JP2014123617A - Manufacturing method and manufacturing apparatus of silicon carbide substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method and a manufacturing apparatus of a silicon carbide substrate which can efficiently manufacture a silicon carbide substrate excellent in uniformity of an impurity concentration and excellent in crystallinity.SOLUTION: A silicon carbide substrate manufacturing method comprises: a process of preparing a base substrate 10 composed of a silicon carbide; and a process of forming an epitaxially grown film on the base substrate 10. In the process of forming the epitaxially grown film, the base substrate 10 is heated in a state where a reaction gas G3 obtained by mixture of a first gas G1 containing NHand a second gas G2 containing HCl and without containing NHis supplied toward the base substrate 10. The first gas G1 is mixed with the second gas G2 after being heated to a decomposition temperature of NH.

Description

  The present invention relates to a method and an apparatus for manufacturing a silicon carbide substrate, and more specifically, a silicon carbide substrate capable of efficiently manufacturing a silicon carbide substrate having excellent impurity concentration uniformity and crystallinity. The present invention relates to a manufacturing method and a manufacturing apparatus.

  In recent years, in order to enable a semiconductor device to have a high breakdown voltage and low loss, silicon carbide has been adopted as a material constituting the semiconductor device. Silicon carbide is a wide band gap semiconductor having a larger band gap than silicon that has been widely used as a material constituting a semiconductor device. Therefore, by adopting silicon carbide as a material constituting the semiconductor device, it is possible to achieve a high breakdown voltage and a low on-resistance of the semiconductor device. In addition, a semiconductor device that employs silicon carbide as a material has an advantage that a decrease in characteristics when used in a high temperature environment is small as compared with a semiconductor device that employs silicon as a material.

  A silicon carbide substrate used in such a semiconductor device is manufactured, for example, by forming an epitaxial growth film on a base substrate made of silicon carbide. Specifically, a silicon carbide substrate having an epitaxial growth film formed on a base substrate is manufactured by thermally decomposing and reacting a source gas such as silane or propane and a dopant gas such as nitrogen. In addition, in order to manufacture a higher-quality semiconductor device with high efficiency, a method and apparatus for manufacturing a silicon carbide substrate with excellent impurity concentration uniformity and crystallinity with high efficiency is required. For example, Japanese Patent Laying-Open No. 2006-261612 (hereinafter referred to as Patent Document 1) discloses a method for manufacturing a silicon carbide semiconductor capable of making the nitrogen concentration uniform in the substrate surface. Also, for example, F.A. La Via et al, “High growth rate process in a SiC horizontal CVD reactor using HCl”, MICRO ELECTRONIC ENGINEERING, January 2006, Volume 83, Issue 1, p. 48-50 (hereinafter referred to as Non-Patent Document 1) discloses that the epitaxial growth rate is improved by forming an epitaxial growth film using a reaction gas containing hydrogen chloride.

JP 2006-261612 A

F. La Via et al, “High growth rate process in a SiC horizontal CVD reactor using HCl”, MICRO ELECTRONIC ENGINEERING, January 2006, Volume 83, Issue 1, p. 48-50

  When an epitaxially grown film is formed on the base substrate, if ammonia, which is easier to thermally decompose, is used as the dopant gas instead of nitrogen, the impurity concentration in the substrate surface can be made more uniform. Further, as disclosed in Non-Patent Document 1, when an epitaxial growth film is formed using a reaction gas containing hydrogen chloride, the growth rate can be improved, so that a silicon carbide substrate can be manufactured more efficiently. can do. However, when ammonia is used as a dopant gas and epitaxial growth is performed using a reaction gas containing hydrogen chloride, a silicon carbide substrate with a uniform impurity concentration can be efficiently produced, while carbonization is performed. There was a problem that the crystallinity of the silicon substrate was lowered.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a silicon carbide substrate manufacturing method and a manufacturing method capable of efficiently manufacturing a silicon carbide substrate having excellent impurity concentration uniformity and crystallinity. Is to provide a device.

  A method for manufacturing a silicon carbide substrate according to the present invention includes a step of preparing a base substrate made of silicon carbide and a step of forming an epitaxial growth film on the base substrate. In the step of forming the epitaxial growth film, the base substrate is heated in a state where a reaction gas in which a first gas containing ammonia and a second gas containing hydrogen chloride and not containing ammonia are supplied to the base substrate. . The first gas is heated to the thermal decomposition temperature of ammonia and then mixed with the second gas.

  The present inventor has made a detailed study on the cause of the decrease in crystallinity of the silicon carbide substrate when ammonia is used as a dopant gas and epitaxial growth is performed using a reaction gas containing hydrogen chloride. As a result, when ammonia and hydrogen chloride are mixed before pyrolysis, they react to produce a solid by-product, and the by-product adheres to the growing epitaxial film as a foreign substance. As a result, the present invention was conceived.

  In the method for manufacturing a silicon carbide substrate according to the present invention, a reaction gas containing ammonia that is easily pyrolyzed is used, so that a silicon carbide substrate having a more uniform impurity (nitrogen atom) concentration can be manufactured. Further, in the method for manufacturing the silicon carbide substrate, since a reactive gas containing hydrogen chloride is used, the speed of epitaxial growth can be improved. Further, in the method for manufacturing the silicon carbide substrate, the first gas containing ammonia is heated to the thermal decomposition temperature of ammonia and then mixed with the second gas containing hydrogen chloride to form a reaction gas. Therefore, it can suppress that ammonia in 1st gas and hydrogen chloride in 2nd gas react before thermal decomposition, and produce | generate a solid by-product (ammonium chloride). Thereby, it can suppress that the said by-product adheres to the growing epitaxial film, and the crystallinity of a silicon carbide substrate falls. Therefore, according to the method for manufacturing a silicon carbide substrate according to the present invention, a silicon carbide substrate having excellent impurity concentration uniformity and crystallinity can be efficiently manufactured.

  In the silicon carbide substrate manufacturing method, in the step of forming an epitaxially grown film, the base substrate may be heated while being disposed inside the reaction tube. The first gas may be mixed with the second gas outside the reaction tube. More specifically, the first gas may be mixed with the second gas after being heated to the thermal decomposition temperature by a preheating unit disposed outside the reaction tube.

  Thereby, the reaction gas in which the first gas and the second gas are more uniformly mixed can be supplied toward the base substrate. As a result, a higher quality silicon carbide substrate can be manufactured.

  In the silicon carbide substrate manufacturing method, in the step of forming an epitaxially grown film, the base substrate may be heated while being disposed inside the reaction tube. The first gas may be mixed with the second gas inside the reaction tube. More specifically, the first gas may be mixed with the second gas after being heated to the thermal decomposition temperature by a heating unit for heating the base substrate.

  Thereby, a mechanism for heating the first gas to the thermal decomposition temperature, which is different from the mechanism for heating the base substrate, can be omitted. As a result, the configuration of the apparatus used for manufacturing the silicon carbide substrate can be further simplified.

  An apparatus for manufacturing a silicon carbide substrate according to the present invention forms a reaction tube for arranging a base substrate made of silicon carbide therein, a heating unit for heating the base substrate, and an epitaxially grown film on the base substrate. And a gas supply unit for supplying the reaction gas to the inside of the reaction tube. The gas supply unit is configured to be able to supply a reaction gas in which a first gas containing ammonia and a second gas containing hydrogen chloride and not ammonia are mixed into the reaction tube. The gas supply unit is configured to be capable of mixing with the second gas after heating the first gas to the thermal decomposition temperature of ammonia.

  The silicon carbide substrate manufacturing apparatus according to the present invention can supply a reaction gas containing ammonia, which is easily pyrolyzed, into the reaction tube, so that the impurity (nitrogen atom) concentration is made more uniform. A silicon substrate can be manufactured. Moreover, since the said manufacturing apparatus of a silicon carbide substrate can supply the reaction gas containing hydrogen chloride to the inside of a reaction tube, it can improve the speed | rate of epitaxial growth. Furthermore, the silicon carbide substrate manufacturing apparatus can form a mixed gas by heating the first gas containing ammonia to the thermal decomposition temperature of ammonia and then mixing with the second gas containing hydrogen chloride. Yes. Therefore, it can suppress that ammonia in 1st gas and hydrogen chloride in 2nd gas react before thermal decomposition, and produce | generate a solid by-product (ammonium chloride). Thereby, it can suppress that the said by-product adheres to the growing epitaxial film, and the crystallinity of a silicon carbide substrate falls. Therefore, the silicon carbide substrate manufacturing apparatus according to the present invention can efficiently manufacture a silicon carbide substrate having excellent impurity concentration uniformity and crystallinity.

  In the silicon carbide substrate manufacturing apparatus, the gas supply unit may be disposed outside the reaction tube, and may include a preheating unit for heating the first gas to the thermal decomposition temperature.

  Thereby, the reaction gas in which the first gas and the second gas are mixed more uniformly can be supplied toward the base substrate disposed inside the reaction tube. As a result, a higher quality silicon carbide substrate can be manufactured.

  In the silicon carbide substrate manufacturing apparatus, the gas supply unit has a portion located inside the reaction tube, and reacts the first gas pipe for supplying the first gas into the reaction tube and the second gas. And a second gas pipe for supplying the inside of the pipe.

  Accordingly, the first gas can be heated to the above pyrolysis temperature inside the reaction tube and can be mixed with the second gas after the heating. As a result, it is not necessary to separately provide a mechanism for heating the first gas to the thermal decomposition temperature separately from the heating unit for heating the base substrate, and the apparatus configuration can be further simplified.

  As is apparent from the above description, according to the method and apparatus for manufacturing a silicon carbide substrate according to the present invention, it is possible to efficiently manufacture a silicon carbide substrate having excellent impurity concentration uniformity and crystallinity. A method and apparatus for manufacturing a silicon carbide substrate can be provided.

It is a schematic sectional drawing which shows the structure of the manufacturing apparatus of a silicon carbide substrate. 3 is a flowchart schematically showing a method for manufacturing a silicon carbide substrate. It is the schematic for demonstrating the manufacturing method of a silicon carbide substrate. It is the schematic for demonstrating the manufacturing method of a silicon carbide substrate. FIG. 6 is a schematic cross sectional view showing a configuration of a silicon carbide substrate manufacturing apparatus according to a second embodiment. FIG. 6 is a schematic top view showing an enlarged configuration of a silicon carbide substrate manufacturing apparatus according to a second embodiment. It is the schematic which expands and shows the structure of gas piping. It is the schematic which expands and shows the structure of other gas piping. FIG. 10 is a schematic cross sectional view showing a configuration of a silicon carbide substrate manufacturing apparatus according to a third embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
First, the structure of the silicon carbide substrate manufacturing apparatus according to the first embodiment which is an embodiment of the present invention will be described. Referring to FIG. 1, a CVD (Chemical Vapor Deposition) apparatus 1 which is a silicon carbide substrate manufacturing apparatus according to the present embodiment forms an epitaxially grown film on a base substrate 10 made of silicon carbide to form a silicon carbide substrate. It is an apparatus for manufacturing. The CVD apparatus 1 mainly includes a quartz tube 8 (reaction tube), an RF (Radio Frequency) coil 9 (heating unit), a heat insulating material 4, a heating element 5, a susceptor 6, and a gas supply unit 7. ing.

  The quartz tube 8 has a cylindrical shape, for example, and has a reaction chamber 8a for placing the base substrate 10 therein. The quartz tube 8 is configured such that a reaction gas for epitaxial growth is supplied into the reaction chamber 8a from one opening (left side in the figure), and the reaction gas is discharged from the other opening (right side in the figure). Has been.

  The RF coil 9 is a member for heating the reaction gas supplied into the base substrate 10 and the reaction chamber 8a. The RF coil 9 is disposed so as to be wound along the outer peripheral surface 8c of the quartz tube 8, and heats the heating element 5 disposed inside the quartz tube 8 by high frequency induction heating. More specifically, when a high frequency current is supplied from a power source (not shown) to the RF coil 9, magnetic lines of force that change around the RF coil 9 are generated, and an eddy current flows through the heating element 5 due to the change of the magnetic lines of force. And resistance heat | fever generate | occur | produces by an eddy current flowing, and the heat generating body 5 is heated. Thereby, the reaction gas supplied into the base substrate 10 and the quartz tube 8 arranged on the susceptor 6 can be heated.

  The heat insulating material 4 is a member for insulating the reaction chamber 8 a and the outside of the quartz tube 8, and is disposed along the inner peripheral surface 8 b of the quartz tube 8. The heat insulating material 4 is made of carbon, for example.

  The heating element 5 is made of a conductive material that can be heated by induction heating using the RF coil 9, and is made of, for example, carbon. The heating element 5 is disposed along the inner peripheral surface 4 a of the heat insulating material 4. For this reason, the quartz tube 8, the heat insulating material 4, and the heating element 5 are arranged in the order of the heating element 5, the heat insulating material 4, and the quartz tube 8 in the radial direction of the quartz tube 8 (the direction from the center to the outer periphery). It is in a state. Further, a concave portion 5b for arranging the susceptor 6 is formed in a portion including the inner peripheral surface 5a of the heating element 5.

  The susceptor 6 is a member for placing the base substrate 10 in contact therewith. The susceptor 6 is made of carbon, for example, and the surface thereof is coated with silicon carbide (SiC) or tantalum carbide (TaC). The susceptor 6 is disposed in a recess 5 b formed in a part of the heating element 5.

  The gas supply unit 7 is a member for supplying a reaction gas for forming an epitaxial growth film on the base substrate 10 into the quartz tube 8. The gas supply unit 7 mainly includes gas cylinders 71a to 71e, gas pipes 72a to 72c, and a preheating unit 73.

The gas cylinder 71a is filled with hydrogen (H ₂ ) gas which is a carrier gas. The gas cylinders 71b and 71c are filled with silane (SiH ₄ ) gas and propane (C ₃ H ₈ ) gas, respectively, which are raw materials for epitaxial growth of silicon carbide. The gas cylinder 71d is filled with hydrogen chloride (HCl) gas. The gas cylinder 71e is filled with ammonia (NH ₃ ) gas which is a dopant gas.

Each of the gas cylinders 71a to 71d is connected to a gas pipe 72b. Each of the gas filled in the gas cylinders 71a to 71d is supplied into the gas pipe 72b by opening and closing a valve (not shown) provided in each gas cylinder. The gas cylinder 71e is connected to the gas pipe 72a. The NH ₃ gas filled in the gas cylinder 71e is supplied to the preheating unit 73 through the gas pipe 72a.

The preheating unit 73 is disposed outside the quartz tube 8. In the preheating section 73, for example, the induction heating coil and the heating element (not shown) is provided, NH ₃ gas supplied through the gas pipe 72a (the first gas G1), the thermal decomposition temperature of the NH ₃ (800 To 1000 ° C. or lower).

The gas pipe 72 c has one end (left side in the figure) connected to the preheating unit 73 and the other end (right side in the figure) connected to the end of the quartz tube 8. The gas pipe 72c is connected to the gas pipe 72b. Thereby, the gas (second gas G2) containing H ₂ , SiH ₄ , C ₃ H ₈ and HCl but not NH ₃ is mixed with the first gas G1 at the connecting portion between the gas pipe 72b and the gas pipe 72c. It is possible to do. The reaction gas G3 in which the first gas G1 and the second gas G2 are mixed can be supplied into the quartz tube 8 through the gas pipe 72c.

As described above, CVD apparatus 1 according to the present embodiment includes quartz tube 8 for placing base substrate 10 made of silicon carbide therein, RF coil 9 for heating base substrate 10, and base substrate. A gas supply unit 7 for supplying a reaction gas G3 for forming an epitaxially grown film on the quartz tube 8 is provided. Then, the gas supply unit 7, a first gas G1 containing NH _3, comprises HCl, and the reaction gas G3 mixed with a second gas G2 containing no NH ₃ can be supplied into the quartz tube 8 It is configured. The gas supply unit 7 is configured to be able to mix the first gas G1 with the second gas G2 after heating the first gas G1 to the thermal decomposition temperature of NH ₃ by the preheating unit 73.

  Next, a method for manufacturing the silicon carbide substrate according to the present embodiment will be described. The method for manufacturing a silicon carbide substrate according to the present embodiment is carried out using CVD apparatus 1 which is a silicon carbide substrate manufacturing apparatus according to the present embodiment. Referring to FIG. 2, first, as a step (S10), a base substrate preparation step is performed. In this step (S10), referring to FIG. 3, for example, by slicing an ingot (not shown) made of 4H type hexagonal silicon carbide, it is made of silicon carbide, and has a front surface 10a and a back surface. A base substrate 10 having 10b is prepared.

  Next, a base substrate placement step is performed as a step (S20). In this step (S20), referring to FIG. 1, base substrate 10 prepared in step (S10) is placed on susceptor 6 of CVD apparatus 1.

  Next, as a step (S30), an epitaxially grown film forming step is performed. In this step (S30), the epitaxial growth film 11 is formed on the surface 10a of the base substrate 10 as described below (see FIG. 4).

Referring to FIG. 1, first, valves (not shown) provided in each of gas cylinders 71a to 71e are opened. As a result, the second gas G2 containing H ₂ , SiH ₄ , C ₃ H ₈ and HCl and not containing NH ₃ is supplied into the gas pipe 72b, and the first gas G1 containing NH ₃ is supplied into the gas pipe 72a. To be supplied.

Next, the first gas G1 is supplied to the preheating unit 73 through the gas pipe 72a. The first gas G1 by the preheating unit 73 is heated to the pyrolysis temperature of the NH ₃ (800 ° C. or higher 1000 ° C. or less). Thereby, at least a part of NH ₃ contained in the first gas G1, more preferably all NH ₃ is thermally decomposed. Next, the first gas G1 and the second gas G2 after pyrolysis are mixed in the gas pipe 72c to form a reaction gas G3.

Next, the reactive gas G3 is supplied into the quartz tube 8 through the gas pipe 72c. At this time, the reaction chamber 8a of the quartz tube 8 and the base substrate 10 disposed in the reaction chamber 8a are preheated to a predetermined temperature by the heating element 5 heated by the RF coil 9. . Then, when the reaction gas G3 is heated by the heating element 5, SiH ₄ and C ₃ H ₈ in the reaction gas G3 are thermally decomposed. As a result, an epitaxially grown film 11 made of silicon carbide doped with nitrogen (N) atoms is formed on the surface 10a of the base substrate 10 as shown in FIG. Thus, silicon carbide substrate 20 having base substrate 10 and epitaxial growth film 11 is manufactured by performing steps (S10) to (S30) described above, and manufacture of the silicon carbide substrate according to the present embodiment. The method is complete.

As described above, the method for manufacturing a silicon carbide substrate according to the present embodiment includes a step of preparing base substrate 10 made of silicon carbide (S10), a step of arranging prepared base substrate 10 (S20), Forming an epitaxial growth film 11 on the base substrate 10 (S30). Then, in step (S30), a first gas G1 containing NH _3, include HCl, based on the reaction gas G3 mixed with a second gas G2 containing no NH ₃ while supplying toward the base substrate 10 The substrate 10 is heated. The first gas G1 is heated to the thermal decomposition temperature of NH ₃ by the preheating unit 73 and then mixed with the second gas G2 in the gas pipe 72c.

Thus, in the method for manufacturing a silicon carbide substrate according to the present embodiment, reaction gas G3 containing NH ₃ that is easily pyrolyzed is used, and therefore silicon carbide substrate 20 with a more uniform nitrogen atom concentration is manufactured. can do. Moreover, in the method for manufacturing the silicon carbide substrate according to the present embodiment, since the reaction gas G3 containing HCl is used, the speed of epitaxial growth can be improved. Furthermore, in the method for manufacturing a silicon carbide substrate according to the present embodiment, the first gas G1 containing NH ₃ is heated to the thermal decomposition temperature of NH ₃ and then mixed with the second gas G2 containing HCl. A reaction gas G3 is formed. Therefore, it is possible to suppress the NH ₃ in the first gas G1 and the HCl in the second gas G2 from reacting before thermal decomposition and generating NH ₄ Cl, which is a solid byproduct. Thereby, it can suppress that the said by-product adheres to the growing epitaxial film, and the crystallinity of a silicon carbide substrate falls. Therefore, according to the method for manufacturing a silicon carbide substrate according to the present embodiment, silicon carbide substrate 20 having excellent impurity concentration uniformity and crystallinity can be efficiently manufactured.

Further, in the step (S30), the base substrate 10 may be heated in a state of being disposed inside the quartz tube 8. The first gas G1 may be mixed with the second gas G2 outside the quartz tube 8. More specifically, the first gas G1 is heated to the thermal decomposition temperature of NH ₃ by the preheating unit 73 disposed outside the quartz tube 8, and then, as shown in FIG. You may mix with 2nd gas G2 in a connection part with the piping 72c.

  Thereby, compared with the case where the first gas G1 and the second gas G2 are mixed in the quartz tube 8, the reaction gas G3 in which the first gas G1 and the second gas G2 are mixed more uniformly is used as the base substrate. 10 can be supplied. As a result, higher quality silicon carbide substrate 20 can be manufactured.

(Embodiment 2)
Next, the configuration of CVD apparatus 2 which is a silicon carbide substrate manufacturing apparatus according to Embodiment 2, which is another embodiment of the present invention, will be described. The CVD apparatus 2 according to the present embodiment basically has the same configuration as the CVD apparatus 1 according to the first embodiment and has the same effects. However, the CVD apparatus 2 according to the present embodiment is different from the CVD apparatus 1 according to the first embodiment in the configuration of the gas supply unit 7.

With reference to FIG. 5, in the CVD apparatus 2, the gas supply unit 7 mainly includes gas cylinders 71 a to 71 e, a first gas pipe 74, and a second gas pipe 75. The gas cylinders 71a to 71e are filled with H ₂ gas, SiH ₄ gas, C ₃ H ₈ gas, HCl gas and NH ₃ gas, respectively, as in the first embodiment. Each of the gas cylinders 71 a to 71 d is connected to the second gas pipe 75, and the gas cylinder 71 e is connected to the first gas pipe 74. Thus, the second gas pipe 75 comprises _{H 2, SiH 4, C 3} H 8 and HCl, supplying a second gas G2 containing no NH _3, and including a NH ₃ into the first gas pipe 74 It is possible to supply the first gas G1.

The first gas pipe 74 is a member for supplying the first gas G1 to the inside of the quartz tube 8, and is connected to the end of the quartz tube 8 at one end (right side in the drawing). The first gas pipe 74 has an insertion portion 74a that is a portion located inside the quartz tube 8 (a portion of the quartz tube 8 facing the heating element 5). That is, the first gas pipe 74 is in a state where one end (right side in the figure) is inserted into the quartz tube 8 as shown in FIG. Thus, the first gas G1 flowing through the insertion portion 74a can be heated to the thermal decomposition temperature of NH ₃ by the RF coil 9 and the heating element 5. The second gas pipe 75 is a member for supplying the second gas G <b> 2 to the inside of the quartz tube 8, and one end (right side in the drawing) is connected to the end of the quartz tube 8.

  Referring to FIGS. 5 and 6, the first gas pipe 74 is inserted into the quartz tube 8 so that the one end portion is not located above the susceptor 6. That is, the first gas pipe 74 is arranged so that the one end is located upstream of the susceptor 6 in the direction in which the reaction gas G3 flows. Accordingly, a predetermined interval can be maintained between the one end of the first gas pipe 74 including the supply port of the first gas G1 and the base substrate 10. As a result, the first gas G1 can be supplied to the base substrate 10 side in a more uniformly diffused state (arrow in FIG. 6).

  Referring to FIG. 7, the insertion portion 74 a has a gas flow path 74 b that constitutes the flow path of the first gas, and a gas supply port 74 c that has a shape that gradually expands toward the distal end. Also good. And the cross-sectional area of the insertion part 74a in the gas supply port 74c may be larger than the cross-sectional area of the insertion part 74a in the gas flow path 74b. This makes it easier to uniformly diffuse the first gas inside the quartz tube. In addition, the cross-sectional shape of the insertion part 74a in the gas supply port 74c is not limited to the rectangular shape as shown in FIG. 7, and other arbitrary shapes (for example, circular shape, square shape, other polygonal shapes, etc.) can do.

  Referring to FIG. 8, the insertion portion 74a may have a gas flow path 74b that forms the flow path of the first gas, and a gas supply port 74d that includes a plurality of branch portions 74e. Accordingly, as in the case described with reference to FIG. 7, it becomes easier to uniformly diffuse the first gas inside the quartz tube 8. The number of branching parts 74e may be three as shown in FIG. 8, but is not limited to this, and can be selected as appropriate. Moreover, the cross-sectional shape of the insertion part 74a in each branch part 74e is not limited to a circular shape as shown in FIG. 8, For example, it can be set as other arbitrary shapes, such as a rectangular shape. Further, the branch portions 74e may be formed along each other as shown in FIG. 8, but the direction of each of the branch portions 74e may be appropriately selected so as to diffuse the first gas more uniformly. Is possible.

  Next, a method for manufacturing the silicon carbide substrate according to the present embodiment will be described. Referring to FIG. 2, first, a base substrate preparation step (S10) and a base substrate arrangement step (S20) are performed as in the first embodiment. Thereby, base substrate 10 made of silicon carbide is arranged on susceptor 6 of CVD apparatus 2 (see FIG. 5).

  Next, as a step (S30), an epitaxially grown film forming step is performed. In this step (S30), the epitaxial growth film 11 is formed on the base substrate 10 as described in the first embodiment as described below (see FIG. 4).

Referring to FIG. 5, first, valves (not shown) provided in each of gas cylinders 71a to 71e are opened. As a result, the second gas G2 containing H ₂ , SiH ₄ , C ₃ H ₈ and HCl and not containing NH ₃ is supplied into the second gas pipe 75, and the first gas G1 containing NH ₃ is the first gas G1. It is supplied into the gas pipe 74.

Next, the first gas G1 supplied to the insertion portion 74a of the first gas pipe 74 is heated by the RF coil 9 and the heating element 5 to more than the thermal decomposition temperature of the NH _3. Thereby, at least a part of NH ₃ contained in the first gas G1 and more preferably all NH ₃ is thermally decomposed. Similarly, the second gas G2 supplied into the reaction chamber 8a through the second gas pipe 75 is heated by the RF coil 9 and the heating element 5. Thereby, SiH ₄ and C ₃ H ₈ in the second gas G2 are thermally decomposed. Next, the first gas G1 and the second gas G2 after pyrolysis are mixed in the reaction chamber 8a to form the reaction gas G3, and the reaction gas G3 is supplied toward the base substrate 10. Then, an epitaxial growth film 11 doped with nitrogen atoms is formed on the heated surface 10a of the base substrate 10 (see FIG. 4). Thus, by performing the above steps (S10) to (S30), silicon carbide substrate 20 having base substrate 10 and epitaxial growth film 11 is manufactured in the same manner as in the first embodiment. The manufacturing method of the silicon carbide substrate which concerns on a form is completed.

As described above, in the method for manufacturing the silicon carbide substrate according to the present embodiment, the second gas G2 is heated after the first gas G1 is heated to the thermal decomposition temperature of NH ₃ as in the first embodiment. Mixed. Therefore, the production of a byproduct (NH ₄ Cl) due to the reaction between NH ₃ contained in the first gas G1 and HCl contained in the second gas G2 is suppressed, and the crystallinity of the silicon carbide substrate due to this is reduced. Can be suppressed.

In addition, in the method for manufacturing a silicon carbide substrate according to the present embodiment, unlike the first embodiment, the base substrate 10 is heated in a state of being disposed inside the quartz tube 8 and the first gas G1 is quartz. After being heated inside the tube 8, it is mixed with the second gas G2. More specifically, the first gas G1 is heated to the thermal decomposition temperature of NH ₃ by the RF coil 9 and the heating element 5 for heating the base substrate 10, and then mixed with the second gas G2. Therefore, it is not necessary to separately provide a mechanism (preheating section 73) for heating the first gas G1 as in the first embodiment, and the apparatus configuration can be further simplified.

(Embodiment 3)
Next, the configuration of CVD apparatus 3 which is a silicon carbide substrate manufacturing apparatus according to Embodiment 3 which is still another embodiment of the present invention will be described. The CVD apparatus 3 according to the present embodiment basically has the same configuration as the CVD apparatuses 1 and 2 according to the first and second embodiments and has the same effects. However, the CVD apparatus 3 according to the present embodiment is different from the CVD apparatuses 1 and 2 according to the first and second embodiments in the configuration of the heating element 5 and the gas supply unit 7.

Referring to FIG. 9, in CVD apparatus 3, gas supply unit 7 basically has the same configuration as in the second embodiment. That is, the second gas G2 containing H ₂ , SiH ₄ , C ₃ H ₈ and HCl and not containing NH ₃ is supplied into the gas pipe 77, and the first gas G 1 containing NH ₃ is supplied into the gas pipe 76. It is possible to do. The gas pipes 76 and 77 are connected to the end of the quartz tube 8 at one end (right side in the figure). Here, in the present embodiment, the gas pipe 76 is connected to the quartz tube 8 without being inserted into the quartz tube 8 (the portion of the quartz tube 8 facing the heating element body 5c).

The heating element 5 includes a heating element main body 5c and an annular protrusion (guide) formed so as to protrude in the axial direction at one end of the heating element main body 5c (the end on the gas pipes 76 and 77 side). Part) 5d. A preheating region 5e is formed on the inner peripheral side of the guide portion 5d, and gas pipes 76 and 77 are arranged in the preheating region 5e. Therefore, by heating the preheating region 5e located on the inner peripheral side of the guide portion 5d using the RF coil 9, the gas pipes 76 and 77 located in the preheating region 5e can be heated. Thus, the first gas G1 supplied to the gas pipe 76 can be heated to the thermal decomposition temperature of NH _{3 in} the preheating region 5e. That is, unlike the case of the second embodiment, the first gas G1 may be preheated not in the portion of the quartz tube 8 facing the heating element body 5c but outside the portion (preheating region 5e). it can.

  Next, a method for manufacturing the silicon carbide substrate according to the present embodiment will be described. Referring to FIG. 2, first, a base substrate preparation step (S10) and a base substrate arrangement step (S20) are performed as in the first and second embodiments. Thereby, base substrate 10 made of silicon carbide is arranged on susceptor 6 of CVD apparatus 3 (see FIG. 9).

  Next, as a step (S30), an epitaxially grown film forming step is performed. In this step (S30), epitaxial growth film 11 is formed on base substrate 10 as described in the first and second embodiments as described below (see FIG. 4).

Referring to FIG. 9, first, valves (not shown) provided in each of gas cylinders 71a to 71e are opened. As a result, the second gas G2 containing H ₂ , SiH ₄ , C ₃ H ₈ and HCl and not containing NH ₃ is supplied into the gas pipe 77, and the first gas G 1 containing NH ₃ is contained in the gas pipe 76. To be supplied.

Next, the first gas G1 supplied into the gas pipe 76 is heated to a temperature equal to or higher than the thermal decomposition temperature of NH ₃ by the RF coil 9 and the guide portion 5d of the heating element 5 when passing through the preheating region 5e. . Thus, at least part of the NH ₃ contained in the pre-heating area 5e in the first gas G1, and more preferably NH ₃ in total are thermally decomposed. Similarly, the second gas G2 supplied into the gas pipe 77 is also heated in the preheating region 5e, so that at least a part of SiH ₄ , C ₃ H _{8 and the} like in the second gas G2 is thermally decomposed. The Next, the reaction gas G3 is formed by mixing the first gas G1 and the second gas G2 in the reaction chamber 8a, and the reaction gas G3 is supplied toward the base substrate 10. Then, an epitaxial growth film 11 doped with nitrogen atoms is formed on the heated surface 10a of the base substrate 10 (see FIG. 4). Thus, by performing the steps (S10) to (S30), silicon carbide substrate 20 having base substrate 10 and epitaxial growth film 11 is manufactured in the same manner as in the first and second embodiments. The method for manufacturing the silicon carbide substrate according to the embodiment is completed.

As described above, in the method for manufacturing the silicon carbide substrate according to the present embodiment, the second gas is heated after the first gas G1 is heated to the thermal decomposition temperature of NH ₃ as in the first and second embodiments. Mixed with G2. Therefore, the production of a byproduct (NH ₄ Cl) due to the reaction between NH ₃ contained in the first gas G1 and HCl contained in the second gas G2 is suppressed, and the crystallinity of the silicon carbide substrate due to this is reduced. Can be suppressed.

Further, in the method for manufacturing the silicon carbide substrate according to the present embodiment, the first gas G1 is heated to the thermal decomposition temperature of NH ₃ by the guide portion 5d formed on the heating element 5 in the preheating region 5e, and then quartz. Inside the tube 8, it is mixed with the second gas G2. For this reason, it is not necessary to separately provide the preheating unit 73 as in the first embodiment, and the first gas G1 is not inserted into the quartz tube 8 as in the second embodiment. Preheating heating can be performed before mixing with the two gases G2. Thereby, it is possible to prevent the gas pipe from being melted by the heat in the quartz pipe 8 by inserting the gas pipe into the quartz pipe 8.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The method and apparatus for manufacturing a silicon carbide substrate according to the present invention are particularly applicable to a method and apparatus for manufacturing a silicon carbide substrate that is required to efficiently manufacture a silicon carbide substrate having excellent impurity concentration uniformity and crystallinity. It can be advantageously applied.

  1, 2, 3 CVD apparatus, 4 heat insulating material, 4a, 5a, 8b inner peripheral surface, 5 heating element, 5b recess, 5c heating element body, 5d protrusion (guide part), 5e preheating region, 6 susceptor, 7 Gas supply unit, 8 quartz tube, 8a reaction chamber, 8c outer peripheral surface, 9 RF coil, 10 base substrate, 10a surface, 10b back surface, 11 epitaxial growth film, 20 silicon carbide substrate, 71a, 71b, 71c, 71d, 71e gas cylinder, 72a, 72b, 72c, 76, 77 Gas piping, 73 Preheating section, 74 First gas piping, 74a Insertion section, 74b Gas flow path, 74c, 74d Gas supply port, 74e Branching section, 75 Second gas piping, G1 First gas, G2 second gas, G3 reaction gas.

Claims (8)

Preparing a base substrate made of silicon carbide;
Forming an epitaxial growth film on the base substrate,
In the step of forming the epitaxial growth film,
The base substrate is heated in a state where a reaction gas obtained by mixing a first gas containing ammonia and a second gas containing hydrogen chloride and not containing ammonia is supplied toward the base substrate,
The method for manufacturing a silicon carbide substrate, wherein the first gas is heated to a thermal decomposition temperature of ammonia and then mixed with the second gas. In the step of forming the epitaxial growth film,
The base substrate is heated in a state of being disposed inside the reaction tube,
The method for manufacturing a silicon carbide substrate according to claim 1, wherein the first gas is mixed with the second gas outside the reaction tube.   The method for manufacturing a silicon carbide substrate according to claim 2, wherein the first gas is heated to the pyrolysis temperature by a preheating unit disposed outside the reaction tube. In the step of forming the epitaxial growth film,
The base substrate is heated in a state of being disposed inside the reaction tube,
The method for manufacturing a silicon carbide substrate according to claim 1, wherein the first gas is mixed with the second gas inside the reaction tube.   The method for manufacturing a silicon carbide substrate according to claim 4, wherein the first gas is heated to the pyrolysis temperature by a heating unit for heating the base substrate. A reaction tube for disposing a base substrate made of silicon carbide inside;
A heating unit for heating the base substrate;
A gas supply unit for supplying a reaction gas for forming an epitaxially grown film on the base substrate into the reaction tube;
The gas supply unit
Configured to be able to supply the reaction gas obtained by mixing the first gas containing ammonia and the second gas containing hydrogen chloride and not containing ammonia into the reaction tube; and
An apparatus for manufacturing a silicon carbide substrate, wherein the first gas is heated to a thermal decomposition temperature of ammonia and then mixed with the second gas.   The said carbide | carbonized_material supply part is an exterior of the said reaction tube, The manufacturing apparatus of the silicon carbide substrate of Claim 6 containing the preheating part for heating the said 1st gas to the said thermal decomposition temperature. The gas supply unit
A first gas pipe having a portion located inside the reaction tube and supplying the first gas into the reaction tube;
The apparatus for manufacturing a silicon carbide substrate according to claim 6, further comprising a second gas pipe for supplying the second gas into the reaction tube.

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