NL8602356A - APPARATUS AND METHOD FOR AN AXIAL SYMMETRICAL REACTOR FOR THE CHEMICAL VAPORIZATION. - Google Patents

Description

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Apparatus and method for an axially symmetrical reactor for chemical precipitation from vapor.

The present invention generally relates to the chemical deposition of material supported by a gas on a solid substrate, and more particularly to a chemical vapor deposition reactor having axial symmetry.

It is known in the prior art to provide chemical vapor deposition material, such as epitaxial chemical vapor deposition, by passing a gas containing the reacting materials over a solid substrate. The gas includes the material to be deposited on the substrates. The solid substrate generally needs to be kept at an elevated temperature to maintain the reaction with the surface. The deposition can typically be accomplished within a container, which causes the flow of gas over one, or more particularly, a variety of substrates placed on a base or a support member.

Several problems can arise with prior art chemical vapor deposition reactors. In particular, the precipitation reaction with the substrate removes vapor deposition materials from the flowing gas and results in a variation in the concentration of reactants in the gas. Because the gas is forced to flow over a slab of substrate, the variation in concentration may result in an unevenly deposited layer. This non-uniformity of deposition layers can occur for a variety of substrates and can occur over a single substrate. In addition, systems currently used have limited ability to provide a uniform temperature for a variety of substrates or even a single substrate. Temperature uniformity is typically achieved by combining a large thermal mass with the substrate. The large thermal mass and associated thermal inertia cannot limit uniformity in the temperature distribution of the substrates. However, the large thermal mass limits the extent to which the substrate can be thermally equilibrated and may therefore have a detrimental effect on the time required to treat the substrates. The high thermal mass can therefore directly affect productivity.

In addition, chemical vapor deposition reactors currently used for epitaxial deposition may allow autodoping, doping of the precipitating material resulting from evaporation of 1-2-3.

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2 dopant from the reverse side of the typically substantially doped substrate. In prior art reactors, care had to be taken to seal the reverse side of the substrate to prevent auto-doping.

In an effort to increase the productivity of chemical vapor deposition reactors, the reactors have been increased in size to accommodate more substrate material. This increase in size resulted in increased particle contamination of the substrate. The particulate material arises from unwanted material deposition on the reactor walls, precipitation which can become detached from the walls and enter the deposition region.

In typical vapor deposition systems, gaseous composition, temperature and autodoping can be controlled, but further control of the precipitation process has been sought.

Recently, studies have been conducted on the possibility of using an axially symmetric flow of gas over each substrate to provide a more satisfactory vapor deposition method. With the axially symmetrical flow and appropriate boundary conditions, a more even precipitation layer can be obtained. Single slab precipitation allows flexibility in the heating process and allows heating and cooling time to be limited. The axial symmetric gas flow has the further advantage that autodoping, the unwanted doping of the deposition layer by atoms from the substantially doped substrate, can be limited. In addition, the axially symmetrical flow of gas allows larger substrates to be used, creating some slab reactors. The single wafer reactors tend to limit particulate contamination of the deposition regions of the substrate.

Therefore, there is a need for a chemical vapor deposition reactor which can advantageously utilize an axially symmetrical gas flow and additionally provide uniform heating so that a small thermal mass can be combined with the substrate.

It is therefore an object of the present invention to provide an improved chemical vapor deposition reactor.

It is another object of the present invention to provide a chemical vapor deposition reactor for an axially symmetrical substrate.

Moreover, it is another object of the present invention to provide a chemical vapor deposition process with an axially symmetrical geometry.

Moreover, it is a further object of the present invention to provide an apparatus and method for uniformly heating a substrate with a circular geometry.

in addition, it is another object of the present invention to provide a reactor for chemical vapor deposition with an apparatus which can provide further control of the precipitation process.

Moreover, it is a further object of the present invention to provide a vapor deposition reactor for which the flow of gas carrying the reactant material over the substrate has axial symmetry.

The above and other objects are accomplished according to the present invention by a circular reaction chamber apparatus for chemical vapor deposition of materials having a substantially circular substrate. The circular substrate is carried on a base or support member with a base. Gas carrying material to be deposited on the substrate is sent to the substrate surface with substantially uniform velocity perpendicular to the substrate surface through devices arranged at a controllable distance from the substrate. The gas is generally limited to have an axially symmetrical flow over the surface of the substrate. A radiant heating device is provided to heat the substrate and associated device to an even temperature. The temperature uniformity achieved by the heating device allows the substrate and the associated device to have a relatively small thermal mass. The small thermal mass allows the thermal equilibrium for a given substrate temperature to be reached quickly. The pedestal supporting the substrate can be rotated for further temperature and precipitation uniformity. A further flow of gas can be introduced to limit autodoping of the deposited layer.

These and other features of the present invention will be understood upon reading the description below together with the drawings, in which: Figure 1 is an exploded schematic view of the vapor deposition reactor chamber according to the invention, Figure 2 is a schematic cross-sectional view of the reactor chamber of the invention for vapor deposition; Figure 3 is a schematic cross-sectional view of the reactor chamber of the invention showing a further detail of the preferred embodiment; and Figure 4 is a cross-sectional view of the base for providing a further flow of gas to limit autodoping of the material deposited on the substrate.

Figure 1 shows an exploded schematic view of the device comprising the chamber for chemical vapor deposition of the reactor. The reactor chamber arrangement includes an up and down heating chamber 60. A plurality of radiant heating elements 50 are connected to the two chambers. These heating elements 15 are typically elongated lamps, while the individual chambers can typically have a square shape in the preferred embodiment. As will be appreciated, a different chamber geometry may be used. The lamps are inserted through openings in the walls of the chamber and are arranged substantially parallel to the other lamps and placed in a plane parallel to the substrate 10. The above and lower chamber are arranged essentially such that the lamp assembly of each chamber is at right angles to the other lamp assembly. The substrate 10 and the associated support member 15 are carried through the base 80 into the reactor. The gas 11 carrying the materials to be deposited on the substrate 10 is introduced into the reactor chambers through device 70. Device 70 mainly consists of quartz (for transferring heating radiation) and comprises a chamber into which gas 11 is introduced. The device 70 has a surface facing the substrate surface and substantially parallel to it. This surface has a plurality of openings that allow release of the gas with a substantially uniform flow to the substrate.

Figure 2 shows a cross-sectional view of a reactor for chemical vapor deposition. The lamps 50 in the two heating chamber 60 provide for uniform heating of the substrate 10 and associated holding body 15. The lamps are not shown at right angles in Figure 2 to illustrate two heating lamp embodiments. In the lower heating lamp embodiment, parabolic reflectors direct the radiant energy to the support member 40 and associated substrate 10. In the upper chamber 60 of Fig. 2, 8602356 5, the outer heating lamp 50 combines parabolic riot vectors. The internal heating lamps are arranged for a flat area 52. On the flat area and the parabolic reflectors, coating has provided significant reflective material to direct the radiation 5 to the combination substrate support. The substrate / support member combination is carried by a pedestal 80, and although not shown in Figure 2, the base of the pedestal extends through a heating chamber 60. The device 70 for supplying the gas containing the precipitate material to the substrate has an inlet 10 for receiving gas 11 and a plurality of openings 74 for uniformly directing the gas to the substrate 10. Device 90, not shown in detail, is a device for discharging the gas from the precipitation chamber in a manner to maintain the axial symmetry of the gas flow. Device 90 may comprise a plurality of openings 15, the main function of which is to control the gas flow. Device 90 also provides a source of heat loss comprising temperature uniformity across the combination substrate support.

Figure 3 shows a more detailed embodiment of the reactor-20 chamber. The chambers 60 include lamps 50 which are electrically and mechanically coupled to the rest of the device by coupling device 51 and may have a reflection area associated therewith as shown in Figure 2. Device 70 includes a first flat material 72 and a second plane material 71. The planar material 71 is substantially parallel to the substrate 10 and has a plurality of openings for sending gas 11 to the substrate. Substrate 10 is supported by pedestal 80. The gas is obstructed from flowing along a plurality of baffles 91 to maintain an axially symmetrical flow. The substrate and the top of the pedestal are generally enclosed by plate 71, plate 75 and external surfaces 76 to restrict the flow of gas. The gas can also be vented from the enclosure through a plurality of openings. Casing 8 is connected to the heating chambers 60 and has further, not shown, devices for connecting the top and bottom parts of the reactor parts and for carrying the internal casing device.

Figure 4 illustrates a method of inhibiting autodoping of the deposit layer. The axially symmetrical flow of gas flows outwardly to the edges of the substrate 10. The substrate 40 10 is supported above holding members 15 by spacers 16. The 8602356 6 holding member is supported above the base 80 by risers 81 and through the vertical walls of the pedestal 80. A gas 13 flows through a passage in the pedestal 80, through an opening 83 in the retainer 15 to the space between the retainer and the substrate. This radially outwardly directed flow, together with the radially outwardly directed flow of the carrier gas 11, carries unwanted substrate doping atoms away from the precipitate portion of the substrate.

The construction of the chemical vapor deposition reactor is designed to take advantage of the beneficial effects of an axially symmetrical flow of carrier gas over a substrate. This gas flow embodiment, also referred to as stagnation point flow, provides the advantages of being radially uniform in the concentration of the deposition materials in the vicinity of the substrate, radially uniform in the temperature of 15 isotherms in the gas above the substrate surface, and radially uniform the extent of chemical reactions in the gas and on the substrate surface.

The device 70, which in the preferred embodiment may comprise plates of material with openings in the plate nearest the substrate, provides an appropriate technique for introducing the axially symmetrical gas flow into the chamber. In the preferred embodiment, the openings are provided at the apexes of equilateral angles. Devices, such as the baffles 91, are provided to ensure that the carrier gas removal process does not significantly interfere with the axially symmetrical flow of gas. The device 70 is typically constructed of a material that can transfer a large portion of the radiation to the combination support-substrate substrate.

The heating chambers are configured accordingly to promote the axial symmetry of the deposition and to maintain a uniform temperature across the substrate. The plurality of lamps 50 are disposed within the heating chambers. A highly reflective material is applied to the walls of the chambers 53 as well as to the reflective area 52 and the parabolic reflectors 51 to increase the thermal efficiency and to increase the range of actual heat sources 35 seen through the resulting substrate. For example, in Figure 2, the edge of the substrate is not exposed to the same radiation as the rest of the substrate due to the lack of heating sources in the direction of region 90. To compensate for this cooler environment, the outer heating lamps can be operated with additional power 40, thus radiant heating in the area is increasing 8692356 7. Varying the position of the heating elements, by tilting the outer heating lamp assemblies or extending the heating chamber considerably beyond the substrate, can also be used to compensate for the increased heat losses from the exterior area of the substrate. The side of the heating chamber can be provided with significant reflective material, providing the effect of additional heating sources as seen from the substrate due to the reflected radiation. The orientation of the heating lamps is radiated from the orientation of the heating lamps in the other room to further limit the structure resulting from the use of discrete heating sources. The pedestal carrying the substrate can be rotated to provide further limitation to any residual thermal structure.

Figure 4 shows an embodiment of the present invention in which a stream of gas 13 can be used to limit autodoping. The flow of gases 11 and 13 carries dopant materials evaporated from the bottom of the substrate from the surface of the substrate receiving the deposited materials. The pedestal typically consists of a material that is translucent to much of the spectrum of the heating radiation.

Thinning or removing the support member carrying the substrate can reduce the mass that must be heated to achieve thermal equilibrium.

By limiting the thermal mass, more substrates can be treated simultaneously and a greater productivity can be achieved.

The substrate can be appropriately moved up or down relative to the plate, thereby introducing the carrier gas. This positioning flexibility provides for further control of the precipitation conditions.

A further source of non-uniformity is the radiation field experienced by the combination substrate-substrate combination due to the absorption properties and temperature of the device 70, pedestal 35, and other structural members to be placed between the radiation sources and the combination substrate retaining member. Account must be taken of disturbances arising in the radiation field arising from the presence of those elements, such as the thermal influence of the structural members arising from absorption and emission of radiation.

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The above description is given to illustrate the operation of the preferred embodiment and is not intended to limit the scope of the invention. From the above description, many variations will be apparent to those skilled in the art which will still lie within the scope and scope of the present invention.

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Claims (19)

A chemical vapor deposition reactor on a heated substrate comprising: 5 circular means substrate means, characterized by heating means for uniformly heating said substrate means; and gas flow means for providing an axially symmetrical flow of gas over the substrate means. 2. A chemical vapor deposition reactor as claimed in claim 10 1, characterized by support means for carrying the substrate means, which support means make it possible to control a distance between the gas flow means and the substrate means. 3. Reactor for chemical vapor deposition according to claim 1, characterized by support means for supporting the substrate, which support means can rotate the substrate. A chemical vapor deposition reactor according to any one of the preceding claims, characterized in that the gas flow means comprises devices for introducing the gas at a uniform rate perpendicular to a surface of said substrate. The chemical vapor deposition reactor according to any one of the preceding claims, characterized in that the heating means comprises a first and a second chamber, at least one of said chambers comprising a plurality of heating lamps. 6. A chemical vapor deposition reactor according to claim 25, characterized in that at least part of the interior walls of the chambers are covered with a substantially reflective material. Reactor for chemical vapor deposition according to any one of the preceding claims, characterized in that the axially symmetrical flow of gas allows a gas stream shape with stagnation point. 8. A chemical precipitation reactor characterized by a chamber having a plurality of apertures, said apertures being substantially axially symmetrical with respect to and substantially equidistant from the substrate means; the heating means comprising a plurality of heating lamps providing a substantially uniform temperature in the substrate means, and at least one opening arranged substantially symmetrically about a circumference of the circular substrate means. 9. A chemical vapor deposition reactor according to claim 8, characterized in that the chamber is made of a material which allows radiation to pass through it. 8602356 A chemical vapor deposition reactor according to claim 8, characterized by opening means below the substrate means for introducing a second flow of gas into said substrate means. 11. Chemical vapor deposition reactor according to claim 5, characterized in that the lamps are arranged above and / or below the substrate means. The chemical vapor deposition reactor according to claim 8, characterized in that the substrate agent is carried by a support member. The chemical vapor deposition reactor according to claim 8, characterized in that the chamber and the at least one opening are configured to provide a stagnant point gas flow. 14. A chemical vapor deposition reactor according to claim 8, characterized by a first heating chamber disposed at a first side of the substrate agent and a second heating chamber disposed at a second side of the substrate agent, the first and second heating chamber comprising the plurality of heating lamps, wherein the heating lamps of the first chamber are arranged substantially at right angles to the heating lamps of the second chamber. A chemical vapor deposition reactor according to claim 6, characterized by means for rotating the substrate means. 16. A method of chemical vapor deposition using the reactor according to any one of the preceding claims, characterized by: realizing a uniform substrate; uniformly heating the substrate to a certain temperature; and flowing a gas along the substrate, the gas flow having axial symmetry, and the gas comprising material for precipitation on that substrate. A method of chemical vapor deposition according to claim 16, characterized by rotating the substrate. A method of chemical vapor deposition according to claim 16 and / or 17, characterized by introducing a second gas flow along a second surface of the substrate to limit autodoping. 19. A chemical vapor deposition method according to claim 16, characterized in that the gas flow step comprises generating a stagnant gas flow ring relative to the substrate. 3602356