JP2010278210A - Method for forming silicon carbide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a silicon carbide film capable of making a silicon carbide device and a silicon device coexist on a single chip without etching a silicon carbide film having difficulty in etching. <P>SOLUTION: This method for forming the silicon carbide film 13 includes: a step for forming a mask 15a at a position covering a part of a silicon film 14 on a substrate 11 having the silicon film 14 on a surface layer, and a step for applying carbonizing treatment to the silicon film 14 of a region where the mask 15a is not formed to form the silicon carbide film 13 containing the carbonized film. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a silicon carbide film.

  In recent years, silicon carbide has attracted attention as a wide band gap semiconductor material for high voltage power devices such as rectifiers and inverters. Silicon carbide has a characteristic that it has a strong dielectric breakdown electric field and can have a high breakdown voltage, and is excellent in mechanical strength, heat resistance, and chemical stability. Silicon carbide having such characteristics is also expected as a material for MEMS (Micro Electro Mechanical Systems).

  As a method for producing silicon carbide, there are a sublimation recrystallization method using a silicon carbide seed crystal and a CVD method. In the sublimation recrystallization method, an ultra-high temperature treatment around 1700 ° C. is necessary, so that it is difficult to efficiently produce a silicon carbide film at low cost and cope with an increase in diameter. In addition, when a silicon carbide film is manufactured on a silicon oxide film by a CVD method, the modified silicon carbide film locally grows into nuclei and becomes a lump, resulting in a sparse silicon carbide film with a rough surface state. . In the case of a sparse silicon carbide film, it is difficult to form a structure using this film and to form a multilayer structure of various materials on this film, and it becomes difficult to manufacture a good MEMS.

  Various techniques for solving such problems have been studied. For example, Patent Documents 1 and 2 disclose a method using an SOI substrate as a method for manufacturing silicon carbide. In this method, a single-crystal silicon carbide layer on the surface of the SOI substrate is converted into a single-crystal silicon carbide by heat-treating the SOI substrate while supplying a mixed gas of hydrogen gas and hydrocarbon gas into a deposition chamber containing the SOI substrate. It is a method of transforming into a film. Further, in Patent Document 3, a SiCOI substrate is manufactured by transferring a single crystal silicon carbide film onto a support substrate having a silicon oxide film formed on the surface using a transfer technique such as a smart cut method (registered trademark). A method is disclosed.

JP 2002-363551 A JP 2003-224248 A JP 2005-537678 A

In the techniques of Patent Documents 1 to 3, it is considered that the silicon carbide film can be efficiently manufactured, but there are also the following problems.
In Patent Documents 1 and 2, since the single crystal silicon layer has a dense crystal structure, it is necessary to reduce the thickness of the single crystal silicon layer to a thickness of several nanometers in order to carbonize it satisfactorily. This is because if single crystal silicon that is not carbonized remains, defects are generated in the silicon carbide crystal due to a difference in physical property values (for example, lattice constant and thermal expansion coefficient) between the single crystal silicon layer and the silicon carbide film. Since it is difficult to reduce the thickness of the single crystal silicon layer to a thickness of several nm with high accuracy, it is difficult to control the thickness of the resulting silicon carbide film. In Patent Document 3, since a single crystal silicon carbide substrate is used as a substrate to which a silicon carbide film is transferred, the cost is high and it is difficult to cope with an increase in diameter.

On the other hand, there is a demand for a technique in which a device using silicon carbide and a conventional device using silicon are mixedly mounted on one chip. In order to mix a silicon carbide device and a silicon device on one chip, it is necessary to etch the silicon carbide. However, silicon carbide is very stable in bonding and requires a strong etchant, which makes it difficult to etch. For example, in wet etching, molten potassium hydroxide (KOH) having a temperature of several hundred degrees Celsius is used. However, since the temperature is very high, the cost for safety management is high and it is not mass-produced. In dry etching, fluorocarbon (CF) gas, chlorine (Cl ₂ ) gas, and sulfur hexafluoride (SF 6) gas have been developed, but the etching rate is small and the productivity is poor. Furthermore, in dry etching, there is no mask material with a high selection ratio, and there is no optimum base film for etching stop, so it is difficult to etch the silicon carbide film.

  The present invention has been made in view of such circumstances, and a silicon carbide device and a silicon device can be easily mixed on one chip without etching a silicon carbide film which is difficult to etch. An object of the present invention is to provide a method for manufacturing a silicon carbide film.

In order to solve the above problems, a method for manufacturing a silicon carbide film according to the present invention includes a step of forming a mask at a position partially covering the silicon film on a substrate having a silicon film as a surface layer, and the mask is formed. And a step of carbonizing the silicon film in a non-existing region to form a silicon carbide film including the carbonized film.
According to this manufacturing method, since the silicon film in the region where the mask is not formed is carbonized, the silicon film in the region where the mask is formed remains as it is without being carbonized. Therefore, it is possible to easily mix a silicon carbide device and a silicon device on one chip without etching a silicon carbide film that is difficult to etch. In addition, since a single-crystal silicon carbide substrate is not used as in Patent Document 3, it is possible to reduce costs and cope with an increase in the diameter of the substrate used for the base.

This manufacturing method may include a step of thinning the silicon film in a region where the mask is not formed before the step of forming the silicon carbide film.
According to this manufacturing method, since the silicon film is thinned to a predetermined thickness, it can be transformed into a silicon carbide film with almost no silicon film remaining by carbonization. For this reason, a crystal defect of the silicon carbide film due to a difference in lattice constant and thermal expansion coefficient between the silicon film remaining without being carbonized and the silicon carbide film does not occur. Therefore, crystal defects in the silicon carbide film can be suppressed, and a silicon carbide film with good crystallinity can be manufactured.

In this manufacturing method, it is desirable that the silicon film includes at least one of single crystal silicon, amorphous silicon, and polysilicon.
According to this manufacturing method, a silicon carbide film having a thickness corresponding to the thickness of the silicon film including at least one of single crystal silicon, amorphous silicon, and polysilicon can be obtained. When amorphous silicon or polysilicon is used, it is easier to form a silicon film with a predetermined film thickness than, for example, reducing a single crystal silicon layer on an SOI substrate to a predetermined film thickness. A silicon carbide film having an accurate film thickness can be easily manufactured. In addition, since amorphous silicon and polysilicon have a coarser crystal structure (not dense) than single crystal silicon, carbon can be uniformly diffused into the silicon film during carbonization, and the silicon film is carbonized uniformly and satisfactorily. be able to. For this reason, it is avoided that a part of the silicon film remains without being carbonized, and it is possible to prevent a crystal defect from occurring due to a difference in lattice constant and thermal expansion coefficient between the silicon film and the silicon carbide film. Therefore, a silicon carbide film having a dense and uniform film thickness and a desired film thickness can be obtained.

In this manufacturing method, the mask is preferably made of a silicon oxide film.
According to this manufacturing method, since the silicon oxide film is not carbonized by the carbonization process, the silicon oxide film functions as a protective film during the carbonization process so as not to allow carbon to pass through the base. For this reason, it is reliably avoided that the silicon film in the region where the mask is formed is carbonized, and a silicon carbide device and a silicon device can be remarkably easily mixed on one chip.

In this manufacturing method, the mask is preferably made of a silicon nitride film.
According to this manufacturing method, since the silicon nitride film is not carbonized by the carbonization treatment, it functions as a protective film during the carbonization treatment so as not to allow carbon to permeate the base. For this reason, it is reliably avoided that the silicon film in the region where the mask is formed is carbonized, and the silicon carbide device and the silicon device can be remarkably mixed on one chip.

In this manufacturing method, the carbonization treatment in the step of forming the silicon carbide film with the substrate made of silicon may be performed using heat treatment by lamp annealing.
According to this manufacturing method, the rate of temperature increase can be increased in the carbonization treatment in the step of forming the silicon carbide film, and the crystallinity of the silicon carbide film can be improved.

In the present manufacturing method, the substrate is made of silicon or quartz, and the carbonization treatment in the step of forming the silicon carbide film may be performed using a heat treatment by furnace annealing.
According to this manufacturing method, since a large number of substrates can be heat-treated at once by furnace annealing, a large number of silicon films formed on a large number of substrates can be carbonized together. Therefore, as the number of substrates to be carbonized at once is increased, the time for forming the silicon carbide film per substrate can be shortened, and the manufacturing efficiency can be increased.

In this manufacturing method, the silicon film may be formed using a CVD method.
According to this manufacturing method, the crystallinity of the silicon film can be lowered by setting the film formation temperature in the process of forming the silicon film low, and at least one of amorphous silicon and polysilicon is easily included. A silicon film can be formed. Further, according to the CVD method, a silicon film with a high accuracy can be formed. By carbonizing the silicon film, a silicon carbide film with a high accuracy can be manufactured.

In the present manufacturing method, it is desirable that the thickness of the silicon film is 100 nm or less.
The inventor of the present application has found that when the film thickness of the silicon film is 100 nm or less, the carbonization can be transformed into a silicon carbide film with almost no silicon film remaining. According to this manufacturing method, crystal defects of the silicon carbide film due to the difference in lattice constant and thermal expansion coefficient between the silicon film remaining without being carbonized and the silicon carbide film do not occur. Therefore, crystal defects in the silicon carbide film can be suppressed, and a silicon carbide film with good crystallinity can be manufactured.

In this manufacturing method, after the silicon carbide film is formed, the carbonized film may be used as a seed layer to epitaxially grow silicon carbide to increase the thickness.
According to this manufacturing method, a dense and uniform film quality seed layer is formed. Therefore, when silicon carbide is epitaxially grown using the carbonized film as a seed layer, a dense and uniform film quality silicon carbide film is manufactured. can do. Therefore, a silicon carbide film having a dense and uniform film quality and a desired film thickness can be obtained.

The manufacturing method may include a step of forming a compound semiconductor film on the silicon carbide film after the step of forming the silicon carbide film.
According to this manufacturing method, a silicon carbide film having a dense and uniform film quality is formed. Therefore, when a compound semiconductor film is formed by lattice matching with the silicon carbide film, a compound semiconductor film having good crystallinity can be obtained. it can.

It is a schematic diagram which shows the structure of the semiconductor substrate of 1st Embodiment. It is a figure which shows the manufacturing process of the semiconductor substrate of 1st Embodiment. FIG. 3 is a diagram showing a semiconductor substrate manufacturing process following FIG. 2; It is a schematic diagram which shows the structure of the semiconductor substrate of 3rd Embodiment. It is a figure which shows the manufacturing process of the semiconductor substrate of 3rd Embodiment. It is a schematic diagram which shows the structure of the semiconductor substrate of 4th Embodiment. It is a figure which shows the manufacturing process of the semiconductor substrate of 4th Embodiment. FIG. 8 is a diagram illustrating a manufacturing step of the semiconductor substrate following that of FIG. 7; It is a schematic diagram which shows the structure of the semiconductor substrate of 5th Embodiment. It is a figure which shows the manufacturing process of the semiconductor substrate of 5th Embodiment. FIG. 11 is a diagram illustrating manufacturing steps of the semiconductor substrate following FIG. 10;

  Embodiments of the present invention will be described below with reference to the drawings. This embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each structure easy to understand, an actual structure and a scale, a number, and the like in each structure are different.

(First embodiment)
FIG. 1 is a diagram schematically showing a configuration of a semiconductor substrate 10 having a silicon carbide film 13 in the first embodiment of the present invention. As shown in FIG. 1, a semiconductor substrate 10 is a substrate (silicon substrate) 11 made of silicon, a silicon oxide film 12, a silicon carbide film 13, and a silicon film 14 containing amorphous silicon (hereinafter referred to as an amorphous silicon film). ).

  The silicon substrate 11 is a substrate serving as a base for the silicon oxide film 12, the silicon carbide film 13, and the amorphous silicon film 14. The silicon substrate 11 is formed by slicing and polishing a silicon ingot formed using, for example, the CZ method (Czochralski method) or the FZ method (floating zone method).

  On the silicon oxide film 12, two films of an amorphous silicon film 14 and a silicon carbide film 13 are mixedly formed. The silicon carbide film 13 is formed by carbonizing the amorphous silicon film 14. Since the silicon carbide film 13 has a high band gap value and a strong dielectric breakdown electric field, it can have a high breakdown voltage, and is excellent in mechanical strength, heat resistance, and chemical stability. For this reason, when the semiconductor substrate 10 is used, it is possible to manufacture a good high voltage power device and a good MEMS.

  The silicon oxide film 12 is formed between the silicon substrate 11 and the two films of the amorphous silicon film 14 and the silicon carbide film 13. The film thickness T1 of silicon oxide is about 100 nm, for example. The silicon oxide film 12 prevents the silicon substrate 11 and the two films of the amorphous silicon film 14 and the silicon carbide film 13 from coming into contact with each other. The silicon oxide film 12 functions as a buffer layer that alleviates the difference in lattice constant and thermal expansion coefficient between the silicon substrate 11 and the silicon carbide film 13.

(Semiconductor substrate manufacturing method)
Next, a method for manufacturing the semiconductor substrate 10 having the silicon carbide film 13 according to the present embodiment will be described. 2 and 3 are process diagrams showing the manufacturing process of the semiconductor substrate 10 in order. In the present embodiment, an amorphous silicon film 14 is formed on a silicon substrate 11 via a silicon oxide film 12, and a mask 15a is formed at a position partially covering the amorphous silicon film 14, and the mask 15a is formed. The silicon carbide film 13 is formed by carbonizing the amorphous silicon film 14 in the non-existing region.

  When manufacturing the semiconductor substrate 10, first, as shown in FIG. 2A, a silicon substrate 11 manufactured by a method similar to the conventional method is prepared. Next, the surface layer of the silicon substrate 11 is thermally oxidized. As a result, a silicon oxide film 12 is formed on the surface layer of the silicon substrate 11 as shown in FIG. The film thickness T1 of the silicon oxide film is, for example, about 100 nm.

  As a result, the silicon carbide film 13 does not come into contact with the silicon substrate 11, and the silicon oxide film 12 can function as a buffer layer that alleviates the difference in lattice constant and thermal expansion coefficient between the silicon substrate 11 and the silicon carbide film 13. . As a result, crystal defects in the silicon carbide film 13 can be suppressed, and the silicon carbide film 13 having a dense and uniform film quality can be manufactured. In addition, when a device is manufactured by forming an element on the silicon carbide film 13 obtained by this manufacturing method, the device can be completely divided using the silicon oxide film 12, so that a device with low power consumption can be obtained.

  Next, as shown in FIG. 2C, an amorphous silicon film 14 is formed on the silicon oxide film 12 by a CVD method. In the CVD method, the lower the substrate temperature, the lower the crystallinity of the resulting film, and an amorphous silicon film can be obtained. According to the CVD method, it is possible to form the amorphous silicon film 14 having a high precision film thickness.

  In this embodiment, the amorphous silicon film thickness (silicon film thickness) T2 is set to about 30 nm. Thereby, crystal defects of the silicon carbide film 13 due to the difference in lattice constant and thermal expansion coefficient between the amorphous silicon film 14 remaining without being carbonized and the silicon carbide film 13 do not occur. This is because the inventor of this application can change the film thickness T2 of the amorphous silicon film to 100 nm or less, so that the amorphous silicon film 14 can be transformed into the silicon carbide film 13 with almost no amorphous silicon film 14 remaining under the silicon carbide film 13 by the carbonization process. By finding out.

  Next, as shown in FIG. 2D, the surface layer of the amorphous silicon film 14 is thermally oxidized to form a silicon oxide film 15 on the surface layer of the amorphous silicon film 14. Next, as shown in FIG. 3A, a mask 15a is formed at a position covering a part of the amorphous silicon film 14 by patterning the silicon oxide film 15 using wet etching using a conventional photolithography technique. To do. The region where the mask 15a is formed is a region where the amorphous silicon film 14 remains. In other words, the region where the mask 15a is formed is a region where the silicon carbide film 13 is not formed.

  Next, as shown in FIG. 3B, carbonization is performed using a mask 15a to carbonize the amorphous silicon film 14 in a region where the mask 15a is not formed. Thereby, the amorphous silicon film 14 in the region where the mask 15a is formed remains as it is without being carbonized. That is, silicon carbide film 13 is selectively formed in a region where mask 15a is not formed.

The carbonization treatment of the amorphous silicon film 14 is performed using an infrared heating type lamp annealing apparatus. The carbonization treatment may be performed, for example, in a mixed gas atmosphere composed of a hydrocarbon gas such as propane gas (C ₃ H ₈ ) and a hydrogen gas at a substrate temperature of 800 to 1400 ° C. Note that the carbonization treatment of this embodiment is performed under the conditions of a substrate temperature of 1160 ° C. and a treatment time of 60 seconds by monitoring the substrate temperature from the back side of the substrate. Heating with a lamp annealing device can increase the rate of temperature rise of the substrate temperature when forming the silicon carbide film 13 and the amorphous silicon film 14 can be heated to a higher temperature than the silicon substrate 11. The crystallinity of the silicon film 13 can be improved.

  Further, since the amorphous silicon film 14 is amorphous, carbon can be diffused more uniformly in the amorphous silicon film 14 than a film made of a single crystal. Further, since the film thickness T2 of the amorphous silicon film is set to 100 nm or less (here, 30 nm), carbon can be distributed in the amorphous silicon film 14 and the amorphous silicon film 14 can be almost completely carbonized. As described above, since the amorphous silicon film 14 is formed with a highly accurate film thickness, the silicon carbide film 13 having a desired film thickness can be obtained. Further, since the amorphous silicon film 14 can be carbonized well, the silicon carbide film 13 having a fine and uniform film quality with few crystal defects can be obtained.

  Next, as shown in FIG. 3C, the mask 15a on the amorphous silicon film 14 is removed by wet etching. An etchant used for this wet etching is, for example, a diluted hydrogen fluoride aqueous solution. Through the above steps, the semiconductor substrate 10 having the silicon carbide film 13 of the present embodiment can be manufactured.

  According to the method for manufacturing the silicon carbide film 13 of the present embodiment, the amorphous silicon film 14 in the region where the mask 15a is not formed is carbonized, so the amorphous silicon film 14 in the region where the mask 15a is formed is not carbonized. It remains as it is. Therefore, it is possible to easily mix a silicon carbide device and a silicon device on one chip without etching the silicon carbide film 13 that is difficult to etch. In addition, since a single crystal silicon carbide substrate is not used as in Patent Document 3, it is possible to reduce the cost and cope with an increase in the diameter of the substrate used for the base.

  Moreover, according to this manufacturing method, the silicon carbide film 13 having a film thickness corresponding to the film thickness T2 of the amorphous silicon film is obtained. Forming the amorphous silicon film 14 to a predetermined thickness is easier than, for example, reducing the thickness of the single crystal silicon layer on the SOI substrate to a predetermined thickness. 13 can be easily manufactured. In addition, since amorphous silicon has a coarser crystal structure (not dense) than single crystal silicon, carbon can be uniformly diffused into the amorphous silicon film 14 in the carbonization process, and the amorphous silicon film 14 can be carbonized uniformly and satisfactorily. can do. For this reason, it is avoided that a part of the amorphous silicon film 14 remains without being carbonized, and the occurrence of crystal defects due to the difference in lattice constant and thermal expansion coefficient between the amorphous silicon film 14 and the silicon carbide film 13 is prevented. Is done. Therefore, a silicon carbide film 13 having a dense and uniform film thickness and a desired film thickness can be obtained.

  Further, according to the present manufacturing method, the mask 15a is made of the silicon oxide film 15, and the silicon oxide film 15 is not carbonized by the carbonization process, and thus functions as a protective film during the carbonization process so as not to allow carbon to permeate the base. For this reason, it is reliably avoided that the amorphous silicon film 14 in the region where the mask 15a is formed is carbonized, and a silicon carbide device and a silicon device can be remarkably easily mixed on one chip. .

  Further, according to this manufacturing method, the carbonization treatment in the step of forming the silicon carbide film 13 using the silicon substrate 11 as the base substrate is performed using a heat treatment by lamp annealing. Thereby, the rate of temperature rise can be increased in the carbonization treatment in the step of forming silicon carbide film 13, and the crystallinity of silicon carbide film 13 can be improved.

  Further, according to the present manufacturing method, since the amorphous silicon film 14 is formed using the CVD method, the crystal of the amorphous silicon film 14 is set by setting the film forming temperature low in the step of forming the amorphous silicon film 14. The amorphous silicon film 14 can be easily formed. Further, according to the CVD method, it is possible to form the amorphous silicon film 14 with a high precision film thickness, and by carbonizing this, it becomes possible to manufacture the silicon carbide film 13 with a high precision film thickness. .

  Further, according to this manufacturing method, since the film thickness T2 of the amorphous silicon film is 100 nm or less, the lattice constant and the thermal expansion coefficient of the amorphous silicon film 14 and the silicon carbide film 13 that remain without being carbonized are different. This prevents the occurrence of crystal defects in the silicon carbide film 13. This is because the inventor of this application can change the film thickness T2 of the amorphous silicon film to 100 nm or less, so that the amorphous silicon film 14 can be transformed into the silicon carbide film 13 with almost no amorphous silicon film 14 remaining under the silicon carbide film 13 by the carbonization process. By finding out. Therefore, crystal defects in silicon carbide film 13 can be suppressed, and silicon carbide film 13 with good crystallinity can be manufactured.

  In addition, although the process of forming the silicon carbide film 13 according to the present embodiment is performed using heat treatment by lamp annealing, it is not limited to this. For example, the step of forming the silicon carbide film 13 may be performed using heat treatment by laser annealing.

  In this manufacturing method, the silicon oxide film is formed as a buffer layer between the substrate and the silicon carbide film before the step of forming the silicon carbide film, but the present invention is not limited to this. For example, a silicon nitride film may be formed as a buffer layer between the substrate and the silicon carbide film.

(Second embodiment)
Next, the configuration of the semiconductor substrate 20 having the silicon carbide film 23 according to the second embodiment of the present invention will be described using FIG. 1 in the same manner as the semiconductor substrate 10 according to the first embodiment. As shown in FIG. 1, the semiconductor substrate 20 includes a substrate (quartz substrate) 21 made of quartz, a silicon oxide film 12, a silicon carbide film 23, and a polysilicon film 24. On the silicon oxide film 12, two films of a polysilicon film 24 and a silicon carbide film 23 are formed in a mixed manner. The semiconductor substrate 20 of the present embodiment has a point that the substrate 21 is made of quartz, a point that the substrate 21 is made of a silicon film 24 containing polysilicon (hereinafter referred to as a polysilicon film), and a silicon carbide film 23 that carbonizes the polysilicon film 24. It differs from the semiconductor substrate 10 described in the first embodiment in that it is formed.

(Semiconductor substrate manufacturing method)
Next, a method for manufacturing the semiconductor substrate 20 having the silicon carbide film 23 according to the present embodiment will be described with reference to FIGS. 2 and 3 as in the manufacturing process according to the first embodiment. In the present embodiment, a polysilicon film 24 is formed on the quartz substrate 21 via the silicon oxide film 12, and a mask 25a is formed at a position partially covering the polysilicon film 24, and this mask 25a is formed. The polysilicon film 24 in the non-existing region is carbonized to form a silicon carbide film 23.

  When manufacturing the semiconductor substrate 20, first, as shown in FIG. 2A, a quartz substrate 21 manufactured by a method similar to the conventional method is prepared. Next, a silicon-oxidized film is formed on the quartz substrate 21 by using, for example, a thermal CVD method. As a result, the silicon oxide film 12 is formed on the quartz substrate 21 as shown in FIG. The film thickness T1 of the silicon oxide film is, for example, about 100 nm.

  Next, as shown in FIG. 2C, the amorphous silicon film 14 is crystallized on the silicon oxide film 12 using thermal annealing or laser annealing to form a polysilicon film 24. Thus, by using polysilicon as the silicon film 24, it becomes easier to form a film as compared with single crystal silicon, and the film thickness can be easily controlled.

  In this embodiment, the film thickness (silicon film thickness) T2 of the polysilicon film is set to about 30 nm. As a result, the crystal defect of the silicon carbide film 23 due to the difference in lattice constant and thermal expansion coefficient between the polysilicon film 24 and the silicon carbide film 23 that remain without being carbonized does not occur. This is because the inventor of the present application can change the thickness of the polysilicon film T2 to 100 nm or less so that the polysilicon film 24 can be transformed into the silicon carbide film 23 with almost no polysilicon film 24 remaining under the silicon carbide film 23 by the carbonization process. By finding out.

  Next, as shown in FIG. 2D, a silicon nitride film 25 is formed on the surface layer of the polysilicon film 24 by CVD. Next, as shown in FIG. 3A, the silicon nitride film 25 is patterned by dry etching using a conventional photolithography technique to form a mask 25a at a position covering a part of the polysilicon film 24. Next, as shown in FIG. To do.

  Next, as shown in FIG. 3B, carbonization is performed using a mask 25a to carbonize the polysilicon film 24 in a region where the mask 25a is not formed. As a result, the polysilicon film 24 in the region where the mask 25a is formed remains as it is without being carbonized. That is, the silicon carbide film 23 is selectively formed in a region where the mask 25a is not formed.

The carbonization of the polysilicon film 24 is performed by furnace annealing using an electric furnace or the like. The carbonization treatment may be performed, for example, under a condition of a substrate temperature of 800 to 1400 ° C. in an atmosphere of a mixed gas composed of a hydrocarbon gas such as C ₃ H ₈ and hydrogen gas. In addition, the carbonization process of this embodiment is performed on conditions with a substrate temperature of 1250 ° C. and a processing time of 15 minutes. When heated by furnace annealing, a large number of quartz substrates 21 can be heat-treated in a lump, so that a large number of polysilicon films 24 formed on a large number of quartz substrates 21 can be carbonized together.

  Further, since the film thickness T2 of the polysilicon film is set to 100 nm or less (here, 30 nm), carbon can be spread in the polysilicon film 24, and the polysilicon film 24 can be almost completely carbonized. As described above, since the polysilicon film 24 is formed with a highly accurate film thickness, the silicon carbide film 23 having a desired film thickness can be obtained. Further, since the polysilicon film 24 can be carbonized satisfactorily, a silicon carbide film 23 having a fine and uniform film quality with few crystal defects can be obtained.

  Next, as shown in FIG. 3C, the mask 25a made of the silicon nitride film 25 on the polysilicon film 24 is removed by hot phosphoric acid treatment. The semiconductor substrate 20 having the silicon carbide film 23 of this embodiment can be manufactured through the above steps.

  According to the method for manufacturing the silicon carbide film 23 of the present embodiment, the silicon carbide film 23 having a thickness corresponding to the thickness T2 of the polysilicon film is obtained. Forming the polysilicon film 24 to a predetermined film thickness is easier than, for example, reducing the thickness of the single crystal silicon layer on the SOI substrate to a predetermined film thickness. 23 can be easily manufactured. For this reason, it is avoided that a part of the polysilicon film 24 remains without being carbonized, and a crystal defect is prevented from being caused by the difference in lattice constant and thermal expansion coefficient between the polysilicon film 24 and the silicon carbide film 23. Is done. Therefore, a silicon carbide film 23 having a dense and uniform film thickness and a desired film thickness can be obtained.

  Further, according to the present manufacturing method, the mask 25a is made of the silicon nitride film 25, and the silicon nitride film 25 is not carbonized by the carbonization process. Therefore, carbonization of the polysilicon film 24 in the region where the mask 25a is formed is surely avoided, and a silicon carbide device and a silicon device can be remarkably mixed on one chip. .

  Further, according to the present manufacturing method, the carbonization treatment in the step of forming the silicon carbide film 23 using the quartz substrate 21 as the base substrate is performed using a heat treatment by furnace annealing. Since many quartz substrates 21 can be collectively heat-treated by furnace annealing, a large number of polysilicon films 24 formed on many quartz substrates 21 can be carbonized together. Therefore, as the number of quartz substrates 21 to be carbonized at once is increased, the deposition time of the silicon carbide film 23 per quartz substrate 21 can be shortened, and the production efficiency can be increased.

(Third embodiment)
Next, the configuration of the semiconductor substrate 10A having the silicon carbide film 13H according to the third embodiment of the present invention will be described with reference to FIG. This diagram schematically shows a configuration of a semiconductor substrate 10A having a silicon carbide film 13H according to the third embodiment, corresponding to FIG. The semiconductor substrate 10A of this embodiment is different from the semiconductor substrate 10 described in the first embodiment described above in that the silicon carbide film 13H is formed by thickening by epitaxial growth. Since the other points are the same as in the first embodiment, the same elements as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 4, the semiconductor substrate 10 </ b> A includes a silicon substrate 11, a silicon oxide film 12, a silicon carbide film 13 </ b> H thickened by epitaxial growth, and an amorphous silicon film 14. On the silicon oxide film 12, two films of an amorphous silicon film 14 and a thickened silicon carbide film 13H are mixedly formed. The film thickness of the thickened silicon carbide film 13 </ b> H is larger than the film thickness of the amorphous silicon film 14.

(Semiconductor substrate manufacturing method)
Next, a method for manufacturing the semiconductor substrate 10A having the silicon carbide film 13H according to the present embodiment will be described. FIG. 5 is a process chart showing the manufacturing process of the semiconductor substrate 10A step by step. In the present embodiment, the amorphous silicon film 14 in the region where the mask 15a is not formed on the silicon substrate 11 is carbonized to form a seed layer 13a, and silicon carbide is epitaxially grown on the seed layer 13a to epitaxial layer 13b. As a result, a silicon carbide film 13H is formed. Note that an amorphous silicon film 14 is formed on the silicon substrate 11 via the silicon oxide film 12, and a mask 15a is formed at a position partially covering the amorphous silicon film 14 (FIGS. 2A to 3D). The steps up to a)) are the same as those in the first embodiment described above, and thus detailed description thereof is omitted.

  When manufacturing the semiconductor substrate 10A, first, as shown in FIG. 5A, carbonization is performed using a mask 15a to carbonize the amorphous silicon film 14 in a region where the mask 15a is not formed. Thereby, the amorphous silicon film 14 in the region where the mask 15a is formed remains as it is without being carbonized. That is, the seed layer 13a is selectively formed in a region where the mask 15a is not formed.

  The carbonization process of the amorphous silicon film 14 is performed using an infrared heating type lamp annealing apparatus, as in the first embodiment. Thereby, the crystallinity of the seed layer 13a can be improved. Moreover, since the amorphous silicon film 14 is formed with a highly accurate film thickness as in the first embodiment, the seed layer 13a having a desired film thickness can be obtained. Further, a dense and uniform seed layer 13a with few crystal defects can be obtained.

  Next, as shown in FIG. 5B, silicon carbide is epitaxially grown on the seed layer 13a to form an epitaxial layer 13b. Epitaxial growth may be performed, for example, in a mixed gas atmosphere consisting of hydrogen gas and silicon carbide gas, at a processing temperature of 500 to 1500 ° C. Thereby, silicon carbide in the mixed gas can be grown on the seed layer 13a, and the epitaxial layer 13b having the crystal structure of the seed layer 13a can be formed. Thereby, silicon carbide film 13H having seed layer 13a and epitaxial layer 13b is obtained. Since the seed layer 13a has a dense and uniform film quality, the epitaxial layer 13b obtained by epitaxially growing silicon carbide based on the seed layer 13a also has a dense and uniform film quality.

  Next, as shown in FIG. 5C, the mask 15a made of silicon oxide 15 on the amorphous silicon film 14 is removed by wet etching. Through the above steps, the semiconductor substrate 10A having the silicon carbide film 13H of the present embodiment can be manufactured.

  According to the method for manufacturing the silicon carbide film 13H of the present embodiment, the seed layer 13a having a dense and uniform film quality is formed. Therefore, when silicon carbide is epitaxially grown using the carbonized film as a seed layer 13a, the seed layer 13a is dense. Thus, a silicon carbide film 13H having a uniform film quality can be manufactured. Therefore, a silicon carbide film 13H having a dense and uniform film quality and a desired film thickness can be obtained.

  In the manufacturing method of this embodiment, the amorphous silicon film 14 in the region where the mask 15a made of the silicon oxide film 15 on the silicon substrate 11 is not formed is carbonized to form the seed layer 13a, and the seed layer 13a The semiconductor substrate 10A having the silicon carbide film 13H is manufactured by epitaxially growing silicon carbide thereon to form the epitaxial layer 13b. However, the present invention is not limited to this.

  For example, a quartz substrate 21 may be used instead of the silicon substrate 11, or a mask 25 a made of a silicon nitride film 25 may be used instead of the mask 15 a made of the silicon oxide film 15. In this manner, the polysilicon film 24 in the region where the mask 25a made of the silicon nitride film 25 on the quartz substrate 21 is not formed is carbonized to form the seed layer 23a, and silicon carbide is formed on the seed layer 23a. The semiconductor substrate 20A having the silicon carbide film 23H may be manufactured by epitaxial growth to form the epitaxial layer 23b.

  In this manufacturing method, a silicon film containing amorphous silicon or polysilicon is formed on a substrate, but the present invention is not limited to this. For example, a laminated film of an amorphous silicon film and a polysilicon film may be formed as a silicon film. That is, a silicon film including at least one of amorphous silicon and polysilicon may be formed.

  In this manufacturing method, the silicon oxide film or the silicon nitride film is formed as a buffer layer between the substrate and the silicon carbide film before the step of forming the silicon carbide film, but the present invention is not limited to this. For example, a silicon carbide film may be formed on the upper surface of the substrate without forming a buffer layer between the substrate and the silicon carbide film.

  In this manufacturing method, the silicon film is formed using the CVD method, but the present invention is not limited to this. For example, a silicon film may be formed using a sputtering method or coating.

  In the present manufacturing method, the film thickness of the silicon film is about 30 nm. However, the thickness is not limited to this, and can be 100 nm or less. This is because the inventor of the present application has found that the silicon film can be transformed into a silicon carbide film without any silicon remaining in the carbonization process by making the film thickness of the silicon film 100 nm or less.

  In the present manufacturing method, when a silicon film containing amorphous silicon or polysilicon is carbonized, it is performed under conditions of a processing temperature of 800 to 1400 ° C. Thereby, amorphous silicon or polysilicon is recrystallized and crystallization proceeds. As a result, the inventors of the present application speculate that the silicon carbide film can be more crystalline than the silicon film before carbonization.

(Fourth embodiment)
Next, the configuration of the semiconductor substrate 30 having the silicon carbide film 33 according to the fourth embodiment of the present invention will be described with reference to FIG. This diagram schematically shows the configuration of the semiconductor substrate 30 having the silicon carbide film 33 according to the fourth embodiment, corresponding to FIG. The semiconductor substrate 30 of this embodiment is different from the semiconductor substrate 10 described in the first embodiment in that a silicon carbide film 33 is formed using an SOI substrate.

  As shown in FIG. 6, a semiconductor substrate 30 includes a silicon substrate 31, a silicon oxide film 32, a surface active silicon film 34, and a silicon carbide film 33 that has been carbonized by partially thinning the surface active silicon film 34. And is configured. In other words, the semiconductor substrate 30 includes a silicon carbide film 33 that has been carbonized by partially thinning the surface active silicon film 34 of the SOI substrate including the silicon substrate 31, the silicon oxide film 32, and the surface active silicon film 34. have. On the silicon oxide film 32, two films of a surface active silicon film 34 and a silicon carbide film 33 are mixedly formed.

(Semiconductor substrate manufacturing method)
Next, a method for manufacturing the semiconductor substrate 30 having the silicon carbide film 33 according to the present embodiment will be described. 7 and 8 are process diagrams showing the manufacturing process of the semiconductor substrate 30 in order. In the present embodiment, the silicon carbide film 33 is formed by thinning a part of the surface active silicon film 34 of the SOI substrate and performing carbonization.

  When manufacturing the semiconductor substrate 30, first, as shown in FIG. 7A, an SOI substrate including a silicon substrate 31, a silicon oxide film 32, and a surface active silicon film 34 is prepared. Next, the surface layer of the surface active silicon film 34 of the SOI substrate is thermally oxidized. As a result, a silicon oxide film 35 is formed on the surface layer of the surface active silicon film 34.

  Next, as shown in FIG. 7B, a silicon nitride film 36 is formed on the silicon oxide film 35 by, eg, CVD. Next, as shown in FIG. 7C, a part of the silicon oxide film 35 on the surface active silicon film 34 is formed by patterning the silicon nitride film 36 by dry etching using a conventional photolithography technique. A mask 36a is formed at the covering position.

  Next, as shown in FIG. 7D, thermal oxidation is performed using a mask 36a to oxidize the surface active silicon film 34 in a region where the mask 36a is not formed. This oxidation treatment is preferably performed to such an extent that the film thickness of the surface active silicon film 34 in the region where the mask 36a is not formed becomes 10 nm or less. In the present embodiment, the thickness of the surface active silicon film 34 in the region where the mask 36a is not formed is about 5 nm.

  Next, as shown in FIG. 8A, wet etching is performed using a mask 36a to remove the silicon oxide film 35 in a region where the mask 36a is not formed. As a result, the surface active silicon film 34 thinned to a predetermined thickness is exposed in a region where the mask 36a is not formed. Further, a mask 35a made of the silicon oxide film 35 is formed in the same pattern as the mask 36a at a position overlapping the mask 36a. Next, as shown in FIG. 8B, thermal phosphoric acid treatment is performed to remove the mask 36a made of the silicon nitride film 36 on the mask 35a.

  Next, as shown in FIG. 8C, carbonization is performed using a mask 35a to carbonize the surface active silicon film 34 in a region where the mask 35a is not formed. As a result, the surface active silicon film 34 in the region where the mask 35a is formed remains as it is without being carbonized. That is, the silicon carbide film 33 is selectively formed in a region where the mask 35a is not formed. Further, as described above, since the surface active silicon film 34 in the region where the mask 35a is not formed is thinned to a predetermined thickness, the surface active silicon film 34 is almost below the silicon carbide film 33 by carbonization. The silicon carbide film 33 can be transformed without remaining.

  Next, as shown in FIG. 8D, the mask 35a made of the silicon oxide film 35 on the surface active silicon film 34 is removed by wet etching. Through the above steps, the semiconductor substrate 30 having the silicon carbide film 33 of the present embodiment can be manufactured.

  According to the method for manufacturing the silicon carbide film 33 of the present embodiment, the surface active silicon film 34 is thinned to a predetermined thickness, so that the surface active silicon film 34 is almost left under the silicon carbide film 33 by carbonization. Without being transformed into the silicon carbide film 33. Therefore, crystal defects of silicon carbide film 33 due to the difference in lattice constant and thermal expansion coefficient between surface active silicon film 34 and silicon carbide film 33 that remain without being carbonized do not occur. Therefore, crystal defects of silicon carbide film 33 can be suppressed, and silicon carbide film 33 with good crystallinity can be manufactured.

(Fifth embodiment)
Next, the configuration of the semiconductor substrate 30A according to the fifth embodiment of the present invention will be described with reference to FIG. This diagram schematically shows a configuration of a semiconductor substrate 30A according to the fifth embodiment corresponding to FIG. The semiconductor substrate 30A of this embodiment is different from the semiconductor substrate 30 described in the fourth embodiment in that the transistor 50 is formed on the surface active silicon film 34. Since the other points are the same as in the fourth embodiment, the same elements as those in FIG. 6 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 9, the semiconductor substrate 30 </ b> A includes a transistor 50 provided on the surface active silicon film 34 and an insulating film 39 made of silicon oxide provided to cover the transistor 50. . An element isolation region 38a is provided on the surface layer of the surface active silicon film 34, and the space between the element isolation regions 38a corresponds to one transistor region.

  The transistor 50 is provided on both sides of the gate insulating film 51 provided on the surface active silicon film 34, the gate electrode 52 provided on the gate insulating film 51, and the gate electrode 52 in the surface layer of the surface active silicon film 34. The source region 53 and the drain region 54, and a side wall 55 provided on the side surface of the gate electrode 52 are configured. With the above structure, when a voltage is applied to the gate electrode 52 of the transistor 50, a channel is formed and a current can flow between the source region 53 and the drain region 54.

(Semiconductor substrate manufacturing method)
Next, a method for manufacturing the semiconductor substrate 30A having the transistor 50 according to the present embodiment will be described. 10 and 11 are process diagrams sequentially showing the manufacturing process of the semiconductor substrate 30A. In the present embodiment, an element isolation region 38a is formed on the surface layer of the surface active silicon film 34, a transistor 50 is formed on the surface active silicon film 34 between the element isolation regions 38a, and an insulating film 39 covering the transistor 50 is formed. To do. A process of removing the silicon oxide film 35 in a region where the mask 36a is not formed by preparing an SOI substrate and thermally oxidizing it, and performing wet etching using the mask 36a (FIGS. 7A to 8A). )) Is the same as in the fourth embodiment described above, and detailed description thereof is omitted.

  When manufacturing the semiconductor substrate 30A, first, as shown in FIG. 10A, carbonization is performed using a mask 36a to carbonize the surface active silicon film 34 in a region where the mask 36a is not formed. As a result, the surface active silicon film 34 in the region where the mask 36a is formed remains as it is without being carbonized. That is, the silicon carbide film 33 is selectively formed in a region where the mask 36a is not formed.

  Next, as shown in FIG. 10B, a mask 36a made of silicon nitride and a mask 35a made of silicon oxide are patterned into a mask 36b and a mask 35b having predetermined patterns, respectively, using a conventional photolithography technique. Next, as shown in FIG. 10C, etching is performed using a mask 36b to form a groove corresponding to a portion to be an element isolation region 38a in the surface active silicon film 34. Next, as shown in FIG.

  Next, as shown in FIG. 10D, an insulating layer 38 made of silicon oxide is formed so as to cover the entire exposed portions of the silicon carbide film 33, the surface active silicon film 34, and the mask 36b on the silicon substrate 31. . Next, as illustrated in FIG. 11A, the element isolation region 38 a is formed by polishing and planarizing the insulating layer 38 on the silicon substrate 31 using CMP (Chemical Mechanical Polishing).

  Next, as shown in FIG. 11B, thermal phosphoric acid treatment is performed using the element isolation region 38a as a mask, and the mask 36b made of the silicon nitride film 36 on the mask 35b is removed. Next, the mask 35b is removed using wet etching, and the gate insulating film 51 is formed by thermal oxidation. Next, a gate electrode 52 made of polycrystalline silicon is formed on the gate insulating film 51. Next, the sidewall 55 is formed using, for example, an etch back method. Next, impurities are implanted into the surface layer of the surface active silicon film 34 between the element isolation region 38 a and the gate electrode 52 to form the source region 53 and the drain region 54. Through the above steps, the transistor 50 having the gate insulating film 51, the gate electrode 52, the source region 53, the drain region 54, and the sidewall 55 is formed on the surface active silicon film 34.

  Next, as shown in FIG. 11C, an insulating film 39 is formed on the silicon substrate 31 on which the transistor 50 is formed by depositing silicon oxide by, for example, a CVD method. Next, as shown in FIG. 11D, the insulating film 39 and part of the element isolation region 38a on the silicon carbide film 33 are removed by etching. Through the above steps, the semiconductor substrate 30A having the transistor 50 of the present embodiment can be manufactured.

  In the manufacturing method of this embodiment, a device (transistor 50) is selectively formed on the surface active silicon film 34, but the present invention is not limited to this. For example, a device may be formed on the silicon carbide film 33. By forming a device on the silicon carbide film 33, a high breakdown voltage device can be obtained. The step of forming a device on the silicon carbide film 33 may be performed after the step of removing the insulating film 39 and the element isolation region 38a on the silicon carbide film 33 by etching (FIG. 11D). Alternatively, it may be performed after the step of carbonizing the surface active silicon film 34 in the region where the mask 36a is not formed (FIG. 10A). Various wirings may be formed on the silicon carbide film 33.

  In this manufacturing method, after the step of forming the silicon carbide film, the method may include a step of epitaxially growing silicon carbide using the carbonized film as a seed layer to increase the thickness, or on the silicon carbide film. You may have the process of forming a compound semiconductor film. As a material for forming the compound semiconductor film, for example, gallium nitride (GaN), aluminum nitride (AlN), zinc oxide (ZnO), boron nitride (BN), or aluminum gallium nitride (AlGaN) can be used.

  According to this manufacturing method, a silicon carbide film having a dense and uniform film quality is formed. Therefore, when a compound semiconductor film is formed by lattice matching with the silicon carbide film, a compound semiconductor film having good crystallinity can be obtained. it can.

DESCRIPTION OF SYMBOLS 11, 31 ... Silicon substrate (substrate), 12, 32, 35 ... Silicon oxide film, 13, 13H, 23, 23H, 33 ... Silicon carbide film, 13a, 23a ... Seed layer, 14 ... Amorphous silicon film (silicon film) , 15a, 25a, 35a, 35b, 36a, 36b ... mask, 21 ... quartz substrate (substrate), 25, 36 ... silicon nitride film, 24 ... polysilicon film (silicon film), 34 ... surface active silicon film (silicon film) ), T2... Amorphous silicon film thickness, polysilicon film thickness (silicon film thickness)

Claims (12)

Forming a mask at a position partially covering the silicon film on the substrate having a silicon film as a surface layer;
And carbonizing the silicon film in a region where the mask is not formed to form a silicon carbide film including the carbonized film.   2. The method of manufacturing a silicon carbide film according to claim 1, further comprising a step of thinning the silicon film in a region where the mask is not formed before the step of forming the silicon carbide film.   The method for manufacturing a silicon carbide film according to claim 1, wherein the silicon film includes at least one of amorphous silicon and polysilicon.   The method for manufacturing a silicon carbide film according to claim 1, wherein the silicon film includes single crystal silicon.   The method for manufacturing a silicon carbide film according to claim 1, wherein the mask is made of a silicon oxide film.   The method for manufacturing a silicon carbide film according to claim 1, wherein the mask is made of a silicon nitride film.   The silicon carbide film according to claim 1, wherein the substrate is made of silicon, and the carbonization treatment in the step of forming the silicon carbide film is performed using a heat treatment by lamp annealing. Production method.   The silicon carbide according to claim 1, wherein the substrate is made of silicon or quartz, and the carbonization treatment in the step of forming the silicon carbide film is performed using a heat treatment by furnace annealing. A method for producing a membrane.   The method for producing a silicon carbide film according to claim 1, wherein the silicon film is formed by a CVD method.   The method for manufacturing a silicon carbide film according to claim 1, wherein the thickness of the silicon film is 100 nm or less.   11. The method according to claim 1, further comprising a step of forming a thick film by epitaxially growing silicon carbide using the carbonized film as a seed layer after forming the silicon carbide film. A method for manufacturing a silicon carbide film.   The method for producing a silicon carbide film according to claim 1, further comprising a step of forming a compound semiconductor film on the silicon carbide film after the step of forming the silicon carbide film. .

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