JP2006028625A - Cvd apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CVD apparatus for uniformly and stably forming an epitaxial film on a semiconductor substrate, even when employing a susceptor made from a carbon material. <P>SOLUTION: This CVD apparatus has susceptors (11 and 12) made from the carbon material and the semiconductor substrate 70 made from silicon carbide (SiC) as well, arranged in a vessel 10; and forms the epitaxial film on the surface of the semiconductor substrate 70, while heating the semiconductor substrate 70 through heating a lower part of the susceptor 12, and supplying a carrier gas containing hydrogen gas (H<SB>2</SB>) and a source gas consisting of silane gas (SiH<SB>4</SB>) and propane gas(C<SB>3</SB>H<SB>8</SB>), into the vessel 10. At least the surface facing the semiconductor substrate 70 of the lower susceptor 12 is previously coated with a film material 16 having high etching resistance to the carrier gas, such as a pyrolytic carbon film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a CVD (chemical vapor deposition) apparatus for forming (growing) an epitaxial film on a semiconductor substrate.

  Conventionally, as an apparatus for forming an epitaxial film on a semiconductor substrate, for example, an apparatus described in Patent Document 1 is known. FIG. 4 shows an outline of the apparatus described in Patent Document 1.

As shown in FIG. 4, this apparatus mainly includes a film forming chamber 100, a gas inflow pipe 108, a plate 101 that supports a semiconductor substrate (wafer) 70, a heating unit 72, and a gas exhaust pipe 109. The Here, a tip nozzle 108 a of the gas inflow pipe 108 is disposed in the center of the inside of the film forming chamber 100, and the plate 101 is attached at a substantially right angle near the tip of the gas inflow pipe 108. Further, the semiconductor substrate 70 is disposed on the upper surface of the plate 101, and the semiconductor substrate 70 is heated by a heating unit 72 provided on the lower surface of the plate 101. The gas inflow pipe 108 is a supply source of hydrogen gas (H ₂ ), dichlorosilane gas (SiH ₂ Cl ₂ ), nitrogen gas (N ₂ ), and acetylene gas (C ₂ H ₂ ) outside the film forming chamber 100. Are connected to each other via valves v1 to v4. On the other hand, the film forming chamber 100 is provided with a gas exhaust pipe 109 connected to an exhaust pump (not shown) so that the gas in the film forming chamber 100 can be exhausted through the pressure adjusting valve v5.

  In the apparatus configured as described above, the semiconductor substrate 70 disposed on the plate 101 is first heated to an appropriate temperature such as “1200 ° C.” by the heating unit 72. Next, while the gas exhaust pipe 109 exhausts the film forming chamber 100, the gas is sequentially supplied from the gas introduction pipe 108 into the film forming chamber 100, and a gas phase corresponding to the gas is supplied into the film forming chamber 100. Form. As a result, the epitaxial film 80 is formed on the surface of the semiconductor substrate 70.

In recent years, as the semiconductor substrate, silicon carbide (SiC) has been attracting attention as a material capable of realizing an element having high thermal conductivity, high heat resistance, high dielectric breakdown electric field, and high power characteristics. Expected as a material. Further, in the case of using such a semiconductor substrate made of silicon carbide (SiC), an epitaxial film made of silicon carbide (SiC) having a higher purity is often formed through the above apparatus (CVD apparatus), whereby the semiconductor substrate is formed. As a result, further improvement of functions is attempted.
JP 2002-57109 A

  By the way, as a susceptor that is a so-called substrate (wafer) holder such as the plate 101 provided in the CVD apparatus, in recent years, it has high electrical conductivity, high heat resistance, and high purity so that the semiconductor wafer is not contaminated. The carbon material which is the material of is used. When such a carbon material is used, the surface is further made of a silicon carbide (SiC) film for the purpose of suppressing the dropping of carbon powder from the surface and suppressing the surface diffusion of a small amount of impurity elements due to heating. I often coat.

However, when such a carbon material is used for the susceptor 101, the silicon carbide (SiC) substrate is used as a semiconductor substrate, and the susceptor is heated to about “1500 ° C.” in order to form the epitaxial film thereon. The inventors have confirmed that the surface of the susceptor reacts with hydrogen gas (H ₂ ) as a carrier gas. When the susceptor surface reacts with hydrogen gas (H ₂ ) in this way, the carbon material or silicon carbide (SiC) film on the susceptor surface is etched to generate carbon particles, which are epitaxial films being formed. Defects are generated in the epitaxial film by adhering to the surface of the film. Further, when the carbon material or the silicon carbide (SiC) film reacts with the hydrogen gas (H ₂ ), the hydrocarbon gas is generated at the same time, so that the carbon / silicon ratio in the gas phase (C / Si) ) Becomes unstable. This is also one of the factors that cause defects in the epitaxial film. Furthermore, even if the surface of the susceptor made of a carbon material is coated with the silicon carbide (SiC) film, if the etching proceeds as described above, the silicon carbide (SiC) film itself disappears in a short time. It will also end up.

  The present invention has been made in view of such circumstances, and provides a CVD apparatus capable of forming an epitaxial film uniformly and stably on a semiconductor substrate even when a carbon material is used as a susceptor. For the purpose.

  In order to achieve such an object, in the CVD apparatus according to claim 1, a susceptor made of a carbon material is provided in a container, and the substrate placed in the container is heated based on the susceptor being heated, As a CVD apparatus for supplying a carrier gas and a source gas into the container to form an epitaxial film on the surface of the substrate, a film material having a high etching resistance to the carrier gas on at least the surface of the susceptor facing the substrate It was decided to form a film.

As described above, the carbon material is an excellent material as a susceptor of the CVD apparatus because it has high electrical conductivity and high heat resistance, but it is a carrier gas, particularly hydrogen gas (H ₂ used for normal epitaxial growth). It is easy to react chemically with the carrier gas containing), and the etching resistance to the carrier gas is low. In this regard, as in the CVD apparatus according to claim 1, the carbon material is etched by forming a film material having high etching resistance against the carrier gas on at least the surface of the susceptor facing the substrate. As a result, the generation of particles of the carbon material due to the formation of the carbon material is suppressed, and as a result, the epitaxial film can be uniformly formed on the substrate, particularly the semiconductor substrate (wafer). In particular, in the method of heating the substrate by heating the susceptor facing the substrate, the temperature of the susceptor that heats the substrate is higher than that of the substrate, so that the surface of the susceptor is the most easily etched by the carrier gas. . For this reason, it is important to form a film material having high etching resistance against the carrier gas on at least the surface of the susceptor facing the substrate. Moreover, even when a carrier gas containing the hydrogen gas (H ₂ ) is used as a carrier gas by forming a film material having high etching resistance against the carrier gas on the susceptor made of the carbon material, Generation of hydrocarbon gas due to the reaction between the carbon material and hydrogen is also suppressed. That is, since the carbon / silicon ratio (C / Si) in the gas phase is stabilized and the carrier concentration in the epitaxial film is kept uniform, the epitaxial film can be formed more stably. You will be able to

  Further, according to the second aspect of the present invention, if a material containing carbon is employed as the film material having high etching resistance to the carrier gas, the penetration and surface of the carbon material forming the susceptor Coating is also easy. Moreover, high electrical conductivity and heat resistance can be maintained as the susceptor itself.

  Further, according to the invention described in claim 3, if such a film material has a denser structure than the carbon material forming the susceptor, the etching resistance against the carrier gas is adopted. As a result, the mechanical strength and impact resistance of the film material itself can be improved, and as a result, the durability of the susceptor can be improved.

  As such a film material, specifically, a material such as a “pyrolytic carbon film” according to the invention described in claim 4 or a “metal carbide film” according to the invention described in claim 5 is employed. It is effective.

  These “pyrolytic carbon film” and “metal carbide film” have higher density and higher purity than the carbon material forming the susceptor. For this reason, impurities contained in these film materials are reduced as compared with the carbon material, and a higher purity epitaxial film can be formed.

In particular, as the “metal carbide film”, as in the invention described in claim 6, tantalum carbide (TaC), dimolybdenum carbide (Mo ₂ C), titanium carbide (TiC), zirconium carbide (ZrC), This can be realized as a film material containing at least one of vanadium carbide (VC), tungsten carbide (WC), and niobium carbide (NbC). Since these materials have better heat resistance than the carbon material forming the susceptor, the etching resistance to the carrier gas can be maintained high even when the susceptor is heated to a high temperature. become.

And in the CVD apparatus according to any one of claims 1 to 6, particularly when the substrate is a silicon carbide (SiC) substrate as in the invention according to claim 7, A gas containing hydrogen gas (H ₂ ) as the carrier gas and silane gas (SiH ₄ ) and propane gas (C ₃ H ₈ ) as the source gas are supplied into the container, respectively, and carbonized on the surface of the substrate. By configuring this as an apparatus for growing an epitaxial film made of silicon (SiC), the growth of the epitaxial film made of silicon carbide (SiC) on the silicon carbide (SiC) substrate described above can be made more uniform and stable. Will be able to do.

Further, in this case, as in the invention according to claim 8, it is particularly desirable that the concentration of nitrogen contained in the film material is “1 ppm” or less. In general, in order to employ a silicon carbide (SiC) film as an epitaxial film as various device materials, the carrier concentration in the film is often controlled to be “1 × 10 ¹⁶ cm ⁻³ ” or less. Therefore, by setting the background impurity concentration to be “one digit” lower than that, it is possible to realize the formation of such a high-quality epitaxial film. Further, since nitrogen becomes an n-type impurity for silicon carbide (SiC), the influence of the nitrogen being taken into the epitaxial film can be reduced as much as possible by setting the concentration of nitrogen contained in the film material to “1 ppm” or less. You can also. As a result, an epitaxial film maintained at a low background impurity concentration is grown.

  In the CVD apparatus according to any one of claims 1 to 8, the susceptor is heated by high-frequency induction heating as in the invention according to claim 9, so that the susceptor, and thus the substrate is heated. Can be more easily and uniformly performed. In addition, the degree of freedom in designing the CVD apparatus itself can be increased. That is, in this case, for example, by providing a coil for supplying high-frequency current to the outside of the container, such heating and control thereof can be performed. Therefore, the layout of the inside of the container can be designed relatively freely. Will be able to.

On the other hand, as a configuration of the CVD apparatus itself based on the invention according to any one of claims 1 to 9, for example, according to the invention according to claim 10,
(A1) The susceptor has a two-stage structure including an upper susceptor disposed above the gravity direction and a lower susceptor disposed below the gravity direction.
(A2) About the said board | substrate, this is installed in the board | substrate holder provided in the said upper susceptor, and the surface is made to oppose the said lower susceptor.
(A3) The carrier gas and the source gas are circulated between the opposing substrate and the lower susceptor.
(A4) A film material having high etching resistance to the carrier gas is formed on at least the surface of the lower susceptor facing the substrate.
Such a configuration is effective. According to such a configuration as a CVD apparatus, in addition to the effects of the above-described inventions, the source gas is supplied substantially in the vicinity of the surface of the substrate so that the epitaxial film is sequentially formed on the surface. Therefore, the film forming rate is naturally improved, and the necessary source gas can be reduced to the minimum necessary amount. In particular, since the surface of the substrate on which the epitaxial film is formed faces the direction of gravity, even if particles or the like are generated due to the etching of the film material, the surface of the epitaxial film Adhesion to the surface is suppressed. Further, in the CVD apparatus having such a configuration, by arranging a plurality of substrates in the container, an epitaxial film can be simultaneously formed on the surfaces of these substrates, and the efficiency of such film formation can be increased.

  Further, in the CVD apparatus having such a configuration, as in the invention described in claim 11, a rotating mechanism that rotates the substrate together in the circumferential direction in a state where the substrate is arranged on the substrate holder. If provided, the film formation rate (film thickness) of the epitaxial film to be formed can be maintained more uniformly.

On the other hand, as a structure of the CVD apparatus itself based on the invention according to any one of claims 1 to 9, for example, according to the invention according to claim 12,
(B1) The substrate is held in the vertical direction by an appropriate substrate holder.
(B2) The susceptor is formed in a cylindrical shape so as to cover the surface of the substrate held in the vertical direction.
(B3) The carrier gas and the source gas are circulated in the vertical direction between the substrate and the susceptor.
(B4) The film material having high etching resistance to the carrier gas is formed on at least the surface of the cylindrical susceptor facing the substrate.
Such a configuration is also effective. Even with such a configuration as a CVD apparatus, in addition to the effects of the above-described inventions, the source gas is directly supplied near the surface of the substrate, and an epitaxial film is sequentially formed on the surface. Therefore, the film forming rate is naturally improved, and the necessary source gas can be reduced to the minimum necessary amount. Also in this case, the substrate is disposed such that the surface on which the epitaxial film is formed is substantially parallel to the vertical direction, so that the particles are caused even if the film material is etched. Even if such occurs, adhesion to the surface of the epitaxial film is suppressed. Furthermore, in the CVD apparatus having such a configuration, since at least two substrates can be disposed on the cylindrical susceptor, an epitaxial film can be simultaneously formed on the surfaces of these substrates. Efficiency can also be increased.

(First embodiment)
A first embodiment of a CVD apparatus according to the present invention will be described below with reference to FIG. In the CVD apparatus according to this embodiment, for example, a CVD apparatus for forming an epitaxial film made of silicon carbide (SiC) with higher purity on the surface of a semiconductor substrate (wafer) made of a single crystal of silicon carbide (SiC). It is configured as.

  As shown in FIG. 1, heat insulating materials 71 a and 71 b are provided on the upper surface side and the bottom surface side inside the container 10 of this CVD apparatus, respectively. Of these, the heat insulating material 71a provided on the upper surface side of the container 10 is provided with the upper susceptor 11 made of a carbon material so as to be adjacent thereto, while being provided on the bottom surface side of the container 10. A lower susceptor 12 made of a carbon material is disposed on the heat insulating material 71b so as to be adjacent thereto. The upper susceptor 11 and the lower susceptor 12 are disposed so as to face each other with a predetermined interval, for example, a gap of about “10 to 40 mm”. Between them is a distribution path for the source gas.

  Here, the upper susceptor 11 is provided with a recess 11a on the surface facing the lower susceptor 12, and a through hole 13 is formed at the center of the recess 11a. A disc-shaped substrate holder 14 supported by a rotating shaft 15 inserted through the through hole 13 is disposed in the recess 11a. A semiconductor substrate 70 made of a single crystal of silicon carbide (SiC) is mounted on the substrate holder 14 by an appropriate pressing mechanism, for example, and the surface thereof faces the lower susceptor 12 downward. When the rotating shaft 15 is rotated by a power source such as a motor (not shown), the substrate 70 is rotated together with the substrate holder 14 based on this rotation.

On the other hand, a film material 16 made of a pyrolytic carbon film is formed on the surface of the lower susceptor 12. This pyrolytic carbon film is a well-known carbon film produced by pyrolyzing a hydrocarbon gas such as propane gas (C ₃ H ₈ ) or a hydrocarbon compound, and the upper susceptor 11 and the lower susceptor 12. It has a denser structure and higher purity than the carbon material that forms the material. The film material 16 made of the pyrolytic carbon film is formed by a CVD method (chemical vapor deposition method) or the like so that the film thickness becomes about “20 to 60 μm”. Further, the concentration of nitrogen contained in the film material 16 is controlled to be “1 ppm” or less.

And the coil 72 is provided in the outer wall surface of the bottom face side of the container 10, The said lower susceptor 12 is induction-heated by electricity supply of the high frequency current to this coil 72. As shown in FIG.
Further, a supply port and a discharge port for the source gas and the carrier gas are formed on the end face in the longitudinal direction of the container 10. In the CVD apparatus according to this embodiment, a gas mainly composed of propane gas (C ₃ H ₈ ) and silane gas (SiH ₄ ) is used as the source gas, and hydrogen gas (H ₂ ) is used as the carrier gas. Each of these gases is used. Then, the processing gas G in which these are mixed flows between the upper susceptor 11 and the lower susceptor 12 in the manner indicated by the arrow in FIG. It is discharged outside.

Next, a procedure for forming a silicon carbide (SiC) film on the substrate 70 using the CVD apparatus having such a structure will be described.
When forming the film, first, the semiconductor substrate 70 to be deposited is mounted on the substrate holder 14, the container 10 is closed, and the substrate holder 14 is rotated together with the substrate 70, and the carrier is placed in the container 10. While introducing the gas, a high-frequency current set to a frequency of, for example, about “8 kHz” is passed through the coil 72. Thereby, the lower susceptor 12 on the bottom surface side is first induction-heated, and then the surface of the upper susceptor 11, the substrate holder 14, and the substrate 70 is set to, for example, “1500 ° C.” or more by the radiant heat of the lower susceptor 12. Heated. In this way, with the surface of the substrate 70 sufficiently heated, the source gas is introduced into the container 10 in addition to the carrier gas. Thereby, the source gas is thermally decomposed on the surface of the substrate 70, and an epitaxial film made of a single crystal of silicon carbide (SiC) is formed on the surface of the substrate 70. At this time, the carrier concentration in the epitaxial film is “1 × 10 ¹⁶ cm ⁻³ ” by setting the nitrogen concentration in the film material 16 facing the substrate 70 to “1 ppm” or less as described above. The following can be controlled. At this time, since the substrate 70 is rotating, the portion located on the upstream side of the source gas in the surface of the substrate 70 is sequentially replaced, and the epitaxial film is formed while maintaining a uniform film thickness distribution. It also comes to be. In addition, in this embodiment, as described above, the film material 16 made of the pyrolytic carbon film is formed in advance on the surface of the lower susceptor 12. As a result, the generation of particles of the carbon material resulting from the reaction of the carbon material forming the susceptor 12 with the hydrogen (H ₂ ) contained in the carrier gas and etching is suppressed. The epitaxial film is formed uniformly on the top. In addition, by forming the film material 16 having high etching resistance against the carrier gas on the lower susceptor 12, generation of hydrocarbon gas due to the reaction between the carbon material and hydrogen is also suppressed. That is, since the carbon / silicon ratio (C / Si) in the gas phase is stabilized and the carrier concentration in the epitaxial film is kept uniform, the epitaxial film can be formed more stably. You will be able to

As described above, according to the CVD apparatus according to this embodiment, the effects listed below can be obtained.
(1) Of the susceptors 11 and 12 made of a carbon material, the surface of the lower susceptor 12 provided on the bottom surface side of the container 10 and induction-heated is made of a pyrolytic carbon film having high etching resistance against hydrogen gas (H ₂ ). The film material 16 is formed in advance. By adopting such a structure, the generation of carbon material particles is suppressed, and the carbon / silicon (C / Si) in the gas phase is stabilized and the carrier concentration in the epitaxial film is kept uniform. Therefore, the epitaxial film can be formed uniformly and stably. Further, such a pyrolytic carbon film has higher density and higher purity than the carbon material forming the susceptor 12. For this reason, impurities contained in the carbon material are apparently reduced by the coating in the pyrolytic carbon film, and a higher purity epitaxial film can be formed.

  (2) As the film material 16, a material containing carbon is adopted. With such a structure, the carbon material forming the susceptor 12 can be easily penetrated and the surface can be covered, and the susceptor 12 itself can maintain high electrical conductivity and heat resistance.

  (3) Similarly, the film material 16 has a structure with a higher density than the carbon material forming the susceptor 12. With such a structure, the etching resistance against the carrier gas can be improved, and the mechanical strength and impact resistance of the film material 16 itself can be improved. As a result, the durability of the susceptor 12 can be improved. Comes to be planned.

(4) A silicon carbide (SiC) substrate is used as the semiconductor substrate 70 to be formed, a gas containing hydrogen gas (H ₂ ) as a carrier gas, and silane gas (SiH ₄ ) and propane gas ( C ₃ H ₈ ) is supplied into the container 10 to grow an epitaxial film made of silicon carbide (SiC) on the substrate 70. With such a structure, the growth of the epitaxial film made of silicon carbide (SiC) on the substrate 70 made of silicon carbide (SiC) can be more uniformly and stably performed.

(5) The nitrogen concentration contained in the film material 16 is set to be “1 ppm” or less. If the impurity concentration in the background of the epitaxial film can be controlled in this way, the carrier concentration in the epitaxial film can be set as required for silicon carbide (SiC) films generally used as various devices. It becomes possible to control to “1 × 10 ¹⁶ cm ⁻³ ” or less. That is, this makes it possible to form an epitaxial film having higher quality.

  (6) The lower susceptor 12 is heated by a coil 72 to which a high frequency current is supplied. According to such a configuration, the lower susceptor 12 and thus the substrate 70 can be heated more easily and uniformly. In addition, the degree of freedom in designing the CVD apparatus itself can be increased. That is, for example, by providing the coil 72 outside the container 10, such heating and control thereof can be performed, so that the layout and the like of the inside of the container 10 can be designed relatively freely.

  (7) By adopting the above-described configuration as the configuration of the CVD apparatus itself, the source gas is supplied substantially in the vicinity of the surface of the substrate 70, and an epitaxial film is sequentially formed on the surface. Therefore, the film forming rate is naturally improved, and the necessary source gas can be reduced to the minimum necessary amount. In particular, since the surface of the substrate 70 on which the epitaxial film is formed faces downward in the direction of gravity, even if particles or the like are generated due to the etching of the film material 16, the epitaxial film Adhesion to the surface is suppressed.

  (8) The substrate holder 14 is provided with a rotation mechanism that rotates the substrate 70 in the circumferential direction in a state where the substrate 70 is disposed. With such a configuration, the film formation rate (film thickness) of the epitaxial film to be formed can be maintained more uniformly.

(Second Embodiment)
Next, a second embodiment of the CVD apparatus according to the present invention will be described with reference to FIG. The CVD apparatus according to this embodiment is also an apparatus for forming an epitaxial film made of silicon carbide (SiC) with higher purity on the surface of a semiconductor substrate (wafer) made of a single crystal of silicon carbide (SiC), for example. The basic structure of the CVD apparatus is the same as that of the first embodiment. However, in this case, an epitaxial film can be simultaneously formed on a plurality of semiconductor substrates in the container.

  In the CVD apparatus according to this embodiment, the container 20 has a cylindrical shape, for example. As shown in FIG. 2, a supply port for the source gas and the carrier gas is formed at the center of the bottom surface of the cylindrical container 20, and a discharge port for these gases is formed at a plurality of locations on the side surface. . In addition, substantially disc-shaped heat insulating materials 71c and 71d are provided on the upper surface side and the middle of the inside of the container 20, respectively.

  A disc-shaped upper susceptor 21 made of a carbon material is disposed adjacent to the heat insulating material 71c provided on the upper surface side of the container 20, and the entire upper susceptor 21 is disposed at the center thereof. A rotating shaft 25c for rotating the is attached. A plurality of recesses 21a and 21b are provided around the rotary shaft 25c of the upper susceptor 21, and through holes 23a and 23b are formed in the centers of the recesses 21a and 21b, respectively. Disc-shaped substrate holders 24a and 24b supported by rotating shafts 25a and 25b inserted through the through holes 23a and 23b are respectively disposed in the recesses 21a and 21b. Similar to the first embodiment, semiconductor substrates 70a and 70b are mounted on the substrate holders 24a and 24b, and the surfaces of the substrate holders 24a and 24b face the lower susceptor 22 described below. . The rotation shafts 25a and 25b and the rotation shaft 25c are substantially parallel, and the substrate holders 24a and 24b and the substrates 70a and 70b rotate around the rotation shafts 25a and 25b, and at the same time the upper portion around the rotation shaft 25c. The susceptor 21 also rotates.

On the other hand, the middle heat insulating material 71d facing the upper susceptor 21 has a disk-shaped lower susceptor made of a carbon material so as to be adjacent to the upper susceptor 21. A cylindrical susceptor 22a is also arranged along the wall surface of the gas supply port below it. Of these, a film material 26 made of a pyrolytic carbon film is formed on the surface of the lower susceptor 22. This pyrolytic carbon film is also a well-known carbon film produced by pyrolyzing a hydrocarbon-based gas such as propane gas (C ₃ H ₈ ) or a hydrocarbon compound. The upper susceptor 21 and the lower susceptor 22 are also known. It has a denser structure and higher purity than the carbon material that forms the material. The film material 26 made of the pyrolytic carbon film is also formed by the CVD method (chemical vapor deposition method) or the like so that the film thickness becomes about “20 to 60 μm”. Further, the concentration of nitrogen contained in the film material 26 is controlled to be “1 ppm” or less.

In addition, a coil 72 is provided below the heat insulating material 71 d in the middle of the container 20, and the lower susceptor 22 is induction-heated by energizing the coil 72 with a high-frequency current.
In the CVD apparatus according to this embodiment, a gas mainly composed of propane gas (C ₃ H ₈ ) and silane gas (SiH ₄ ) is used as the source gas, and hydrogen gas (H ₂ ) is used as the carrier gas. Each of these gases is used. However, in this CVD apparatus, the processing gas G consisting of the carrier gas and the raw material gas is circulated in the vertical direction from the bottom surface side of the container 20 to the middle of the container 20 in the manner indicated by the arrow in FIG. After flowing in the outer peripheral direction of the container 20 along the susceptor 21 and flowing substantially parallel to the surfaces of the substrates 70a and 70b, the container 20 is discharged to the outside.

Next, a procedure for forming a silicon carbide (SiC) film on the substrates 70a and 70b using the CVD apparatus having such a structure will be described.
When forming the film, first, the semiconductor substrates 70a and 70b to be formed are mounted on the substrate holders 24a and 24b, respectively, the container 20 is closed, and both the substrates 70a and 70b and the substrate holders 24a and 24b The upper susceptor 21 is rotated. In addition, a carrier gas is introduced into the container 20 and a high-frequency current set to a frequency of, for example, about 8 kHz is passed through the coil 72. As a result, the lower susceptor 22 is first induction-heated, and then the surface of the upper susceptor 21, the substrate holders 24 a and 24 b, and the substrates 70 a and 70 b is increased to, for example, “1500 ° C.” or more by the radiant heat of the lower susceptor 22. It is heated to become. In this way, the raw material gas is introduced into the container 20 in addition to the carrier gas in a state where the surfaces of the substrates 70a and 70b are sufficiently heated. Thereby, the source gas is thermally decomposed on the surfaces of the substrates 70a and 70b, and an epitaxial film made of a single crystal of silicon carbide (SiC) is simultaneously formed on the surfaces of the substrates 70a and 70b. At this time, the carrier concentration in the epitaxial film is set to “1 × 10 ¹⁶ cm” by controlling the nitrogen concentration in the film material 26 facing the substrates 70a and 70b to “1 ppm” or less as described above. ^-3 "can be controlled below. Also at this time, since the substrates 70a and 70b are rotating, portions of the surfaces of the substrates 70a and 70b located on the upstream side of the source gas are sequentially replaced, and the epitaxial film has a uniform thickness distribution. The film can be formed while keeping it. In addition, also in the CVD apparatus according to this embodiment, the film material 26 made of the pyrolytic carbon film is formed in advance on the surface of the lower susceptor 22 as in the first embodiment. As a result, the generation of particles of the carbon material resulting from the reaction of the carbon material forming the susceptor 22 with the hydrogen (H ₂ ) contained in the carrier gas and etching is suppressed. The epitaxial film is formed uniformly on the top. Further, by forming the film material 26 having a high etching resistance against the carrier gas on the lower susceptor 22, the generation of hydrocarbon gas due to the reaction between the carbon material and hydrogen is also suppressed. That is, since the carbon / silicon ratio (C / Si) in the gas phase is stabilized and the carrier concentration in the epitaxial film is kept uniform, the epitaxial film can be formed more stably. You will be able to

  As described above, the CVD apparatus according to the second embodiment can obtain the same or similar effects as the effects (1) to (8) of the first embodiment. In addition, the following effects can be obtained.

  (9) The upper susceptor 21 is provided with a plurality of substrate holders 24a and 24b, and a plurality of substrates 70a and 70b are attached to the substrate holders 24a and 24b, respectively. With such a configuration, an epitaxial film can be simultaneously formed on the surfaces of the plurality of substrates 70a and 70b, and the production efficiency can be greatly increased.

(Third embodiment)
Next, a third embodiment of the CVD apparatus according to this embodiment will be described with reference to FIG. The CVD apparatus according to this embodiment is also an apparatus for forming an epitaxial film having a higher purity on the surface of a semiconductor substrate (wafer). The internal configuration including the container is the first and second structures described above. This is different from the embodiment.

  Also in this CVD apparatus, the container 30 has a cylindrical shape (not limited to a cylindrical shape). As shown in FIG. 3, a substrate holder 31 is disposed at the center of the container 30. On the surface of the substrate holder 31, two semiconductor substrates 70a and 70b are held in such a manner that the surfaces are substantially parallel to the vertical direction.

  On the other hand, a heat insulating material 71e is disposed on the inner wall surface of the container 30 in a cylindrical shape. A cylindrical susceptor 32 made of a carbon material is provided on the heat insulating material 71e so as to be adjacent to the heat insulating material 71e so as to cover the semiconductor substrates 70a and 70b. And between these board | substrates 70a and 70b and the susceptor 32 becomes a distribution channel of process gas.

Also in this embodiment, a film material 36 made of a pyrolytic carbon film is formed on the surface of the susceptor 32. The pyrolytic carbon film is also well known of the carbon film produced by pyrolysis of propane gas (C ₃ H ₈₎ hydrocarbon gas or hydrocarbon compounds such as such as a carbon material for forming the susceptor 32 It has a denser structure and higher purity. The film material 36 made of the pyrolytic carbon film is formed by a CVD method (chemical vapor deposition method) or the like so that the film thickness becomes about “20 to 60 μm”. Further, the concentration of nitrogen contained in the film material 36 is controlled to be “1 ppm” or less.

A coil 72 is provided on the outer wall surface of the container 30, and the susceptor 32 is induction-heated by energizing the coil 72 with a high-frequency current.
In the CVD apparatus according to this embodiment, a gas mainly composed of propane gas (C ₃ H ₈ ) and silane gas (SiH ₄ ) is used as the source gas, and hydrogen gas (H ₂ ) is used as the carrier gas. Each of these gases is used. And in this embodiment, these mixed process gas G distribute | circulates from the perpendicular direction downward to the upper direction in the aspect pointed at in FIG. At this time, the substrate holder 31 is formed in a wedge shape so as to face downward in the vertical direction, so that such a decrease in the flow rate of the processing gas can be suppressed.

Next, a procedure for forming a silicon carbide (SiC) film on the substrates 70a and 70b using the CVD apparatus having such a structure will be described.
When forming the film, first, the semiconductor substrates 70a and 70b to be formed are respectively disposed on the substrate holder 31, and then the container 30 is closed and the carrier gas is introduced into the container 30, For example, a high-frequency current set to a frequency of about 8 kHz is supplied to 72. As a result, the susceptor 32 is first induction-heated, and then the surface of the substrate holder 31 and the substrates 70a and 70b is heated to, for example, “1500 ° C.” or more by the radiant heat of the susceptor 32. In this way, the raw material gas is introduced into the container 30 in addition to the carrier gas with the surfaces of the substrates 70a and 70b sufficiently heated. Thereby, the source gas is thermally decomposed on the surfaces of the substrates 70a and 70b, and an epitaxial film made of a single crystal of silicon carbide (SiC) is simultaneously formed on the surfaces of the substrates 70a and 70b. At this time, the carrier concentration in the epitaxial film is set to “1 × 10 ¹⁶ cm” by controlling the nitrogen concentration in the film material 36 facing the substrates 70a and 70b to “1 ppm” or less as described above. ^-3 "can be controlled below. Moreover, also in the CVD apparatus according to this embodiment, the film material 36 made of the pyrolytic carbon film is formed in advance on the surface of the susceptor 32 as in the first and second embodiments. Yes. Thereby, the generation of particles of the carbon material resulting from the reaction of the carbon material forming the susceptor 32 with the hydrogen (H ₂ ) contained in the carrier gas to be etched is suppressed, and as a result, the substrate 70a. , 70b is formed uniformly on the epitaxial film. Further, by forming the film material 36 having high etching resistance against the carrier gas on the susceptor 32, the generation of hydrocarbon gas due to the reaction between the carbon material and hydrogen is also suppressed. That is, since the carbon / silicon ratio (C / Si) in the gas phase is stabilized and the carrier concentration in the epitaxial film is kept uniform, the epitaxial film can be formed more stably. You will be able to

  As described above, also by the CVD apparatus according to the third embodiment, the effects (1) to (8) according to the first embodiment and the (( In addition to the effect equivalent to or equivalent to the effect of 9), the following effects can be obtained.

  (10) By adopting the above-described configuration as the configuration of the CVD apparatus itself, the substrates 70a and 70b are arranged so that the surface on which the epitaxial film is formed is substantially parallel to the vertical direction. For this reason, even if particles or the like are generated due to the etching of the film material 36, adhesion to the surface of the epitaxial film is suppressed. Furthermore, since at least two substrates 70a and 70b can be disposed on the substrate holder 31, an epitaxial film can be simultaneously formed on the surfaces of these substrates 70a and 70b. In this case, the production efficiency is increased. Will be able to.

(Other embodiments)
The CVD apparatus according to the present invention is not limited to the configurations shown as the first to third embodiments, and can be implemented in the following modes, which are appropriately changed.

  In the first and second embodiments, the semiconductor substrate is rotated in the circumferential direction together with the substrate holder. In particular, in the second embodiment, the susceptor itself provided with the substrate holder is also rotated. However, if the epitaxial film can be uniformly formed on the surface of the semiconductor substrate by adjusting the mounting angle of the substrate and the flow mode of the processing gas, the arrangement of the rotating mechanisms described above can be omitted.

  -Moreover, in these 1st and 2nd embodiment, the upper susceptor (11, 21) and the lower susceptor (12, 22) may be arranged above and below in the direction of gravity, respectively. The arrangement angle is arbitrary. The point is that the processing gas may flow between these susceptors, that is, between the semiconductor substrate and the lower susceptors (12, 22).

Particularly in the first and second embodiments, as described above, a structure in which a semiconductor substrate is installed on the upper susceptor (11, 21) side is certainly desirable. However, the coating of the film material (16, 26) made of the pyrolytic carbon film suppresses the etching of the lower susceptor (12, 22) by the hydrogen gas (H ₂ ), and the generation of particles or the like from the lower susceptor is also possible. When sufficiently suppressed, the semiconductor substrate can be structured to be installed on the lower susceptor side.

  In each of the above embodiments, the film material (16, 26, 36) is formed so as to cover the entire surface of the susceptor (12, 22, 32). ) Need only be formed on the surface facing the semiconductor substrate. In short, at least on the surface facing the semiconductor substrate, if the structure is such that the generation of particles or the like due to the etching of the carbon material is suppressed, the adhesion of these particles and the like to the surface of the semiconductor substrate can be suppressed. .

In each of the above embodiments, the pyrolytic carbon film is used as the film material (16, 26, 36), but a metal carbide film can be used instead. Specific examples of the metal carbide film include tantalum carbide (TaC), dimolybdenum carbide (Mo ₂ C), titanium carbide (TiC), zirconium carbide (ZrC), vanadium carbide (VC), tungsten carbide (WC), and carbonization. Niobium (NbC) can be used, and a film containing at least one of these materials can be used. Such a metal carbide film has a denser structure than the carbon material forming the susceptor (12, 22, 32) to be coated, like the pyrolytic carbon film used in the above embodiments. In addition to being a high-purity material, it is further excellent in heat resistance. For this reason, even when these susceptors (12, 22, 32) are heated to a high temperature, the reactivity between the metal carbide film and hydrogen gas (H ₂ ) can be kept low and the carbon material is etched. The generation of particles and the like is also suppressed, and as a result, a high quality epitaxial film can be formed.

  In each of the above embodiments, the susceptor is heated by high-frequency induction heating, but the heating means is not limited to such high-frequency induction heating. The susceptor may be directly heated by a heater or the like. In short, any structure may be used as long as the semiconductor substrate is uniformly heated by the heat radiation of the heated susceptor so that the epitaxial film can be uniformly formed.

In each of the above embodiments, silane gas (SiH ₄ ) and propane gas (C ₃ H ₈ ) are used as the source gas, but the type of gas is not limited to these. Examples of the silane-based or dichlorosilane-based gas include dichlorosilane gas (SiH ₂ Cl ₂ ), tetrachlorosilane gas (SiCl ₄ ), trichlorosilane gas (SiHCl ₃ ), and the like, and examples of the unsaturated hydrocarbon gas include acetylene gas ( C ₂ H ₂ ), ethylene gas (C ₂ H ₄ ) or the like may be employed.

In each of the above embodiments, a gas containing hydrogen gas (H ₂ ) is used as the carrier gas, and a material having high etching resistance to hydrogen gas (H ₂ ) is used as the film material (16, 26, 36). It was. Instead of this, as the carrier gas, for example, helium gas (He), argon gas (Ar), or the like can be adopted, and in addition to a single gas, a mixed gas in which these are appropriately mixed may be adopted. it can. In that case, what is essential is to use a material having high etching resistance to these carrier gases as the film material (16, 26, 36), thereby suppressing generation of particles or the like due to etching. Will be able to.

In each of the above embodiments, a substrate made of silicon carbide (SiC) is used as the semiconductor substrate, and an epitaxial film made of a silicon carbide (SiC) film is formed on this surface. The CVD apparatus according to the present invention However, the epitaxial film or substrate to be formed (growth) is not limited to this. For example, the CVD apparatus can be used as an apparatus for forming another epitaxial film on the surface of a substrate made of silicon (Si). When a substrate other than silicon carbide (SiC) is employed in this way, the epitaxial film may contain impurities such as boron and aluminum in addition to nitrogen. Even in such a case, in order to control the carrier concentration to “1 × 10 ¹⁶ cm ⁻³ ” or less, the impurity concentration of the background is set to “1 × 10 ¹⁶ cm ⁻³ ” rather than “1 × 10 ¹⁶ cm ⁻³ ”. It is desirable to set it lower than "one digit". In short, the impurity concentration contained in the film material may be “1 ppm” or less with respect to each element.

  In each of the above embodiments, the film material (16, 26, 36) is formed on the surface facing the surface of the semiconductor substrate, but the surface of the susceptor or substrate holder on the side where the semiconductor substrate is installed However, it is desirable that the material has a low impurity concentration. In that sense, it is desirable to form a film material or silicon carbide (SiC) film of the same material as the film material on the surface of the susceptor or substrate holder on the side where these semiconductor substrates are installed.

Sectional drawing which shows the cross-section of the container about 1st Embodiment of the CVD apparatus concerning this invention. Sectional drawing which shows the cross-section of the container about 2nd Embodiment of the CVD apparatus concerning this invention. Sectional drawing which shows the cross-section of the container about 3rd Embodiment of the CVD apparatus concerning this invention. The schematic block diagram which shows the conventional CVD apparatus.

Explanation of symbols

  10, 20, 30 ... container, 11, 21 ... upper susceptor, 12, 22 ... lower susceptor, 22a, 32 ... susceptor, 11a, 21a, 21b, 31a, 31b ... recess, 13, 23a, 23b ... Through hole, 14, 24a, 24b, 31 ... substrate holder, 15, 25a, 25b, 25c ... rotating shaft, 16, 26, 36 ... membrane material, 108 ... gas inflow pipe, 70, 70a, 70b ... semiconductor substrate, 71a 71b, 71c, 71d, 71e ... heat insulating material, 72 ... coil, 100 ... film forming chamber, 101 ... plate, 108a ... tip nozzle, 109 ... gas discharge pipe.

Claims (12)

A susceptor made of a carbon material is provided in the container, and a substrate placed in the container is heated based on the fact that the susceptor is heated, and a carrier gas and a source gas are supplied into the container to supply the surface of the substrate. A CVD apparatus for forming an epitaxial film on
A CVD apparatus, wherein a film material having high etching resistance to the carrier gas is formed on at least a surface of the susceptor facing the substrate. The CVD apparatus according to claim 1, wherein the film material contains carbon. The CVD apparatus according to claim 2, wherein the film material has a denser structure than a carbon material forming the susceptor. The CVD apparatus according to claim 2, wherein the film material is a pyrolytic carbon film. The CVD apparatus according to claim 2, wherein the film material is made of a metal carbide film. The metal carbide film includes tantalum carbide (TaC), dimolybdenum carbide (Mo ₂ C), titanium carbide (TiC), zirconium carbide (ZrC), vanadium carbide (VC), tungsten carbide (WC), and niobium carbide (NbC). The CVD apparatus according to claim 5, comprising a film including at least one of the following. The substrate is a silicon carbide (SiC) substrate, and the CVD apparatus uses a gas containing hydrogen gas (H ₂ ) as the carrier gas, and silane gas (SiH ₄ ) and propane gas (C ₃ H ₈ ) as the source gas. The CVD apparatus according to claim 1, wherein an epitaxial film made of silicon carbide (SiC) is grown on the surface of the substrate. The CVD apparatus according to claim 7,
The nitrogen concentration contained in the film material is 1 ppm or less. The CVD apparatus according to claim 1, wherein the susceptor is heated by high frequency induction heating. The susceptor includes an upper susceptor disposed above the gravitational direction and a lower susceptor disposed below the gravitational direction. The substrate is placed on a substrate holder disposed on the upper susceptor, and the surface thereof is The carrier gas and the source gas flow between the substrate and the lower susceptor, and the film material having high etching resistance to the carrier gas is at least the lower susceptor. The CVD apparatus according to claim 1, wherein the CVD apparatus is formed on a surface facing the substrate. The CVD apparatus according to claim 10, wherein the substrate holder is provided with a rotation mechanism that rotates the substrate in the circumferential direction in a state where the substrate is installed. The substrate is held in a vertical direction by an appropriate substrate holder, and the susceptor is formed in a cylindrical shape so as to cover the surface of the substrate held in the vertical direction, and the carrier gas and the source gas Circulates between the substrate and the susceptor in the vertical direction, and the film material having high etching resistance against the carrier gas is formed on at least the surface of the cylindrical susceptor facing the substrate. The CVD apparatus according to any one of claims 1 to 9.

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