DE3634130A1 - DEVICE AND METHOD FOR CHEMICAL VAPOR DEPOSITION - Google Patents

Description

The invention relates generally to the chemical Evaporation or chemical vapor deposition of materials on a substrate and in particular on the application an axially symmetrical gas flow for the purpose of improvement the deposition of a material carried by the gas on a substrate.

In the field of chemical deposition of a material on a substrate it is known, a susceptor or a receiving device to be provided in a closed container, the typically carries a variety of substrates. In the Close to the pick-up device is in the container Carrier gas that is to be deposited on the substrate or contains atoms to be deposited in gaseous form. The gas flow caused by the geometry of the container and the receiving device is determined, in general forced to flow parallel to the substrates. Because of a combination of transportation and chemical The atoms of the deposition material stick at high reaction Temperatures on the substrate surfaces and form the desired precipitation layer. This separation technique  has proven satisfactory in the past, but needed as larger volumes of material and Higher quality materials have been requested reached the limits of this technique. The separation technology has four problems. The first problem is that by depositing the material on the surface the concentration of the deposition material in the carrier gas changes when the gas over the surface of the substrate and of the receiving device flows. Accordingly, one finds over the length of the cradle and also over the length a different growth rate of each substrate Material layer. The second problem is that in the large reaction vessels used for the separation new separation material over a relatively long time Routes must be transported when the separation material is exhausted in the separation region. These deposition controlled by transport limits the rate or speed at which the deposition or the evaporation can take place and is therefore related at the cost of manufacturing the materials, e.g. B. in the epitaxial process. A third problem will arise usually referred to as self-doping (autodoping). In the process of self-doping, foreign atoms can escape the highly doped substrate from the substrate surface solved and over the gas phase in the less doped Layer of material that is deposited can be introduced. So far, special steps have had to be taken to reduce self-doping, e.g. B. the application a separate cover on the back of the Substrate. Another problem is pollution with particles (particulate contamination). With growing chambers for chemical vapor deposition the area of the chamber wall too. Unwanted deposits, that form on these walls Sources for particles that are inadvertently in the deposition material  can be introduced.

There was therefore a need for a vapor deposition technique or vapor deposition at which the growth rate of the material deposited on the substrate via the entire surface of the substrate is extremely uniform which increases the growth rate of the deposited material can be the self-doping of the deposited Prevents material without additional process steps can be and where the contamination with particles can be reduced.

Accordingly, an object of the invention is a method and an apparatus for improved chemical Vapor deposition of a material to create a substrate.

Another object of the invention is a method and an apparatus for effecting an improved one to create chemical vapor deposition of materials where the concentration of the separation material in the carrier gas over the entire surface of the substrate is substantially uniform.

Another object of the invention is to provide a chemical vapor deposition of a material on a substrate to achieve, in which the substrate and the flow of the Carrier gas have an axial symmetry.

Another object of the invention is to provide a chemical vapor deposition of a material on a substrate provide by a stagnation point flow makes use of the carrier gas. Another object of the invention is a steady flow of Steam directly against a substrate for chemical purposes  Vapor separation of materials contained in the steam are or are borne by it.

Another object of the invention is to provide a Reaction chamber for growth by chemical vapor deposition a uniform axially symmetrical gas flow against one provide circular substrate in that a A plurality of openings is provided through which the Carrier gas can pass through with the separating material.

Another object of the invention is to be uniform Growth rates of material in a chemical vapor reaction chamber to achieve an axially symmetrical gas flow applied to a substrate and rotated the substrate becomes.

Another object of the invention is to provide a Reaction chamber for chemical vapor deposition uniform removal of the gaseous substances following the deposition Products.

Another object of the invention is to provide a Reaction chamber for chemical vapor deposition suitable technique for controlling the rate or speed to provide the deposition of the deposition material on a substrate.

The above and other objects are achieved according to the invention through a chemical vapor deposition reaction chamber reached in which one in a predetermined Gas introduced from a circular substrate an initially uniform velocity to the substrate has. When the gas gets to the substrate it becomes radially outward in an axially symmetrical flow redirected. The gas is passed through a variety of openings,  a series of baffles or other means that essentially preserve the axial symmetry of the gas flow, withdrawn from the chamber. The circular substrate can be rotated for greater uniformity of the Deposition by averaging irregularities in the To reach gas flow. The distance between the substrate and the gas introducing device can be changed will. In addition, the axial symmetry of the gas flow is reduced self-doping of the deposited material. The radial gas flow and the small wall area of the separation chamber together reduce pollution of the growing film with particles.

These and other features of the invention appear in further details from the following description of Exemplary embodiments with reference to the drawing.

The drawing shows:

Fig. 1a-1c - in each case in schematic view, - the flow of the deposition material gas containing on substrates according to the typical arrangements according to the prior art,

Fig. 2 is a schematic representation in which the gas flow is according to the invention initially directed uniformly to a circular substrate,

Fig. 3 is a cross-sectional or side view of the gas flow according to the invention, brings the deposition material to the substrate,

Fig. 4 is a schematic representation of a device for providing the initial conditions for the gas flow according to Fig. 3,

Fig. 5a is a cross-sectional view of the device from above, showing the position of baffles to maintain the axial symmetry of the gas flow according to the invention, and

Fig. 5b is a horizontal cross-sectional view of a portion of the device showing the position of the baffles of Fig. 5a with respect to the semiconductor substrate to create a uniform gas flow.

FIG. 1 a shows a multiplicity of substrate materials 10 , which are arranged on a receiving or susceptor material 15 . A gaseous substance 11 crosses the substrate material and deposits predetermined components of the vapor on the substrate. FIG. 1b shows a susceptor geometry in which a plurality of areas 13 are each a plurality of substrates 10 can bear so that these are exposed to the flowing gas 11 over the surfaces. Fig. 1c shows a geometry in which a susceptor 15 supports a plurality of substrates 10. The gas carrying the separation material is introduced through an opening 14 in the middle of the susceptor.

FIG. 2 shows in a schematic representation that the gas 11 carrying the vapor deposition material or materials is directed or directed directly onto a substantially circular substrate 10 carried by a susceptor 15 . The gas first flows against the surface and then in a radially outward direction away from the axis of the susceptor / substrate combination.

FIG. 3 shows a cross-sectional view in a plane that contains the axis of symmetry of the flow of the gas 11 approaching the substrate 10 . The gas 11 initially has a substantially uniform velocity perpendicular to the entire surface of the substrate 10 . When the gas 11 comes to the substrate, the solid substrate causes the velocity vector to lie parallel to the surface of the substrate 20 and point away from the axis of symmetry. At a point 21 on the axis of symmetry, usually referred to as a stagnation point, there is theoretically no gas flow. The axially symmetrical gas flow resulting from the uniform gas flow against or onto a surface is generally referred to as a stagnation point flow.

Fig. 4 shows a practical embodiment of a device for creating the initial conditions of a gas with a velocity vector of uniform size directed against the substrate. The gas 11 is supplied to an area above a surface 71 which can either be a surface of a housing or one of two substantially parallel plates. The gas 11 is driven against the semiconductor substrate 10 through openings 74 in the surface 71 . The initial vector of the speed is thus directed towards or towards the substrate. Because the openings 74 are relatively small in size, the gas velocity across all of the openings 74 is substantially uniform as the gas passes to the plane of the substrate. To reduce the effect of any "granularity" that may result from the use of discrete orifices and to smooth out any irregularities in gas distribution, the substrate 10 can be rotated during the gas flow period. It has been found that a substantially uniform gas flow can be obtained if the openings 74 are located on the apexes of equilateral triangles and are evenly distributed over the area of surface 71 of approximately the same size as the substrate 10 and thus axially symmetrical.

FIG. 5 a shows a top view of the means for removing the gas from the chamber without changing the axial symmetry in the vicinity of the substrate 10 . In one embodiment, many relatively large openings 53 are located at substantially the same distance from the axis of symmetry of the gas flow and the gas is removed through these openings. This design can result in a large structuring in the gas flow in the vicinity of the substrate 10 without additional means. In order to reduce this structuring, guide plates 51 and 52 can be inserted between the substrate and the openings 53 . As a result of the deflection of the gas flow, this structure smoothes and therefore favors the axial symmetry of the gas flow. It is apparent that the actual deviation from the axial symmetry in the vicinity of the substrate 10 can be largely reduced even without baffles 51 and 52 if a plurality of openings 53 extending around the semiconductor substrate can be used and the number of these openings is big enough. FIG. 5b is substantially a horizontal partial cross-sectional view 52 and 51 and the openings 53 represents the relationship of the guide plates to the substrate 10 and the susceptor or the holding device 15.

Operation of the preferred embodiment:

Chemical vapor deposition or vapor deposition of material onto the semiconductor substrate is the result of a gas flow along the surface of the semiconductor substrate 10 , which gas flow is essentially forced to be axially symmetrical. This flow design is commonly known as stagnation point flow. Under these conditions, the density of deposition material carried by the gas and deposited on the substrate is essentially uniform over the entire surface. This result is known from the study of this flow configuration in other applications and the results have been confirmed by computer simulation studies carried out by the inventors under the conditions determined by the parameters of the deposition reactor. Gas, which has the original density of deposition materials, can come into contact with the surface due to both the convection and diffusion processes due to the expanding area found when moving away from the axis of symmetry. Furthermore, it is known from studies in other physical areas and confirmed by computer simulation studies that the temperature profile of the impinging gas is essentially uniform in the radial direction. This means that the isotherms across the substrate are at a constant distance from the substrate surface. Similarly, for chemical reactions occurring in the gas, the mole fraction or ratio of the gas components at a given distance from the substrate surface is substantially radially uniform.

Since it is practically necessary to pass the gas through a series of Make openings to meet the required initial conditions bring about, and since it’s difficult to do that circular semiconductor substrate with respect to the entering and centering the outflowing steam can do that Substrate are rotated to represent the substrate to reduce uneven structures in the carrier gas.

So far, the discussion has focused on the special one  Gas flow with respect to the substrate but it is obvious that certain other characteristics are significant.

For example, if the substrate needs to be heated and especially when the substrate is exposed to optical radiation To be heated is the openings through which the Gas is introduced, essentially containing the device made of a suitable transparent material, e.g. B. fused quartz. It is also obvious that, although the device is in horizontal Flat substrate and impinging from above Steam was shown, this orientation can be varied can without the operation of the preferred embodiment will be changed.

An important aspect of the present invention is the ability to control the distance, as shown in FIG. 4, between the gas introducing device and the substrate. The ability to determine this distance is an essential means of controlling the growth of the deposited material on the substrate 10 . The axially symmetrical flow of the gas (away from the axis) has the significant advantage of reducing self-doping by generating a gas flow in a direction with respect to the substrate that is opposite to the flow of material causing self-doping. This effect can be promoted and the self-doping can be further reduced in that a flushing gas is fed to the bottom of the substrate.

This technique of chemical vapor deposition is special for epitaxial deposition and especially for the deposition of epitaxial silicon on a substrate of benefit. The above description only provides one Embodiment again and is intended to be within the scope of the invention not restrict. The person skilled in the art can make many modifications  make without departing from the scope of the invention is exceeded.

Claims (18)

1. Device for the chemical vapor deposition of materials on a substrate, with a substantially circular substrate, characterized by a device for generating a gas flow (gas flow device) which is axially symmetrical across the circular substrate. 2. Device according to claim 1, characterized in that the gas flow device uses the gas essentially uniform velocity perpendicular initiates to the substrate. 3. Device according to claim 2, characterized in that that the gas flow device means for Changing the distance between the substrate and one Area where the gas is directed against the substrate having. 4. The device according to claim 3, characterized by a Device for rotating the substrate. 5. The device according to claim 3, characterized in that the gas flow device a variety of openings for withdrawing the gas without significant Has change in the axial symmetry. 6. The device according to claim 5, characterized by a  Variety of baffles between the substrate and the pull holes. 7. The device according to claim 1, characterized by a Device for reducing the self-doping of the Substrate. 8. The device according to claim 7, characterized in that that the gas flow device means for Maintaining a stagnation point flow of the Has gas. 9. The device according to claim 1, characterized in that the gas flow device is a device having a flow of the deposition material containing gas perpendicular to the circular Substrate aligns. 10. The device according to claim 9, characterized in that the distance between the facility and the substrate is changeable. 11. The device according to claim 9, characterized in that the substrate is rotatable. 12. The device according to claim 9, characterized in that that the device for the epitaxial Deposition is used. 13. The apparatus according to claim 12, characterized in that the facility for separating epitaxial silicon used on the substrate becomes. 14. The apparatus according to claim 9, characterized by a  Device for introducing a purge gas to an opposite one Side of the substrate. 15. Process for chemical vapor deposition of material on a substrate according to claim 1, characterized characterized in that the containing the deposition materials Gas under essentially axial symmetry of the substrate and the gas flow are fed to the substrate becomes. 16. The method according to claim 15, characterized in that the deposition rate through Changing the distance between the substrate and the the gas supply device is controlled. 17. The method according to claim 15, characterized in that the substrate is rotated. 18. The method according to claim 15, characterized in that a stagnation point flow of gas is maintained.