JP2015023043A - Method of manufacturing silicon carbide semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a silicon carbide semiconductor device capable of suppressing variations in film thickness of an oxide film among silicon carbide substrates for products.SOLUTION: An SiC dummy wafer 20 or a silicon wafer, on which a TEOS (Tetraethyl orthosilicate) oxide film or a thermal oxide film is formed by oxidation treatment of a C-plane 20a, is arranged between a SiC monitor wafer 5 and an SiC product wafer 11, and oxidation treatment by an oxidizing gas is performed. In stead of arrangement of the SiC dummy wafer 20 or the silicon wafer, the SiC monitor wafer 5 whose C-plane 5a is subjected to oxidation treatment may be used. A distance between the SiC monitor wafer 5 and the SiC product wafer 11 may be set to a predetermined value or more. An Si-plane 5b of the SiC monitor wafer 5 and an Si-plane 13 of the SiC product wafer 11 may be opposed to each other.

Description

  The present invention relates to a method for manufacturing a silicon carbide semiconductor device including a step of forming an oxide film on a silicon carbide substrate.

  In the manufacturing process of a silicon carbide semiconductor device using silicon carbide (SiC), an oxide film is formed on a product silicon carbide substrate to be a silicon carbide semiconductor device using, for example, a vertical batch diffusion furnace. In the vertical batch type diffusion furnace, a plurality of product lots including SiC product wafers, which are silicon carbide substrates for products, are introduced into a tube and processed in one batch (for example, see Patent Documents 1 to 4).

  Above and below the product lot, a SiC dummy wafer lot (hereinafter also referred to as “dummy wafer lot”) is installed in order to stably secure a soaking zone in the tube. In addition, a plurality of SiC monitor wafers are installed as monitor silicon carbide substrates between product lots in order to check whether there is a problem in the oxidation state in each batch. After the oxidation process is completed, the film thickness of the oxide film formed on each SiC monitor wafer is measured, and it is confirmed whether or not there is a problem in the formation of the oxide film.

JP 2009-140985 A JP 2001-323372 A JP 2008-166501 A JP 2006-066651 A

The oxidation treatment in the vertical batch diffusion furnace is performed, for example, by dry oxidation in which only an oxidizing gas, for example, oxygen (O ₂ ) gas, is introduced into the tube from the gas introduction line in a heat treatment atmosphere.

  When the oxidation process is performed by dry oxidation, there is a problem that the thickness of the oxide film formed in the SiC product wafer immediately below the SiC monitor wafer is thicker than the SiC product wafers in other zones.

  The objective of this invention is providing the manufacturing method of the silicon carbide semiconductor device which can suppress the dispersion | variation in the film thickness of the oxide film between the silicon carbide substrates for products.

  A method for manufacturing a silicon carbide semiconductor device according to the present invention includes a method for forming an oxide film on a product silicon carbide substrate to be a silicon carbide semiconductor device by forming an oxide film by oxidation treatment with an oxidizing gas. In the oxide film forming step, a plurality of silicon carbide substrates for product and a carbonization for monitoring for confirming the state of the silicon carbide substrate for products are provided in a processing chamber into which the oxidizing gas is introduced. A silicon substrate is arranged and an oxidation process using the oxidizing gas is performed. In the oxide film forming step, a carbon surface is oxidized between the silicon carbide substrate for monitoring and the silicon carbide substrate for product. A treated silicon carbide substrate is disposed, and oxidation treatment with the oxidizing gas is performed.

  A method for manufacturing a silicon carbide semiconductor device according to the present invention also includes a silicon carbide semiconductor device including an oxide film forming step of forming an oxide film on a product silicon carbide substrate to be a silicon carbide semiconductor device by oxidation treatment with an oxidizing gas. The oxide film forming step is a method for monitoring a plurality of product silicon carbide substrates and a state of the product silicon carbide substrate in a processing chamber into which the oxidizing gas is introduced. Arranging a silicon carbide substrate and performing an oxidation treatment with the oxidizing gas. In the oxide film forming step, a silicon substrate is disposed between the silicon carbide substrate for monitoring and the silicon carbide substrate for product. It arrange | positions and performs the oxidation process by the said oxidizing gas, It is characterized by the above-mentioned.

  A method for manufacturing a silicon carbide semiconductor device according to the present invention also includes a silicon carbide semiconductor device including an oxide film forming step of forming an oxide film on a product silicon carbide substrate to be a silicon carbide semiconductor device by oxidation treatment with an oxidizing gas. The oxide film forming step is a method for monitoring a plurality of product silicon carbide substrates and a state of the product silicon carbide substrate in a processing chamber into which the oxidizing gas is introduced. This is a step of arranging a silicon carbide substrate and performing an oxidation treatment with the oxidizing gas, wherein the silicon carbide substrate for monitoring has a carbon surface oxidized.

  A method for manufacturing a silicon carbide semiconductor device according to the present invention also includes a silicon carbide semiconductor device including an oxide film forming step of forming an oxide film on a product silicon carbide substrate to be a silicon carbide semiconductor device by oxidation treatment with an oxidizing gas. The oxide film forming step is a method for monitoring a plurality of product silicon carbide substrates and a state of the product silicon carbide substrate in a processing chamber into which the oxidizing gas is introduced. Arranging the silicon carbide substrate and performing an oxidation treatment with the oxidizing gas. In the oxide film forming step, the monitor silicon carbide substrate and the carbonization for the product adjacent to the monitor silicon carbide substrate are arranged. Arranging the silicon carbide substrate for monitoring and the silicon carbide substrate for product so that the distance to the silicon substrate is equal to or greater than a predetermined value, and performing oxidation treatment with the oxidizing gas And features.

  A method for manufacturing a silicon carbide semiconductor device according to the present invention also includes a silicon carbide semiconductor device including an oxide film forming step of forming an oxide film on a product silicon carbide substrate to be a silicon carbide semiconductor device by oxidation treatment with an oxidizing gas. The oxide film forming step is a method for monitoring a plurality of product silicon carbide substrates and a state of the product silicon carbide substrate in a processing chamber into which the oxidizing gas is introduced. Arranging the silicon carbide substrate and performing an oxidation treatment with the oxidizing gas. In the oxide film forming step, the silicon surface of the monitor silicon carbide substrate and the monitor silicon carbide substrate adjacent to the silicon surface. The silicon carbide substrate for monitoring and the silicon carbide substrate for product are arranged so that the silicon surface of the silicon carbide substrate for product faces each other, and oxidation treatment with the oxidizing gas is performed. The features.

  According to the method for manufacturing a silicon carbide semiconductor device of the present invention, the oxidation reaction of the product silicon carbide substrate due to the substance released from the monitor silicon carbide substrate can be suppressed. Therefore, variation in the thickness of the oxide film between the silicon carbide substrates for products can be suppressed.

It is sectional drawing which shows the arrangement | sequence of the wafer in the manufacturing method of the silicon carbide semiconductor device which is the 1st Embodiment of this invention. It is a figure which shows the structure of the vertical batch type | mold diffusion furnace 1 used with the manufacturing method of the silicon carbide semiconductor device which is the 1st Embodiment of this invention. It is sectional drawing which shows the arrangement | sequence of the wafer in the manufacturing method of the silicon carbide semiconductor device which is the 2nd Embodiment of this invention. It is sectional drawing which shows the arrangement | sequence of the wafer in the manufacturing method of the silicon carbide semiconductor device which is the 3rd Embodiment of this invention. It is sectional drawing which shows the arrangement | sequence of the wafer in the manufacturing method of the silicon carbide semiconductor device which is the 4th Embodiment of this invention. It is a figure which shows the structure of the vertical batch type | mold diffusion furnace 30 used by the premise technique of this invention. It is sectional drawing which shows the state of the SiC monitor wafer 5 vicinity at the time of performing dry oxidation. It is a figure which shows typically the crystal structure of a SiC substrate. It is sectional drawing which shows the state of the SiC monitor wafer 5 vicinity at the time of performing wet oxidation.

<Prerequisite technology>
Before describing the method for manufacturing a silicon carbide semiconductor device of the present invention, a method for manufacturing a silicon carbide semiconductor device of the prerequisite technology of the present invention will be described.

  FIG. 6 is a diagram showing a configuration of a vertical batch diffusion furnace 30 used in the base technology of the present invention. In the base technology, an oxide film is formed on a SiC product wafer 11 to be a silicon carbide semiconductor device using a vertical batch diffusion furnace 30 shown in FIG.

  In the vertical batch type diffusion furnace 30, a plurality of SiC product lots 10 including the SiC product wafer 11 are installed in the tube 2 and processed in one batch. For example, six SiC product lots 10 including 25 SiC product wafers 11, that is, 25 / lot × 6 lots = 150 SiC product wafers 11 are processed in one batch.

An oxidizing gas such as oxygen (O ₂ ) gas or water vapor (H ₂ O) is introduced into the tube 2 from the gas introduction line 3. The oxidizing gas flows down in the tube 2 in a predetermined direction, that is, from the top to the bottom in FIG. The SiC product wafer 11 is accommodated in the tube 2 in a state of being arranged at intervals along the flow direction of the oxidizing gas. Here, “upper” and “lower” refer to the upper and lower sides in the vertical direction in a state where the vertical batch diffusion furnace is installed on the installation surface, respectively.

  The SiC product wafer 11 is arranged such that the carbon surface (C surface) faces downward and the silicon surface (Si surface) faces upward. In the following description, the C surface may be referred to as the back surface and the Si surface may be referred to as the front surface. A TEOS oxide film formed by oxidation treatment using tetraethyl orthosilicate (TEOS) is formed on the C surface, which is the back surface of each SiC product wafer 11.

  A SiC dummy wafer lot (hereinafter also referred to as “dummy wafer lot”) 8 is installed above and below the SiC product lot 10 in order to stably secure a soaking zone in the tube 2. In addition, a plurality of SiC monitor wafers 5, 6, and 7 are installed between the SiC product lots 10 in order to check whether there is any problem in the oxidation state in the batch. After the oxidation process is completed, the film thickness of the oxide film formed on each of the SiC monitor wafers 5, 6 and 7 is measured, and it is confirmed whether or not there is a problem in the formation of the oxide film.

  Each of the SiC monitor wafers 5, 6, and 7 is arranged in the same manner as the SiC product wafer 11 so that the C surface as the back surface faces downward and the Si surface as the surface faces upward. Unlike the SiC product wafer 11, the TEOS oxide film is not formed on the C surface which is the back surface of the SiC monitor wafer.

There are two types of oxidation treatment methods in the vertical batch type diffusion furnace 30: dry oxidation and wet oxidation. In dry oxidation, oxidation treatment is performed by introducing only oxygen (O ₂ ) gas into the tube 2 from the gas introduction line 3 in a heat treatment atmosphere. In the wet oxidation, hydrogen and oxygen are burned to generate water vapor (H ₂ O), and the generated water vapor atmosphere is caused to flow from the gas introduction line 3 into the tube 3 to perform the oxidation treatment.

  When the inventor of the present invention performs an oxidation process by dry oxidation, in the SiC product wafer 11 directly below the SiC monitor wafers 5 and 6 disposed upstream of the SiC product wafer 11 in the flow direction of the oxidizing gas. The phenomenon that the film thickness of the formed oxide film becomes about 5 nm thicker than the SiC product wafer 11 in the other zone occurred. Specifically, the oxide film formed on the SiC product wafer 11 immediately below the SiC monitor wafers 5 and 6 is about 10% thicker than the oxide film formed on the SiC product wafer 11 in the other zone. .

  As a result of examining the cause of this phenomenon, as described above, the TEOS oxide film is formed on the C surface which is the back surface of the SiC product wafer 11, and the C surface which is the back surface of the SiC monitor wafers 5, 6 and 7 is formed. Since the TEOS oxide film is not formed, it is presumed that the above-described phenomenon occurs by the following generation model.

  It is presumed that the oxidation reaction in dry oxidation on the SiC substrate is as shown in the following formula (1). In each equation shown below, “(↑)” means that gas (gas) is generated.

SiC + 2O ₂ = SiO ₂ + CO ₂ (↑) (1)

As shown in the formula (1), carbon dioxide (CO ₂ ) gas is generated with the formation of the silicon dioxide (SiO ₂ ) film. The generated CO ₂ gas is reversibly decomposed at a high temperature in the tube 2 to cause a reaction represented by the following formula (2), and carbon monoxide (CO) gas is discharged and oxygen is again emitted. It is estimated that (O ₂ ) gas is generated.

2CO ₂ = 2CO (↑) + O ₂ (↑) (2)

  FIG. 7 is a cross-sectional view showing a state in the vicinity of the SiC monitor wafer 5 when dry oxidation is performed. FIG. 8 schematically shows the crystal structure of the SiC substrate. The SiC product wafer 11 and the SiC monitor wafer 5 are both SiC substrates.

  In FIG. 8, reference numeral “41” represents a silicon (Si) atom, and reference numeral “42” represents a carbon (C) atom. As shown in FIG. 8, the surface on one side in the thickness direction of the SiC substrate 11 becomes a carbon surface (C surface) 12 from which C atoms 42 are exposed, and the surface on the other side in the thickness direction of the SiC substrate 11 has Si atoms 41. It becomes an exposed silicon surface (Si surface).

As shown in FIG. 7, when the oxide films 32 and 33 are formed by supplying oxygen (O ₂ ) gas to the SiC product wafer 11 and the SiC monitor wafer 5 which are SiC substrates, the reaction of the above formula (1). To generate carbon dioxide (CO ₂ ) gas.

In the silicon surface (Si surface) 13 and the carbon surface (C surface) 12 of the SiC product wafer 11, as shown in FIG. 8, the C surface 12 side has carbon (C) atoms on the surface. It is considered that a large amount of CO ₂ gas is generated. The same applies to the SiC monitor wafer 5 shown in FIG. 7, and it is considered that more CO ₂ gas is generated on the C surface 5a side than on the Si surface 5b side.

As described above, since the TEOS oxide film is not formed on the C surface 5a of the SiC monitor wafer 5, the generation of CO ₂ gas cannot be suppressed, and the reaction of the above formula (2) occurs, and the SiC monitor wafer It is considered that the oxygen concentration increases immediately below the C surface 5 a of 5 as indicated by reference numeral 31. Therefore, in the SiC product wafer 11 directly under the SiC monitor wafer 5, it is considered that the non-uniform oxidation reaction is promoted on the Si surface 13 and the formed oxide film 32 is thickened.

In the SiC product wafer 11, since the TEOS film is formed on the C surface 12 side, generation of CO ₂ gas is suppressed by the TEOS film, and oxygen (O ₂ ) gas is not generated again. it is conceivable that. Therefore, since the non-uniform oxidation reaction in the other SiC product wafers 11 under the SiC product wafer 11 is suppressed, it is considered that the thickness of the oxide film 32 does not change between the SiC product wafers 11.

  Further, if an oxidation reaction by wet oxidation is considered, it is presumed that the reaction of the following formula (3) occurs in a steam atmosphere.

SiC + 2H ₂ O = SiO ₂ + CH ₄ (↑) (3)

FIG. 9 is a cross-sectional view showing a state in the vicinity of SiC monitor wafer 5 when wet oxidation is performed. When wet oxidation is performed, the reaction shown in the above formula (3) occurs, and the SiO ₂ film 35 is formed and methane (CH ₄ ) gas is generated. Since the CH ₄ gas is exhausted without reacting on the SiC product wafer 11 and the SiC monitor wafer 5 as it is, it does not affect the surrounding wafers. Therefore, it is considered that the thickness of the oxide film 35 does not change between the SiC product wafers 11.

  As described above, in wet oxidation, variation in the thickness of the oxide film 35 between the SiC product wafers 11 does not cause a problem, but dry oxidation is preferable from the viewpoint of the reliability of the formed oxide film.

  As described above, the dry oxidation has a problem that the film thickness of the oxide film 32 varies between the SiC product wafers 11. Therefore, in the method for manufacturing a silicon carbide semiconductor device of the present invention, the configurations shown in the following embodiments are employed.

<First Embodiment>
FIG. 1 is a cross-sectional view showing the arrangement of wafers in the method for manufacturing a silicon carbide semiconductor device according to the first embodiment of the present invention. The method for manufacturing a silicon carbide semiconductor device according to the first embodiment of the present invention includes an oxide film forming step. In the oxide film forming step, an oxide film is formed on the product silicon carbide (SiC) substrate, specifically, the SiC product wafer 11 to be a silicon carbide semiconductor device, by oxidation treatment using an oxidizing gas.

  A silicon carbide semiconductor device manufactured by the method for manufacturing a silicon carbide semiconductor device of the present embodiment is, for example, a metal-oxide-semiconductor field effect transistor using silicon carbide (SiC). Abbreviated name: MOSFET).

  The oxide film forming step is, for example, a gate oxide film forming step for forming a gate oxide film of a SiC-MOSFET. The oxide film forming step is performed using a thermal oxidation furnace. A vertical batch diffusion furnace is used as the thermal oxidation furnace.

  FIG. 2 is a diagram showing a configuration of a vertical batch type diffusion furnace 1 used in the method for manufacturing a silicon carbide semiconductor device according to the first embodiment of the present invention. In FIG. 2, the description of the boat 4 shown in FIG. 1 is omitted. The vertical batch type diffusion furnace 1 performs an oxidation treatment with an oxidizing gas in a state where the SiC product wafer 11 is held by the boat 4 shown in FIG.

As described above, there are two types of oxidation treatment methods in the vertical batch type oxidation furnace: dry oxidation and wet oxidation. In this embodiment, dry oxidation is employed in order to improve the reliability of the formed oxide film. An oxidizing gas used for the oxidation treatment by dry oxidation is, for example, oxygen (O ₂ ) gas. The oxidizing gas is not limited to this, and may be ozone (O ₃ ) gas.

  In the vertical batch type diffusion furnace 1, a plurality of SiC product lots 10 including a plurality of SiC product wafers 11 are installed in the tube 2 in the same manner as the vertical batch type diffusion furnace 30 in the base technology shown in FIG. And processed in one batch. For example, one SiC product lot 10 includes 25 SiC product wafers 11. For example, six SiC product lots 10 are processed in one batch. That is, 25 wafers / lot × 6 lots = 150 SiC product wafers 11 are processed in one batch.

An oxidizing gas such as O ₂ gas is introduced into the tube 2 from the gas introduction line 3. The tube 2 corresponds to a processing chamber. The oxidizing gas flows down in the tube 2 in a predetermined direction, for example, a direction from top to bottom toward the paper surface of FIG. A plurality of SiC product wafers 11 are held by the boat 4 in a state of being arranged at intervals from each other along the flow direction of the oxidizing gas, that is, along the vertical direction of the tube 2, and are accommodated in the tube 2. Is done.

  The SiC product wafer 11 is arranged such that the carbon surface (C surface) as the back surface faces downward and the silicon surface (Si surface) as the surface faces upward. A TEOS oxide film formed by oxidation treatment using tetraethyl orthosilicate (TEOS) is formed on the C surface, which is the back surface of each SiC product wafer 11.

  Dummy wafer lots 8 are installed above and below the SiC product lot 10 in order to stably secure a soaking zone in the tube 2. The dummy wafer lot 8 includes a plurality of SiC dummy wafers.

  In addition, a plurality of SiC monitor wafers 5, 6, and 7 are arranged in the boat 4 together with the SiC product wafer 11 and accommodated in the tube 2. The SiC monitor wafers 5, 6, and 7 are installed to confirm whether or not there is a problem with the oxidation state in the batch. After the oxidation process is completed, the film thickness of the oxide film formed on each of the SiC monitor wafers 5, 6 and 7 is measured, and it is confirmed whether or not there is a problem in the formation of the oxide film. SiC monitor wafers 5, 6, and 7 correspond to a silicon carbide substrate for monitoring.

  Each of the SiC monitor wafers 5, 6, and 7 is arranged in the same manner as the SiC product wafer 11 so that the C surface as the back surface faces downward and the Si surface as the surface faces upward. Unlike the SiC product wafer 11, the TEOS oxide film is not formed on the C surface which is the back surface of the SiC monitor wafer.

  In the present embodiment, three SiC monitor wafers 5, 6, and 7 are arranged. Specifically, the three SiC monitor wafers 5, 6, and 7 are an upper SiC monitor wafer (hereinafter sometimes referred to as a “TOP-SiC monitor wafer”) 5 disposed on the top of the tube 2, and the tube 2. A center SiC monitor wafer (hereinafter sometimes referred to as a “CNT-SiC monitor wafer”) 6 disposed at the center of the tube 2 and a bottom SiC monitor wafer (hereinafter referred to as “bottom”) of the tube 2. 7) (sometimes referred to as “BTM-SiC monitor wafer”).

  FIG. 1 shows the state of the top (TOP) zone where the TOP-SiC monitor wafer 5 is installed. Although FIG. 1 shows a portion of the TOP zone of the boat 4, the boat 4 actually extends from the top to the bottom of the tube 2 shown in FIG. 2 and is processed in one batch. All wafers can be held.

  As shown in FIG. 1, in the present embodiment, a SiC dummy wafer 20 with a back surface TEOS film is placed immediately below the TOP-SiC monitor wafer 5 on the boat 4. The back surface TEOS film-attached SiC dummy wafer 20 corresponds to a silicon carbide substrate whose C surface is oxidized, and has a TEOS oxide film formed on the C surface 20a, which is the back surface, by oxidation using tetraethylorthosilicate (TEOS). . The SiC product wafer 11 is arranged below the SiC dummy wafer 20 with the back surface TEOS film.

  Although not shown in FIG. 1, the center zone in which the CNT-SiC monitor wafer 6 in the boat 4 is installed has the same arrangement as the TOP zone, as shown in FIG. The back side TEOS film-attached SiC dummy wafer 20 and the SiC product wafer 11 are arranged.

  By arranging in this way, it is possible to suppress an oxidation reaction caused by a substance released from the C-plane side of the TOP-SiC monitor wafer 5 and the CNT-SiC monitor wafer 6 (hereinafter sometimes referred to as “out diffuse”). it can. Thereby, an oxide film having a uniform film thickness can be formed on the SiC product wafer 11 between the zones. Therefore, variation in the thickness of the oxide film between SiC product wafers 11 can be suppressed.

  The back surface TEOS film-attached SiC dummy wafer 20 only needs to have a TEOS oxide film on the C surface 20a, and the Si surface 20b may or may not have a TEOS oxide film. . That is, an SiC wafer having at least a C surface oxidized may be disposed between the SiC monitor wafers 5 and 6 and the SiC product wafer 11.

  As described above, the SiC monitor wafer 5, 6 and the SiC product wafer 11 are disposed with the SiC wafer having the C surface oxidized and subjected to an oxidation treatment with an oxidizing gas, whereby the SiC monitor wafer 5, 6 can suppress the oxidation reaction caused by the out-diffuse from the C-plane side. Therefore, variation in the thickness of the oxide film between SiC product wafers 11 can be suppressed.

In particular, in the present embodiment, the SiC dummy wafer 20 with the back TEOS film having the TEOS oxide film on the C surface is disposed between the SiC monitor wafers 5 and 6 and the SiC product wafer 11, so that the SiC dummy wafer with the back TEOS film is disposed. Generation of CO ₂ gas from the C-plane of 20 can be suppressed. Therefore, variation in the thickness of the oxide film between SiC product wafers 11 can be more reliably suppressed.

  Instead of the SiC dummy wafer 20 with the back surface TEOS film, a SiC wafer having a thermal oxide film formed by thermal oxidation may be provided on the C surface. Also in this case, the same effect as this embodiment can be obtained. In this case, the SiC wafer may be used for the oxidation process with a thermal oxide film on the Si surface, or may be used for the oxidation process with no thermal oxide film.

Further, a silicon (Si) substrate, specifically, a Si wafer, may be installed in place of the back surface TEOS film-attached SiC dummy wafer 20. Since carbon (C) atoms are not contained in the Si substrate, there is no generation of CO ₂ gas as in the generation model shown in the above formula (2). Therefore, by using the Si substrate, the oxidation reaction due to the out-diffusion can be more reliably suppressed. As a result, a uniform oxide film can be formed on the SiC product wafer 11 between the zones, so that variations in the thickness of the oxide film between the SiC product wafers 11 can be more reliably suppressed.

<Second Embodiment>
FIG. 3 is a cross-sectional view showing the arrangement of the wafers in the method for manufacturing the silicon carbide semiconductor device according to the second embodiment of the present invention. In the present embodiment, instead of the SiC monitor wafers 5 and 6 shown in FIGS. 1 and 2, the SiC monitor wafer 21 with the back surface TEOS film is used as shown in FIG. The back surface TEOS film-attached SiC monitor wafer 21 has a TEOS oxide film on the C surface 21a which is the back surface.

  As described above, in this embodiment, instead of the SiC monitor wafers 5 and 6 in the first embodiment, the SiC wafer 21 in which the C surface is oxidized is installed. As a result, as in the first embodiment, it is possible to suppress the oxidation reaction due to the out-diffusion in the SiC product wafer 11 immediately below the SiC monitor wafer 21. Even in the center zone region, a uniform oxide film can be formed on the SiC product wafer 11 between the zones by performing the same wafer arrangement. Therefore, variation in the thickness of the oxide film between SiC product wafers 11 can be suppressed.

In particular, in the present embodiment, instead of the SiC monitor wafers 5 and 6, the back surface TEOS film-attached SiC monitor wafer 21 having the TEOS oxide film on the C surface 21 a is used, so the C surface 21 a of the back surface TEOS film-attached SiC monitor wafer 21. The generation of CO ₂ gas from can be more reliably suppressed. Therefore, variation in the thickness of the oxide film between SiC product wafers 11 can be more reliably suppressed.

  The back surface TEOS film-attached SiC monitor wafer 21 has the thickness of the oxide film formed after the oxidation process is completed, similarly to the SiC monitor wafers 5, 6, and 7 in the above-described base technology and the first embodiment. The measurement is used to confirm whether or not there is a problem in the formation of the oxide film. Accordingly, in order to accurately measure the thickness of the formed oxide film, the back surface TEOS film-attached SiC monitor wafer 21 is used for the oxidation treatment in a state where the Si surface 21b does not have a TEOS oxide film.

  In another embodiment of the present invention, instead of the back surface TEOS film-attached SiC monitor wafer 21, an SiC wafer having a thermal oxide film formed by thermal oxidation on the C surface may be installed as a monitor wafer. Also in this case, the same effect as this embodiment can be obtained. In this case, for the same reason as the Si surface 21b of the SiC monitor wafer 21 with the backside TEOS film described above, the SiC wafer is used for the oxidation process in a state where the Si surface has no thermal oxide film.

<Third Embodiment>
FIG. 4 is a cross sectional view showing the arrangement of the wafers in the method for manufacturing the silicon carbide semiconductor device according to the third embodiment of the present invention. In the present embodiment, as shown in FIG. 4, one boat slit 4 a between the TOP-SiC monitor wafer 5 and the SiC product wafer 11 is opened, and the TOP-SiC monitor wafer 5 and the SiC product immediately below it are provided. The distance d from the wafer 11 is increased.

  Specifically, the distance d between the TOP-SiC monitor wafer 5 and the SiC product wafer 11 adjacent to the TOP-SiC monitor wafer 5 is not less than a predetermined value (hereinafter sometimes referred to as “set distance”). In addition, the TOP-monitor wafer 5 and the SiC product wafer 11 are arranged, and oxidation treatment with an oxidizing gas is performed.

  More specifically, the distance d between the C surface 5a of the TOP-SiC monitor wafer 5 and the Si surface 13 which is the surface facing the SiC monitor wafer 5 of the TOP-adjacent SiC product wafer 11 is greater than the set distance. Thus, the TOP-SiC monitor wafer 5 and the SiC product wafer 11 are arranged, and oxidation treatment with an oxidizing gas is performed.

  The same applies to the CNT-SiC monitor wafer 6. As for the BTM-SiC monitor wafer 7, since the C surface does not face the SiC product wafer 11, it is not necessary to set the distance d to the SiC product wafer 11 to be equal to or greater than the set distance, and the boat between the SiC product wafer 11 and the BTM-SiC monitor wafer 7. There is no need to open a slit.

  That is, with respect to the SiC monitor wafers 5 and 6 whose C surface faces the Si surface of the SiC product wafer 11, as described above, the SiC monitor is set such that the distance d between the adjacent SiC product wafers 11 is equal to or greater than the set distance. Wafers 5 and 6 and SiC product wafer 11 are arranged and an oxidation process using an oxidizing gas is performed.

  By doing in this way, the oxidation reaction by the out-diffusion in the SiC product wafer 11 directly under the SiC monitor wafer 5 can be suppressed as in the first and second embodiments. As a result, an increase in the oxide film of the SiC product wafer 11 directly under the SiC monitor wafer 5 can be suppressed. Therefore, variation in the thickness of the oxide film between SiC product wafers 11 can be suppressed.

  When the diameter of the SiC product wafer 11 is 4 inches, the distance between the boat slits 4a that are the accommodating portions of the boat 4, that is, the boat pitch width is, for example, 4.76 mm. When one boat slit 4a is opened, a distance of 4.76 × 2 = 9.52 mm is generated between the wafers. Therefore, the set distance may be 9.52 mm.

<Fourth embodiment>
FIG. 5 is a cross sectional view showing the arrangement of the wafers in the method for manufacturing the silicon carbide semiconductor device according to the fourth embodiment of the present invention. In FIG. 5, for easy understanding, portions on the C planes 5 a and 12 side of the TOP-SiC monitor wafer 5 and the SiC product wafer 11 are hatched.

  In the present embodiment, as shown in FIG. 5, the SiC product of the TOP-SiC monitor wafer 5 and the SiC product so that the Si surface 5 b of the TOP-SiC monitor wafer 5 and the C surface 12 of the SiC product wafer 11 face each other. The wafer 11 is placed and an oxidation process using an oxidizing gas is performed.

  By doing so, the oxide film formed on the Si surface 13 of the SiC product wafer 11 is not affected by the C surface 5a of the TOP-SiC monitor wafer 5, so that the first and second implementations are performed. Similarly to the above embodiment, the oxidation reaction due to the out-diffusion in the SiC product wafer 11 immediately below the TOP-SiC monitor wafer 5 can be suppressed. Thereby, an oxide film having a uniform film thickness can be formed on each SiC product wafer 11 between the zones. Therefore, variation in the thickness of the oxide film between SiC product wafers 11 can be suppressed.

  In the present embodiment, other SiC monitor wafers, that is, the CNT-SiC monitor wafer 6 and the BTM-SiC monitor wafer 7, as well as the TOP-SiC monitor wafer 5, The SiC monitor wafers 6 and 7 and the SiC product wafer 11 are arranged so as to face the C surface 12 of the SiC product wafer 11, and an oxidation process using an oxidizing gas is performed.

  Thereby, in the SiC product wafer 11 adjacent to the CNT-SiC monitor wafer 6 and the BTM-SiC monitor wafer 7, the oxidation reaction due to out-diffusion can be suppressed. Therefore, variation in the thickness of the oxide film between SiC product wafers 11 can be more reliably suppressed.

  In the present embodiment, the plurality of SiC product wafers 11 are arranged such that the C surface 12 and the Si surface 13 are alternately directed to the TOP-SiC monitor wafer 5 side. In other words, the plurality of SiC product wafers 11 are arranged between the adjacent SiC product wafers 11 such that the Si surfaces 13 face each other and the C surfaces 12 face each other.

  By arranging in this way and performing oxidation treatment with an oxidizing gas, the oxide film formed on the Si surface 13 of each SiC product wafer 11 is affected by the C surface 12 of the adjacent SiC product wafer 11. Nothing will happen. Thereby, an oxide film having a more uniform film thickness can be formed on each SiC product wafer 11 between the zones. Therefore, variation in the thickness of the oxide film between SiC product wafers 11 can be more reliably suppressed.

In each of the embodiments described above, the SiC product wafer 11 is subjected to an oxidation process using an oxidizing gas in a state where the C surface 12 is oxidized. In this way, by performing oxidation treatment with an oxidizing gas in a state where the C surface 12 of the SiC product wafer 11 is oxidized, generation of CO ₂ gas from the C surface 12 of the SiC product wafer 11 can be suppressed. Therefore, variation in the thickness of the oxide film between the SiC product wafers 11 can be more reliably suppressed.

  As shown in FIG. 5 described above, when a plurality of SiC product wafers 11 are arranged so that the C surface 12 and the Si surface 13 alternately face the SiC monitor wafer 5 side, The oxidation treatment with an oxidizing gas may be performed in a state where the C surface 12 is not oxidized.

  As described above, a plurality of SiC product wafers 11 are arranged on the Si surface 13 of each SiC product wafer 11 by arranging the C surface 12 and the Si surface 13 alternately toward the SiC monitor wafer 5 side. The influence of the C surface 12 of the adjacent SiC product wafer 11 on the formed oxide film can be suppressed. Therefore, even if the SiC product wafer 11 is oxidized with an oxidizing gas while the C surface 12 is not oxidized, the thickness of the oxide film formed varies between the SiC product wafers 11. Can be prevented.

  Thus, the degree of freedom of the manufacturing process can be increased by performing the oxidation treatment with the oxidizing gas on the SiC product wafer 11 in a state where the C surface 12 is not oxidized. Therefore, the manufacturing process of the silicon carbide semiconductor device using SiC product wafer 11 can be simplified, and the manufacturing cost can be reduced.

  The present invention can be freely combined with each embodiment within the scope of the invention. In addition, any component in each embodiment can be changed or omitted as appropriate.

  1,30 Vertical batch type diffusion furnace, 2 tube, 3 gas introduction line, 4 boat, 5 upper SiC monitor wafer (TOP-SiC monitor wafer), 5a, 12, 20a, 21a carbon surface (C surface), 5b, 13, 20b, 21b Silicon surface (Si surface), 6 Center SiC monitor wafer (CNT-SiC monitor wafer), 7 Bottom SiC monitor wafer (BTM-SiC monitor wafer), 8 Dummy wafer lot, 10 SiC product lot, 11 SiC product wafer, 20 SiC dummy wafer with backside TEOS film, 21 SiC monitor wafer with backside TEOS film, 32, 33, 35 Oxide film, 41 Silicon (Si) atom, 42 Carbon (C) atom.

Claims (12)

A method of manufacturing a silicon carbide semiconductor device including an oxide film forming step of forming an oxide film by oxidation treatment with an oxidizing gas on a product silicon carbide substrate to be a silicon carbide semiconductor device,
The oxide film forming step includes
A plurality of the product silicon carbide substrates and a monitor silicon carbide substrate for confirming the state of the product silicon carbide substrate are arranged in a processing chamber into which the oxidizing gas is introduced, and the oxidizing properties are arranged. It is a process of oxidizing with gas,
In the oxide film forming step,
A silicon carbide semiconductor, wherein a silicon carbide substrate having a carbon surface oxidized is disposed between the monitor silicon carbide substrate and the product silicon carbide substrate, and oxidation treatment with the oxidizing gas is performed. Device manufacturing method.   2. The carbonized substrate according to claim 1, wherein the silicon carbide substrate having the carbon surface oxidized has a TEOS oxide film formed on the carbon surface by an oxidation treatment using tetraethyl orthosilicate (TEOS). 3. A method for manufacturing a silicon semiconductor device.   2. The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the silicon carbide substrate having the carbon surface oxidized has a thermal oxide film formed by thermal oxidation on the carbon surface. A method of manufacturing a silicon carbide semiconductor device including an oxide film forming step of forming an oxide film by oxidation treatment with an oxidizing gas on a product silicon carbide substrate to be a silicon carbide semiconductor device,
The oxide film forming step includes
A plurality of the product silicon carbide substrates and a monitor silicon carbide substrate for confirming the state of the product silicon carbide substrate are arranged in a processing chamber into which the oxidizing gas is introduced, and the oxidizing properties are arranged. It is a process of oxidizing with gas,
In the oxide film forming step,
A method of manufacturing a silicon carbide semiconductor device, comprising: placing a silicon substrate between the silicon carbide substrate for monitoring and the silicon carbide substrate for product, and performing an oxidation treatment with the oxidizing gas. A method of manufacturing a silicon carbide semiconductor device including an oxide film forming step of forming an oxide film by oxidation treatment with an oxidizing gas on a product silicon carbide substrate to be a silicon carbide semiconductor device,
The oxide film forming step includes
A plurality of the product silicon carbide substrates and a monitor silicon carbide substrate for confirming the state of the product silicon carbide substrate are arranged in a processing chamber into which the oxidizing gas is introduced, and the oxidizing properties are arranged. It is a process of oxidizing with gas,
A method for manufacturing a silicon carbide semiconductor device, wherein the silicon carbide substrate for monitoring has a carbon surface oxidized.   The silicon carbide semiconductor device according to claim 5, wherein the silicon carbide substrate for monitoring has a TEOS oxide film formed on the carbon surface by an oxidation process using tetraethyl orthosilicate (TEOS). Method.   7. The method for manufacturing a silicon carbide semiconductor device according to claim 6, wherein the silicon carbide substrate for monitoring has a thermal oxide film formed by thermal oxidation on the carbon surface. A method of manufacturing a silicon carbide semiconductor device including an oxide film forming step of forming an oxide film by oxidation treatment with an oxidizing gas on a product silicon carbide substrate to be a silicon carbide semiconductor device,
The oxide film forming step includes
A plurality of the product silicon carbide substrates and a monitor silicon carbide substrate for confirming the state of the product silicon carbide substrate are arranged in a processing chamber into which the oxidizing gas is introduced, and the oxidizing properties are arranged. It is a process of oxidizing with gas,
In the oxide film forming step,
The monitor silicon carbide substrate and the product silicon carbide substrate so that a distance between the monitor silicon carbide substrate and the product silicon carbide substrate adjacent to the monitor silicon carbide substrate is not less than a predetermined value. And a method of manufacturing a silicon carbide semiconductor device, wherein oxidation treatment with the oxidizing gas is performed. A method of manufacturing a silicon carbide semiconductor device including an oxide film forming step of forming an oxide film by oxidation treatment with an oxidizing gas on a product silicon carbide substrate to be a silicon carbide semiconductor device,
The oxide film forming step includes
A plurality of the product silicon carbide substrates and a monitor silicon carbide substrate for confirming the state of the product silicon carbide substrate are arranged in a processing chamber into which the oxidizing gas is introduced, and the oxidizing properties are arranged. It is a process of oxidizing with gas,
In the oxide film forming step,
The monitor silicon carbide substrate and the product silicon carbide substrate are arranged so that the silicon surface of the monitor silicon carbide substrate faces the silicon surface of the product silicon carbide substrate adjacent to the monitor silicon carbide substrate. A method for manufacturing a silicon carbide semiconductor device, wherein the silicon carbide semiconductor device is disposed and subjected to oxidation treatment with the oxidizing gas.   10. The silicon carbide semiconductor device according to claim 9, wherein the plurality of product silicon carbide substrates are arranged such that carbon surfaces and silicon surfaces alternately face the monitor silicon carbide substrate side. Production method.   The silicon carbide semiconductor device according to any one of claims 1 to 9, wherein the silicon carbide substrate for product is subjected to an oxidation treatment with the oxidizing gas in a state in which a carbon surface is subjected to an oxidation treatment. Manufacturing method.   The method for manufacturing a silicon carbide semiconductor device according to claim 10, wherein the silicon carbide substrate for product is subjected to an oxidation treatment with the oxidizing gas in a state where a carbon surface is not oxidized.

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