JP2008034780A - METHOD FOR MANUFACTURING SEMICONDUCTOR SiC SUBSTRATE WITH EPITAXIAL SiC FILM, AND ITS EPITAXIAL SiC FILM-FORMING DEVICE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epitaxial SiC film-forming device by which doping concentration distribution of an epitaxial SiC film formed on an SiC substrate is made homogeneous even when an area of the SiC substrate is enlarged. <P>SOLUTION: In the epitaxial SiC film-forming device, a first hot wall 2 and a second hot wall 7 are, in a heat-resistant cylindrical pipe which has a reactive gas inlet port and an outlet port on both ends thereof and can be reduced in pressure, arranged side by side in a central axial direction, with a thermal insulating material in-between. A supporting member for fitting an SiC crystal substrate 4 is arranged in a reaction chamber space provided to the first hot wall 2. A device for induction-heating the first hot wall 2 is provided to the outer periphery of the heat-resistant cylindrical pipe at a position facing the first hot wall 2. The second hot wall 7 comprises a gas path which is provided therein in a direction parallel to the axis of the heat-resistant cylindrical pipe, and whose one end is connected to the reactive gas inlet port to rectify inflow reactive gas and the other end leads to the reaction chamber space in the first hot wall 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor SiC substrate in which a SiC single crystal film is formed on a silicon carbide (hereinafter referred to as SiC) substrate, and an apparatus for forming the SiC single crystal film.

  A SiC semiconductor substrate for a semiconductor device is usually composed of a SiC single crystal substrate and an epitaxial SiC film formed thereon. In order to provide the SiC semiconductor substrate with a function as a semiconductor device, various device structures are further created in the epitaxial SiC film. Therefore, the properties of the epitaxial SiC film formed first, particularly its film thickness, The uniformity of the doping concentration within the film surface is an important requirement for improving the characteristics and the yield rate of the final semiconductor device. It is known that the uniformity of the doping concentration is greatly affected by the uniformity of the reaction gas temperature used for epitaxial growth of the silicon carbide crystal film in the film forming apparatus.

  When the SiC film is formed by epitaxial growth, it may be epitaxially grown usually in a high temperature furnace of 1500 ° C. to 1700 ° C., or even 2000 ° C. or higher. For this reason, an induction heating apparatus is often used as a heating source capable of obtaining an extremely high temperature as described above. Further, as described later, when the internal member in the quartz tube heated by induction heating is only the first internal member, it is caused by the temperature difference between the first internal member (for example, wafer support member-susceptor) and the wafer. Then, since the coating material of the internal member is peeled off, a hot wall having a schematic configuration as shown in FIG. 2 is further provided that surrounds the periphery of the wafer with a second internal member (hot wall) that is heated by induction. Generally used.

  FIG. 2 is a schematic cross-sectional view of the heating unit 20 of a typical horizontal hot wall film forming apparatus as a SiC epitaxial film forming apparatus. FIG. 2A shows a cross section obtained by cutting the quartz tube along the axial direction at a position where the main surface of the SiC single crystal substrate (hereinafter abbreviated as a unit wafer or SiC wafer) placed in the quartz tube can be seen from above. (B) is a cross-sectional view of the quartz tube cut along the axial direction in the cutting direction in which the thickness of the wafer appears, and (c) is a longitudinal cross-sectional view of the quartz tube cut in the ring direction at the wafer position. It is.

  The heating unit 20 is inclined on the quartz tube 21, a hot wall 22 as a second internal member disposed inside through a heat insulating material 26, a susceptor 23 with an inclined surface as a first internal member, and the susceptor 23. The wafer 24 is supported by being attached thereto, and a high-frequency coil 25 wound around the quartz tube 21. When a reaction gas 27 (arrow) for forming a SiC epitaxial film on the wafer 24 is introduced from an inflow port (not shown) and reaches the heating unit 20, the temperature is increased by induction heating by the high frequency coil 25 to about 1600 ° C. The SiC single crystal film is formed by epitaxially growing SiC by reacting on a wafer 24 inclined and attached to the susceptor 23 placed in the reaction chamber space in the hot wall 22 in the quartz tube 21 at a high temperature. A film is formed.

  Regarding the film forming conditions, the quartz tube 21 is kept at a low pressure of about 80 Torr (1 Torr is 133.332 Pa), and a reaction gas 27 made of monosilane, propane, hydrogen, etc. is 10 liters from an inlet (not shown) at the end of the quartz tube. Flow at a flow rate of / min. In the heating unit 20 at the center of the quartz tube 21, the hot wall 22 such as graphite in the tube is heated to a high temperature of about 1500 ° C. to 1700 ° C. by induction heating by a high frequency coil 25 wound outside the quartz tube 21. At this time, the wafer 24 is heated to about 1600 ° C. by heat conduction through the graphite susceptor 23 in contact with the hot wall 22 and radiation from the hot wall 22. Further, the reaction gas 27 is heated and reacted by heat conduction due to contact with the hot wall 22 to form an epitaxial SiC film on the wafer 24. The hot wall 22 and the susceptor 23 are preferably made of high-purity graphite coated with a SiC film resistant to high-temperature hydrogen.

  On the other hand, as described above, it is important for the wafer to have a uniform temperature distribution in the surface to make the doping concentration uniform. As a method for making the temperature distribution on the wafer uniform, a high-frequency coil is used. A CVD apparatus having a SiC substrate mounting susceptor made of a graphite block, a film forming method using this CVD apparatus, and a semiconductor device manufactured by this film forming method are known in a water-cooled double vacuum quartz tube wound with (Patent Document 1).

  In addition, a chemical substrate including a reaction chamber of a semiconductor substrate in which a plurality of silicon substrates are placed and an epitaxial silicon film is formed on the surface of the silicon substrate, and a substrate heating source including an electromagnetic generator in the reaction chamber. There is a description regarding performing a film formation with few defects by heating a silicon substrate uniformly in a short time by using a phase growth apparatus (CVD apparatus) (Patent Document 2). There is a description related to forming a SiC film by placing a plurality of SiC crystal substrates on different surfaces of a susceptor (Patent Document 3).

An SiC epitaxial film forming apparatus that improves the temperature distribution in the wafer surface by providing an insulating heat shield downstream of the gas is known (Patent Document 4).
JP 2003-86516 A JP 2001-308014 A JP 2002-164294 A JP 2005-5503 A

  However, in recent years, with the development and expansion of SiC semiconductor devices, there has been a demand for reduction in the price. For this reason, processing of a large number of wafers (increasing the number of wafers in one batch) is strongly demanded in order to increase the area of SiC wafers and reduce production costs. In order to make this possible, a large-diameter and large-capacity film forming apparatus capable of processing a large-area wafer is necessary, but there is a problem that the conventional film forming apparatus is difficult to cope with.

  In other words, conventionally, large-area furnace barrel-type and pancake-type furnaces have been known for increasing the area and capacity, but these furnaces have been described above for the purpose of improving the uniformity of temperature distribution. In the case of a hot wall structure, since it is necessary to surround the periphery of the wafer with a heating element, the apparatus becomes very large and the gas flow rate that needs to flow tends to increase too much. Furthermore, since the susceptor for supporting the wafer becomes large, there is a problem that the heat capacity increases, the controllability with respect to temperature decreases, and the life of the susceptor coating decreases due to an increase in temperature difference between the wafer and the susceptor. It was difficult to do.

  Further, even in the case of the conventional hot wall structure of FIG. 2, when the large diameter structure is adopted, the reaction gas 27 is almost heated under reduced pressure only by heat conduction due to contact with the hot wall 22. Although the reaction gas flowing in the vicinity of the wall surface 22 becomes high temperature, the reaction gas 27 flowing away from the wall surface of the hot wall 22 tends to remain at a low temperature. In addition, since the inside of the pipe is at a low pressure, the heat conduction of the reaction gas is also poor. As a result, the temperature distribution of the reaction gas occurs in the radial direction of the hot wall 22, and the uniformity of the doping concentration of the epitaxial film is deteriorated. This tendency increases as the diameter of the hot wall 22 is increased. That is, in the large-area SiC wafer, improvement of the uniformity of the doping concentration distribution remains as one of the important issues to be solved.

In addition, regarding the homogenization of the wafer temperature distribution described in Patent Document 4, the heat shield is an insulating member disposed downstream of the gas and contributes to the improvement of the wafer temperature distribution, but the reaction gas temperature is made uniform. The problem is that is not very effective.
The present invention has been made in view of the above-described problems, and the object of the present invention is to solve the above-mentioned problems, and even if the hot wall has a large diameter and the SiC substrate has a large area, Provided is a method for manufacturing a semiconductor SiC substrate with an epitaxial SiC film and an epitaxial SiC film forming apparatus capable of making the temperature distribution in the wall uniform and making the doping concentration distribution of the epitaxial SiC film formed on the SiC substrate uniform. That is.

  According to the first aspect of the present invention, the first hot wall and the second hot wall are disposed in the heat-resistant cylindrical tube having the reaction gas inlet and the outlet at both ends and capable of being depressurized via the heat insulating material. A support member that is arranged side by side in the axial direction of the heat-resistant cylindrical tube and that attaches a SiC crystal substrate in a reaction chamber space provided in the first hot wall is disposed, and the heat-resistant cylindrical tube at a position facing the first hot wall is arranged. An induction heating device for inductively heating the first hot wall is provided on the outer periphery, and the second hot wall is a gas flow path provided in a direction parallel to the axis of the heat-resistant cylindrical tube, and has one end Is connected to the reaction gas inlet and rectifies the inflowing reaction gas, and the other end is an epitaxial SiC film forming apparatus having a gas flow path leading to the reaction chamber space in the first hot wall. And, the object of the present invention can be achieved.

According to the invention described in claim 2, it is preferable that the heat-resistant cylindrical tube is an epitaxial SiC film forming apparatus according to claim 1, wherein the heat-resistant cylindrical tube is a quartz tube.
According to the invention of claim 3, the support member to which the first hot wall, the second hot wall, and the SiC crystal substrate are attached is mainly composed of graphite. 2 is more preferable.

According to the invention of claim 4, the SiC film is coated on the surface of the support member to which the first hot wall, the second hot wall, and the SiC crystal substrate are attached. It is desirable to use the epitaxial SiC film forming apparatus according to any one of Items 1 to 3.
According to the invention described in claim 5, the support member to which the SiC crystal substrate is attached has a substrate support inclined surface facing the inflow direction of the reaction gas in the second hot wall. More preferably, the epitaxial SiC film forming apparatus according to any one of claims 1 to 4 is used.

  According to the invention of claim 6, the number of gas flow paths in the second hot wall is more than one and not more than three, and the cross-sectional area of the gas flow paths is combined. The epitaxial SiC film forming apparatus according to any one of claims 1 to 5, wherein a ratio to a gas flow path cross-sectional area in the first hot wall is more than 1/6 and not more than 1/2. Is more preferable.

  According to the seventh aspect of the present invention, using the epitaxial SiC film forming apparatus according to any one of the first to sixth aspects, the support substrate in the film forming apparatus is used. The object of the present invention is achieved by providing a method of manufacturing a SiC semiconductor substrate with an epitaxial SiC film in which a SiC crystal substrate is placed on the SiC crystal substrate and an SiC epitaxial film is formed on the SiC crystal substrate.

  According to the invention of claim 8, the heat-resistant pipe has the hot wall and the inflow side and the discharge side heat retaining members in the shape of closing the openings at both ends of the hot wall through the heat insulating material, respectively. , A SiC crystal substrate support member disposed in a space formed by the hot wall and both the inflow side and the outflow side heat retaining members, and fitted to both ends of the heat-resistant tube, respectively, and a gas inlet and a gas, respectively. Epitaxial SiC film forming apparatus comprising: a terminal jig that has a discharge port and enables the opening of both ends of the heat-resistant tube to be closed; and an induction heating coil provided on the outer periphery of the heat-resistant tube facing the position of the hot wall The inflow-side heat retaining member is a gas flow path provided in a direction parallel to the axis of the heat-resistant tube, and has one end connected to the reaction gas inlet and rectifies the inflowing reaction gas. Said An object of the present invention is to provide an epitaxial SiC film forming apparatus that includes a gas flow path that leads to the space in the wall, and the discharge-side heat retaining member includes a flow path for exhaust gas having a shape that allows passage of the SiC crystal substrate. Achieved.

According to the ninth aspect of the present invention, the epitaxial SiC film forming apparatus according to the eighth aspect of the present invention is preferably such that the heat-resistant tube is a quartz tube.
According to the invention of claim 10, the hot wall, the heat retaining member, and the support member on which the SiC crystal substrate is placed are each composed mainly of graphite. Or it is more preferable to use the epitaxial SiC film forming apparatus described in 9.

  According to the invention of claim 11, the SiC film is coated on the surface of the support member on which the hot wall, the heat retaining member, and the SiC crystal substrate are placed. The epitaxial SiC film forming apparatus according to any one of 8 to 10 is desirable.

  According to the present invention, even if the hot wall is enlarged to increase the area of the SiC substrate, the temperature distribution in the hot wall is made uniform and the doping concentration distribution of the epitaxial SiC film formed on the SiC substrate is made uniform. The manufacturing method of the semiconductor SiC substrate with an epitaxial SiC film and the epitaxial SiC film-forming apparatus which can be provided can be provided.

Hereinafter, a method for manufacturing a semiconductor SiC substrate with an epitaxial SiC film and an epitaxial SiC film forming apparatus according to the present invention will be described in detail with reference to the drawings. The present invention is not limited only to the description of the examples described below unless the gist of the present invention is exceeded.
FIG. 1 is a sectional view of an essential part of an epitaxial SiC film forming apparatus according to the present invention. FIG. 6 is an axial cross-sectional view of the second hot wall according to the present invention. FIG. 7 is a cross-sectional view of an essential part of a different epitaxial SiC film forming apparatus according to the present invention. FIG. 8 is a reaction gas temperature distribution diagram in the radial direction in the heating part of the quartz tube. FIG. 9 is a schematic cross-sectional view of an epitaxial film forming apparatus according to Example 4 of the present invention. 10 is a cross-sectional view taken along line BB, line AA, and line CC in FIG. FIG. 11 is an inner wall temperature distribution diagram in the axial direction of the hot wall. FIG. 12 is a schematic sectional view of an epitaxial film forming apparatus according to Example 5 of the present invention.

  FIG. 1 is a schematic cross-sectional view of a hot wall furnace 10 according to the epitaxial SiC film forming apparatus of the present invention. Similar to the configuration of the conventional film forming apparatus shown in FIG. 2, the first hot wall 2 having a configuration in which a susceptor 3 for attaching a wafer 4 is disposed in the reaction chamber space 2-1 inside the quartz tube 1, and the quartz Between the gas introduction part (not shown) where the reaction gas 8 inflow port of the tube 1 is located, the second hot wall 7 mainly composed of graphite, which is characteristic in the first embodiment, is disposed. The second hot wall 7 includes three narrow gas flow paths 9 having an area equal to 1/6 of the cross-sectional area of the flow path (reaction chamber space) 2-1 in the first hot wall 2 per flow path. The flow path space is provided with an interval parallel to the axial direction. Accordingly, the gas channel total cross-sectional area of the second hot wall 7 / the gas channel cross-sectional area ratio of the first hot wall (gas channel cross-sectional area ratio) is 3 times 1/6 and is 1/2. . The length of the gas flow path 9 of the second hot wall 7 is ¼ of the entire length of the first hot wall 2.

  With the hot wall structure of Example 1, the results of thermal fluid analysis at 10 slm hydrogen, the first hot wall 2 central furnace wall temperature 1600 ° C., and the internal pressure 80 Torr, and the heat in the conventional hot wall structure shown in FIG. When the fluid analysis results are compared, the second hot wall 7 of Example 1 has both the rectification of the inflowing reaction gas 8 and the effect of preheating the reaction gas 8, and the gas in the radial direction and the gas flow direction. It was found that the temperature distribution was uniform. As a result, in the structure having the first hot wall 2 and the second hot wall 7 of the present invention as compared with the conventional hot wall structure, the region of the reaction chamber space 2-1 in the first hot wall 2 where the gas temperature is high. It has been found that a large area wafer can be processed. Specifically, on the basis of the region where the gas temperature is 1600 ° C., the region where the temperature difference from that region is within 100 ° C. (that is, 1500 ° C. or more) has spread 1.5 times. As a result, the variation in the in-plane doping concentration of the 3-inch wafer was 50% in the conventional film forming apparatus, but decreased to 10% in the film forming apparatus of the present invention, and the in-plane uniform doping concentration of the 3-inch wafer was reduced. Can be improved.

  On the other hand, regarding the hot wall comparative structure 1 that is one of the three gas flow paths 9 of the second hot wall 7 shown in FIG. When the gas temperature distribution in the hot wall was examined by analysis, the high temperature region of the gas temperature was slightly widened due to the preheating effect as compared with the conventional hot wall structure. Since the cross-sectional area is small (1/2 is reduced to 1/3, 1/6), the flow rate is increased, the gas cannot be fully heated, and the reaction gas temperature is higher than that of the hot wall structure having the three flow paths. It turned out that it fell. When the gas flow rate is lowered, the tendency of the reaction gas 8 temperature to decrease is certainly weakened, but instead, the residence time of the reaction gas 8 in the furnace is increased, and the replacement with the new inflow reaction gas is reduced, and monosilane, propane, etc. Since the reaction gas species are likely to be depleted and the film thickness distribution / concentration distribution may be deteriorated, the gas flow rate cannot be reduced. Furthermore, since the rectifying effect is not sufficient as compared with the case where the gas flow path 9 is three, the reaction gas 8 blown out from the gas flow path port concentrated in one central portion spreads in the radial direction and becomes a uniform gas distribution. In addition, a certain distance is required. When the gas flow velocity distribution was compared by the fluid analysis of the structure for comparison of one gas channel hot wall and the structure of three gas channels according to the present invention, the structure for comparison of one gas channel was three of the present invention. It was found that an extra distance of about 5 times was required for the gas to spread in the radial direction compared to the gas. This leads to an increase in the hot wall diameter and requires a useless member. For the above reasons, it has been found that it is more advantageous to provide a plurality of gas flow paths in order to make the reaction gas temperature uniform.

  The number of gas flow paths 9 of the second hot wall 7 is preferably as much as possible. However, if this gas flow path space is opened too much, the space ratio increases, the heat capacity of the second hot wall 7 decreases, and the gas flow is reversed by the gas. This is not preferable because the preheating effect is diminished. On the contrary, if the space of the gas flow path 9 is too small, the rectifying effect is reduced as described above, which is not preferable. Therefore, the gas channel cross-sectional area ratio exceeds 1/6 and is preferably 1/2 or less.

  The smaller the cross-sectional area of each gas flow path, the greater the heat exchange between the gas and the furnace wall, and the higher the gas temperature. Therefore, it is preferable that the particle size is small enough not to be clogged with particles in the reaction gas. Further, in order to obtain a sufficient rectifying effect, it is important to equalize each of the plurality of gas flow path cross-sectional areas. When the cross-sectional areas are different, the gas flows unevenly in the large area gas flow path, and a uniform gas flow in the radial direction cannot be obtained.

  Furthermore, the gas flow path length of the second hot wall 7 is also an important parameter. A comparative structure in which the gas flow path length of the second hot wall 7 was reduced to 1/10 of the gas flow path length of the hot wall structure according to the present invention was analyzed by thermofluid analysis. As a result, it was found that the radial distribution of the gas temperature is improved, but a sufficient preheating effect cannot be obtained. As a result, the temperature distribution in the gas flow direction is worse than that of the second hot wall structure having the gas flow path length according to the present invention. As the thickness (in the gas flow direction) of the second hot wall 7 increases, the gas temperature increases. However, if a uniform temperature distribution is obtained in the gas flow direction, the thickness beyond that is useless. This not only increases the furnace size but also undesirably increases the heat capacity of the second hot wall 7 and makes heating difficult.

  FIG. 6 shows an axial cross-sectional view of the second hot wall 37 according to the hot wall film forming apparatus of Example 2 in which the shape of the gas channel of the second hot wall is different. FIG. 6 is a cross-sectional view of the second hot wall 37 cut along the axial direction (gas flow direction) so that the cross section of the gas channel appears. In order to actively exchange heat between the furnace wall of the second hot wall 37 and the reaction gas 38, the gas flow path 39 has a meandering shape. As a result, it is possible to shorten the entire length of the second hot wall 37 without shortening the gas flow path 39, which saves space and reduces the heat capacity, which is advantageous in terms of ease of heating. .

  FIG. 7 shows a schematic cross-sectional view of a hot wall film forming apparatus 40 according to the third embodiment. (A) is a cross-sectional view of an axial direction, (b) is a longitudinal cross-sectional view in the center of (a). Unlike the above-described hot wall furnaces of the first and second embodiments, the gas flow in the inside of the first and second embodiments, which should be arranged with the first hot wall 42 via the heat insulating material 46 in the quartz tube 41. There is no second hot wall with a path. Instead, in the hot wall of the third embodiment, a plurality of susceptors (support members for attaching the SiC wafer) 43 for combining the function of the gas flow path and the support function of the SiC wafer 44 are provided in the first hot wall 42. The reaction chamber space 47 is characterized by being stacked in the height direction at intervals in parallel to each other.

  FIG. 8 is a reaction gas temperature distribution diagram showing the reaction gas temperature distribution in the radial direction in the heating section of the quartz tube, with the horizontal axis representing the tube diameter direction with the axis being 0, and the vertical axis representing the reaction gas temperature. In the temperature distribution of the reaction gas in the radial direction of the quartz tube 41 when hydrogen is allowed to flow through the hot wall 42 of Example 3 at about 10 liters / minute and heated to 1600 ° C., as shown in FIG. This shows that the gas has a temperature distribution in which the temperature of the gas rapidly increases in the vicinity of the inner wall surface of the hot wall 42 due to contact with the hot wall 42. It was found that a region 48 having a stable gas temperature, which is obtained by heat conduction and diffusion, exists in a space centered on the axial center away from the wall surface of the hot wall 42. In the third embodiment, the temperature stable region 48 is used to enable simultaneous processing of a plurality of sheets. Since the gas temperature is uniform, the doping variation between wafers can be kept small.

When the temperature distribution analysis of the reaction chamber space 47 when the number of the susceptors 43 shown in FIG. 7 is seven, the in-plane temperature of the susceptor 43 is almost uniformly heated in the range of 1550 ° C. to 1580 ° C. all right.
Next, when the flow rate distribution of hydrogen gas in the case of seven susceptors 43 was examined, the flow rate would change if the spacing between the stacked susceptors was different, so the spacing in the height direction of the susceptors 43 should be made uniform. I found out that

  The susceptor 43 was a SiC polycrystalline plate having a thickness of 500 μm. The susceptor 43 made of SiC polycrystal has corrosion resistance against high-temperature hydrogen and has a radiation rate as high as that of graphite. Therefore, the susceptor 43 easily absorbs radiant heat from a hot wall and is easily heated. Further, since the volume is small, the heat capacity is almost as small as that of the wafer, and the temperature difference between the wafer and the susceptor is small enough to be ignored.

  On the other hand, in the conventional hot wall, the heat capacity of the hot wall is extremely large compared to the wafer, and the contact between the wafer and the hot wall is not perfect due to the warpage of the wafer. A temperature difference is created between the hot wall and the wafer. In other words, the wafer is cooled by a cold gas, whereas the hot wall has a large heat capacity and remains hot. Due to this temperature difference, the problem of sublimating the coating on the hot wall wall and causing the coating to adhere to the back surface of the wafer may occur.

  Further, as another effect obtained by the hot wall structure of Example 3, the following can be mentioned. In the conventional hot wall, the gas flow stays in the vicinity of the furnace wall, and particles generated on the furnace wall do not flow.Therefore, when the wafer is in close contact with the furnace wall, the particles generated by the reaction gas adhere to the wafer. The problem that it is easy to occur. Since particles reduce the yield rate of devices, particle adhesion should be avoided as much as possible. In the present invention, the adhesion of particles can be reduced by using a susceptor to hold the wafer away from the furnace wall.

Furthermore, when the hot wall of Example 3 is used, a measure for relaxing heat transfer is provided at the contact portion 49 between the susceptor 43 and the hot wall 42 marked with a circle in the hot wall film forming apparatus shown in FIG. Is more desirable. Hereinafter, the contact portion will be specifically described with reference to FIGS.
FIG. 3 shows a cross-sectional view of the contact portion 1 having the structure of the contact portion 49 of the susceptor 43 and the hot wall 42. 4 and 5 are cross-sectional views of the contact portion 2 and the contact portion 3, respectively, of the improved structure. The contact portion 1 in FIG. 3 has a function of suppressing heat transfer by reducing the surface contact between the susceptor 43 and the hot wall 42. The contact portion 2 in FIG. 4 has a function of suppressing heat transfer by bringing the contact portion between the susceptor 43 and the hot wall 42 into line contact by inclining the contact portion on the hot wall side. The contact portion 3 in FIG. 5 further has a function of suppressing heat transfer by sharpening the contact portion on the hot wall side to enhance the cooling effect by the surrounding gas. Table 1 below shows the measurement results of the temperature difference between the contact portions 1, 2, and 3 of the contact portions. According to Table 1, it can be seen that both the structures of FIG. 4 and FIG. 5 are more preferable because the temperature difference is improved as compared with FIG.

なお、本発明にかかるホットウォールは横型であることが望ましい。なぜならば、石英間を縦に配置した縦型ホットウォールでは、重力で落下しようとするウエハをサセプタ上に配置するため、サセプタ上にネジやスリットなどの保持部品もしくはサセプタを楔形にする必要があり、サセプタを大型化してしまうので、空間の利用効率が低下する。これは多数枚同時処理には適切ではない。

The hot wall according to the present invention is preferably a horizontal type. This is because in a vertical hot wall in which quartz is vertically arranged, a wafer to be dropped due to gravity is placed on the susceptor, so that holding parts such as screws and slits or the susceptor must be wedged on the susceptor. Since the susceptor is enlarged, the space utilization efficiency is lowered. This is not suitable for simultaneous processing of a large number of sheets.

  FIG. 9 shows a sectional view of an epitaxial film forming apparatus according to Example 4 of the present invention. This film forming apparatus includes a quartz glass vapor phase reactor 50, a gas inlet 51, and a gas outlet 52. The outermost periphery of the quartz glass gas phase reactor 50 is a quartz glass tube 65. Since it is not drawn to an accurate scale in FIG. 9, the length of this quartz glass tube is only slightly longer than the length of the hot wall 55, but actually it is much longer and doubles. Is 5 times longer. A stainless steel end jig 63 having a gas inlet 51 and a gas outlet 52 is attached to both ends of the quartz glass tube. In particular, an opening / closing mechanism 64 is provided at the end on the gas outlet side so that a wafer can be taken in and out. Arranged in the reaction furnace 50 are a susceptor 53 made of graphite or SiC-coated graphite, a hot wall 54 made of graphite or SiC-coated graphite, a heat insulating material 55, a gas inflow side heat retaining member 56, a gas discharge side heat retaining member 57, and the like. Has been.

A counterbore (not shown) is provided at the center of the susceptor 53, and the SiC wafer 58 is placed at a fixed position. The diameter of the SiC wafer 58 is 3 inches on the current mass production base, but if the diameter increases, the diameter of the quartz glass gas phase reactor will be increased accordingly and 5 inches, 6 inches, etc. It is enough to correspond to the size of.
FIG. 10A shows a cross-sectional view taken along the line BB in a state where the SiC wafer 58 is placed on the susceptor 53. Both heat retaining members 56 and 57 are composed of a heating element 54 made of graphite or SiC-coated graphite and a heat insulating material 55 surrounding the heating element 54, and are arranged at gas inlets and outlets at both ends of the hot wall. As shown in the cross-sectional views of FIGS. 10B and 10C, a plurality of gas ventilation holes 61 for gas ventilation are opened in both the heat retaining members 56 and 57 so that the reaction gas can enter and exit. . Although the shape of the vent hole 61 of the gas inflow side heat retaining member 56 is arbitrary, the vent hole 62 of the gas exhaust side heat retaining member 57 is formed into a shape having a space where the wafer can be taken out when the SiC wafer 58 is replaced.

  The susceptor 53 is heated by inductively heating the hot wall 55 by a high frequency coil 59 for heating disposed around the outer periphery of the quartz tube around the reaction furnace 50 and transferring heat therefrom. The temperature of the susceptor 53 is monitored by a pyrometer 60 provided outside the reaction furnace 50, and the temperature is controlled by the output of the heating high frequency coil 59. Both the heat retaining members 56 and 57 are heated by induction heating and radiation from the hot wall, thereby preventing a temperature drop in the vicinity of the gas inlet / outlet of the inner wall of the hot wall as seen in a conventional reactor.

Comparison of the temperature distribution of the inner wall of the hot wall in the direction parallel to the gas flow (DD direction) using a thermocouple for a conventional hot wall without a heat retaining member (conventional furnace) and a hot wall having a heat retaining member as shown in FIG. The results are shown in FIG. In Example 4, it can be seen that the temperature at the end of the hot wall is higher than that in the conventional furnace.
In addition, the gas inflow side heat retaining member 56 has a gas preheating effect and a rectifying effect, and contributes to the uniformity of crystal quality, film thickness, and impurity concentration distribution by making the reaction gas temperature distribution in the hot wall uniform. The reaction gas temperature is made uniform because the reaction gas is heated when passing through the gas ventilation holes formed in the heat retaining member, and is rectified and made uniform by passing through the plurality of gas ventilation holes. The reaction gas is made of monosilane (SiH ₄ ), propane (C ₃ H ₈ ), and nitrogen (N ₂ ) in the case of n-type and trimethylaluminum (TMA) in the case of p-type using hydrogen as a carrier gas. It consists of mixed gas, is introduced from the gas inlet, becomes a rectified gas flow through the gas inflow side heat retaining member 56, flows parallel to the susceptor and the wafer surface, passes through the gas outlet side heat retaining member 57, and passes through the gas outlet. It is exhausted with a dry pump. The pressure inside the furnace is controlled by exhaust using a dry pump and a pressure regulating valve provided at the end of the gas discharge port. Actual film formation is performed under the following conditions.
Furnace pressure: 10 to 760 Torr
Carrier hydrogen flow rate: 1-100 SLM
SiH ₄ flow rate: 1-1000 sccm
C ₃ H ₈ flow rate: 1-1000 sccm
N ₂ flow rate: 0.001 to 1000 sccm
TMA (trimethylaluminum) flow rate: 0.000001-1 sccm
Wafer temperature: 1500 ° C. to 2000 ° C.
The above conditions may vary depending on the size of the device and the detailed structure inside. According to the fourth embodiment, in order to increase the diameter of the wafer, extra energy is required for heating, and it is necessary to increase the length of the hot wall, which is likely to deteriorate the temperature controllability. However, since it can be suppressed as compared with the prior art, the crystal quality, film thickness, and uniformity of impurity concentration of the SiC epitaxial film can be improved.

  In the fourth embodiment, the case where the present invention is applied to a hot wall type CVD furnace has been shown. In particular, when the particles coming from the heat insulating material do not like to adhere to the wafer, the temperature difference between the upper and lower sides of the wafer is further increased. In order to reduce the size, a structure in which the susceptor is floated in the central space inside the hot wall and the susceptor is heated by radiation from the hot wall is also preferable. FIG. 12A is a sectional view of the epitaxial film forming apparatus according to the fifth embodiment. The inflow / discharge heat retaining members 56 and 57 at both ends of the hot wall 70 in the fifth embodiment and the stainless steel end jigs 63 and 64 outside the hot wall 70 may have the same structure as in the fourth embodiment.

  In the fifth embodiment, as shown in FIG. 12, the structure in which the susceptor 73 is floated in the central space in the hot wall 70 and the SiC wafer 78 is placed thereon is different from that in the fourth embodiment. Since the structure is the same as that of No. 4, it is necessary to increase the diameter of the wafer and to increase the length of the hot wall, which requires extra energy for heating and the temperature controllability is likely to deteriorate. Even in this case, since the increase in length can be suppressed as compared with the conventional case, the temperature distribution of the inner wall of the hot wall 70 and the reaction gas temperature distribution in the hot wall 70 can be made more uniform, and the crystal quality, film thickness, impurity concentration of the epitaxial film can be achieved. Can improve the uniformity.

It is principal part sectional drawing of the hot wall concerning this invention. It is principal part sectional drawing of the conventional hot wall. It is an expanded sectional view of the contact part 1 of the susceptor-hot wall concerning Example 3. FIG. It is an expanded sectional view of the contact part 2 of the susceptor-hot wall concerning Example 3. FIG. 6 is an enlarged cross-sectional view of a contact portion 3 of a susceptor-hot wall according to Example 3. FIG. It is sectional drawing of the gas channel direction of the 2nd hot wall concerning Example 2. FIG. FIG. 6 is a cross-sectional view of a main part of a hot wall according to Example 3. FIG. 7 is a reaction gas temperature distribution diagram in the tube diameter direction of a hot wall according to Example 3. 6 is a schematic cross-sectional view of a film forming apparatus according to Example 4. FIG. It is each sectional drawing cut | disconnected by the AA, BB, CC line of the susceptor hot wall concerning the film-forming apparatus of FIG. It is an inner-wall temperature distribution figure in the DD direction of the conventional thing and the hot wall concerning Example 4. FIG. 6 is a schematic cross-sectional view of a film forming apparatus according to Example 5. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Quartz tube 2 ... 1st hot wall 3 ... Susceptor 4 ... SiC crystal substrate, wafer, SiC wafer 5 ... High frequency coil 6 ... Heat insulating material 7 ... 2nd hot wall 8 ... Reaction gas 9 ... Gas flow path 10 ... Hot wall Reactor

Claims (11)

A first hot wall and a second hot wall are arranged in the axial direction of the heat-resistant cylindrical tube through a heat insulating material in a heat-resistant cylindrical tube having a reaction gas inlet and a discharge port at both ends and capable of being depressurized. A support member for attaching a SiC crystal substrate is disposed in a reaction chamber space provided in the wall, and induction heating for inductively heating the first hot wall on the outer periphery of the heat-resistant cylindrical tube at a position facing the first hot wall An apparatus is provided, and the second hot wall is a gas flow path provided in a direction parallel to the axis of the heat-resistant cylindrical tube, one end of which is connected to the reaction gas inlet and rectifies the inflowing reaction gas An epitaxial SiC film forming apparatus, wherein the other end is provided with a gas flow path leading to the space in the first hot wall. 2. The epitaxial SiC film forming apparatus according to claim 1, wherein the heat-resistant cylindrical tube is a quartz tube. The epitaxial SiC film-forming apparatus according to claim 1 or 2, wherein a supporting member for attaching the first hot wall, the second hot wall, and the SiC crystal substrate contains graphite as a main component. 4. The epitaxial SiC composition according to claim 1, wherein a SiC film is coated on a surface of a support member to which the first hot wall, the second hot wall, and the SiC crystal substrate are attached. Membrane device. 5. The epitaxial SiC according to claim 1, wherein the support member to which the SiC crystal substrate is attached has a substrate support inclined surface facing the inflow direction of the reaction gas in the second hot wall. Deposition device. The number of gas passages in the second hot wall is more than one and not more than three, and the ratio of the sectional area of the gas passages combined with the sectional area of the gas passages in the first hot wall is 6. The epitaxial SiC film forming apparatus according to claim 1, wherein the epitaxial SiC film forming apparatus is more than 1/6 and not more than 1/2. Using the epitaxial SiC film forming apparatus according to any one of claims 1 to 6, a SiC crystal substrate is placed on a support member in the film forming apparatus, and an SiC epitaxial film is formed on the SiC crystal substrate. A method of manufacturing a SiC semiconductor device with an epitaxial SiC film, comprising forming a film. In the heat-resistant pipe, a hot wall and an inflow side and an exhaust side heat retaining member configured to block the openings at both ends of the hot wall via a heat insulating material, respectively, the hot wall, both the inflow side and the exhaust side heat retaining member The SiC crystal substrate support member disposed inside the space formed from the two ends of the heat-resistant tube, fitted with both ends of the heat-resistant tube, each having a gas inlet and a gas outlet, and closed pipes at both ends of the heat-resistant tube. An epitaxial SiC film forming apparatus comprising: a terminal jig to be enabled; and an induction heating coil provided on an outer periphery of the heat-resistant tube facing the position of the hot wall, wherein the inflow-side heat retaining member is disposed inside the shaft of the heat-resistant tube Gas flow path provided in a direction parallel to the gas flow path, one end of which is connected to the reaction gas inlet and rectifies the inflowing reaction gas, and the other end is a gas flow path leading to the space in the hot wall. For example, the discharge-side heat insulating member epitaxial SiC film forming apparatus characterized by comprising an exhaust gas passage of the passable shape of SiC crystal substrate. 9. The epitaxial SiC film forming apparatus according to claim 8, wherein the heat-resistant tube is a quartz tube. 10. The epitaxial SiC film forming apparatus according to claim 8, wherein the hot wall, the heat retaining member, and the supporting member on which the SiC crystal substrate is placed mainly comprise graphite. 11. The epitaxial SiC film formation according to any one of claims 8 to 10, wherein a SiC film is coated on a surface of a support member on which the hot wall, the heat retaining member, and the SiC crystal substrate are placed. apparatus.

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