents the heating-up of the steel during the process and thus a connected release of carbon-containing gases from the steel.
With respect to the material of the process space casing 113, particularly its surface exposed to the process, the statements made by means of
In the case of process modules Type I, the vacuum chamber wall, usually made of stainless steel, is not coated because it is protected from the reactive gases and the plasma by the process space casing 113; also, because, as illustrated in
The process space casing 113 is preferably constructed in several parts (not shown), so that it can be removed or exchanged without demounting the anode arrangement 117a, 117b. By the removal of the process space casing 113 illustrated in
The following is a compilation of the processes carried out in each case by means of the process modules introduced by means of FIGS. 1 to 5.
Type I
While meeting quality requirements existing when coating parts by means of an epitaxial layer, this process module is used for carrying out reactive coatings in a plasma-enhanced manner, or plasma-enhanced reactive etching, or plasma-enhanced reactive altering processes ranging from the material composition on the workpiece to defined penetration depths; or, particularly combined with the above-mentioned process steps according to the invention, the surfaces of the workpieces or parts are subjected to a plasma-enhanced reactive cleaning, particularly in hydrogen plasma. After passing through a defined number of the above-mentioned treatment steps or as required, these Type I process modules are subjected to a self-cleaning without introducing a workpiece part or using a substrate dummy. This self-cleaning comprises preferably, on the one hand, a plasma-enhanced reactive etching step; on the other hand, a subsequent plasma-enhanced reactive cleaning step for etching residues, preferably carried out in a hydrogen plasma.
Type II
The Type II process modules are used for cleaning workpieces in a more penetrating manner, as required, for example, when they are supplied to the above-mentioned treatment steps, which meet epitaxial quality requirements, from the ambient atmosphere. Also in these Type II process modules, in combination with the treatment processes meeting the above-mentioned highest quality demands, the parts are cleaned by means of the above-mentioned low-energy plasma, in a reactive manner, preferably first by a plasma-enhanced reactive etching, then by a plasma-enhanced reactive cleaning, preferably in hydrogen plasma.
With respect to preferred coating processes, specifically for the depositing of hetero- or homo-epitaxial layers by means of the Type I modules, reference is made to the complete contents of the approach according to the initially mentioned International Patent Document WO98/58099.
As mentioned initially, a preferred process of this type is the production of virtual substrates. Accordingly, in the Type II process module, the base, suitable for a subsequent hetero-epitaxial layer growth, is reactively cleaned in a plasma-enhanced manner, using a halogen, but preferably hydrogen, as the reactive gas. Subsequently, in one or several of the subsequent Type I process modules, the hetero-epitaxial layer is grown such that the lattice constant is changed and, by the successive graded building-in of another material, a surface structure is achieved which is as free of defects as possible. Then—in another Type I module—optionally the epitaxial growth of the semiconductor layer to be used is implemented in a definably mechanically strained manner for adjusting the band gap and setting the desired semiconductor characteristics, as, for example, the charge carrier mobility. Optionally, additional treatment steps according to the invention will follow until the finished virtual substrate is unloaded from the system 144.
A person skilled in the art is definitely familiar with the fact that, also during the production of the virtual substrate, additional layers can be built in, or that cleaning steps can be provided between the coating steps, preferably as “soft cleaning steps” in a Type I process module.
Although schematically,
The described process modules, which can all be converted into one another, can treat substrates which have a diameter of at least 150 mm, preferably of at least 200 mm, preferably even of at least 300 mm. In the case of the epitaxial coating by means of the processes described in the above-mentioned International Patent Document WO98/58099, which is enclosed as Attachment A with respect to the process disclosure of the present application, coating rates of at least 60 nm/min. are reached at the above-mentioned substrates.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09792055 | Feb 2001 | US |
| Child | 11271738 | Nov 2005 | US |
