JP2005311352A - Method of forming oxide film, semiconductor device, method and apparatus for manufacturing the semiconductor device, method of oxidizing silicon carbide substrate, and silicon carbide mos semiconductor device and silicon carbide mos integrated circuit using the method, and apparatus for manufacturing the silicon carbide mos semiconductor device and silicon carbide mos integrated circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a high-quality chemical oxide film on the surface of a semiconductor, at low voltage and at low temperature. <P>SOLUTION: While immersing a silicon substrate 1 to be processed in an oxidizing solution 3 in a processing bath 2, the silicon substrate 1 is connected to a power supply 4. While applying a voltage between the silicon substrate 1 and a counter electrode 5 in the processing bath 2, the oxidizing solution 3, such as nitric acid, is made to react with the silicon substrate 1 so that a silicon dioxide film 15 is formed on the surface of the silicon substrate 1. In this process, growth of the silicon dioxide film 15 occurs at the interface between the silicon substrate 1 and the silicon dioxide film 15 (that is, the surface of the silicon substrate 1). Consequently, the thickness of the silicon dioxide film 15 can be controlled arbitrarily while being at a low voltage and a low temperature so that the high-quality silicon dioxide film 15 can be formed easily on the surface of the silicon substrate 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for forming an oxide film, a method for manufacturing a semiconductor device, and a device for manufacturing a semiconductor device. For example, a metal-oxide-semiconductor device used in a semiconductor integrated circuit, that is, a MOS (Metal Oxide- Semiconductor oxide film formation method for forming a high-quality silicon dioxide film (insulating film) with a desired thickness on the surface of a semiconductor, particularly a silicon substrate, at a low temperature and a low voltage, and manufacturing a semiconductor device The present invention relates to a method and a semiconductor device manufacturing apparatus. The present invention also includes a method of oxidizing a SiC substrate for forming a silicon dioxide film having a good interface state at a low temperature in a short time on a silicon carbide (SiC) substrate, a SiCMOS type semiconductor device using the same, and the same. The present invention relates to an SiC-MOS type integrated circuit, an SiC-MOS type semiconductor device, and an apparatus for manufacturing an SiC-MOS type integrated circuit.

  In semiconductor devices, especially semiconductor integrated circuits using MOS transistors, it is important to improve the performance of insulating films used for the miniaturization of circuit elements accompanying higher integration and higher density.

  In this type of semiconductor integrated circuit, the gate insulating film of a MOS transistor is usually formed by a so-called high temperature thermal oxidation method in which heat treatment is performed at a high temperature of 800 ° C. or higher in an oxidizing gas such as dry oxygen or water vapor.

  In addition to the high temperature thermal oxidation method, chemical vapor deposition (CVD) method in which an organic silane such as tetraethoxysilane (TEOS) is thermally decomposed at several hundred degrees Celsius and an oxide film is deposited on the substrate is sputtered. Oxide film forming methods such as sputtering deposition method by vapor deposition and plasma oxidation method for oxidizing a substrate surface in plasma are well known.

  In addition, as an anodic oxidation method that oxidizes the substrate surface by anodic oxidation to form an oxide film, for example, a voltage is applied to the silicon substrate in an electrolyte hydrofluoric acid aqueous solution to form a porous anodic reaction film of silicon. Then, a method of anodizing the porous anodic reaction film in an electrolyte capable of anodizing silicon such as concentrated phosphoric acid is known (see, for example, Patent Documents 1 to 3 and Non-Patent Documents 1 and 2). ).

  In anodic oxidation, silicon ions on the silicon substrate are moved to the surface of the silicon dioxide film by applying a voltage, and a silicon dioxide film is formed on the surface of the silicon substrate. Then, silicon ions are generated from the silicon substrate for the purpose of causing an oxidation reaction to proceed at the interface between the silicon dioxide film and the electrolyte (the surface of the silicon dioxide film). Furthermore, in order for the silicon ions to permeate through the silicon dioxide film and lead to the interface between the silicon dioxide film and the electrolyte (the surface of the silicon dioxide film), it is usually necessary to apply a large voltage of 100 V or more (non-patent document). 2).

  On the other hand, the present inventor has proposed a chemical oxide film forming method for chemically forming an oxide film instead of an electrochemical oxide film forming method by applying a voltage (Patent Documents 4 to 7, Non-Patent Document 3). ~ 4). For example, it has been proposed to form a thin oxide film of about 1 nm on the surface of a semiconductor substrate such as silicon using a highly oxidizing chemical solution such as concentrated nitric acid (Patent Document 4).

  By the way, in recent years, silicon carbide (SiC) has attracted attention for its excellent physical properties such as wide gap, breakdown electric field, saturation electron velocity, and thermal conductivity, and its application to semiconductor devices such as power devices and high-frequency devices has begun. ing.

  Similar to Si, SiC can form an oxide film (silicon dioxide film) by thermal oxidation. For this reason, if SiC is applied to a power MOSFET (power device), it is possible to significantly reduce the on-resistance (heat loss) as well as to greatly reduce the size of the system (Non-patent Document 5).

  Even in this case, in order to set the thickness of the gate oxide film at the time of design to, for example, 10 nm or more by thermal oxidation, a high temperature treatment at 1100 ° C. or more for several hours is required. In addition, the interface state of the oxide film formed by high-temperature thermal oxidation is extremely large, and the original characteristics of the SiC-MOSFET cannot be exhibited.

Therefore, in order to establish a basic technology for device application, it is strongly desired to improve processes such as lowering the temperature of the oxide film formation, shortening the time, and reducing the interface state of the oxide film.
Japanese Patent Laid-Open No. 3-6826 (published January 14, 1991) Japanese Laid-Open Patent Publication No. 52-78374 (released July 1, 1977) JP 2003-133309 A (published May 9, 2003) JP 2004-47935 A (published February 12, 2004) Japanese Laid-Open Patent Publication No. 9-45679 (published February 14, 1997) JP 2002-57154 A (published February 22, 2002) JP 2002-64093 (published February 28, 2002) Applied Physics Vol. 44, No. 5, 497-506, 1975 Complete Electronics Technology MOS Device (1973 First Edition) by Tokuyama Satoshi, pages 124-125 J. Applied Physics Letters, 81, 18, pp3410-3412 (2002) J. Applied Physics Letters, 94, 11, pp7328-7335 (2003) Applied physics 2005.3. (Vol.74 No.3 pp371-375)

However, in the conventional anodic oxidation method, a high voltage (usually 100 V or more) is required in order to release the semiconductor component ions to be oxidized from the semiconductor surface and to guide the semiconductor component ions to the oxide film surface. Specifically, in the anodic oxidation method, the growth of the silicon dioxide film (oxide film) on the surface of the silicon substrate in the electrolyte is performed by using silicon ions (Si ⁺ ) on the silicon substrate from the interface between the silicon substrate and the silicon dioxide film. Then, it passes through the silicon dioxide film and moves to the silicon dioxide film surface (silicon dioxide film-electrolyte interface), and the oxidation reaction proceeds on the silicon dioxide film surface. Therefore, it is necessary to increase the voltage applied to the silicon substrate as the silicon dioxide film is formed and the film thickness increases. However, if the voltage is increased too much, it causes a leakage current, and it is difficult to form a high-quality silicon dioxide film with good controllability.

  In addition, in the anodic oxidation method, ions in the electrolytic solution are mixed into the oxide film, so it is difficult to obtain a high-quality oxide film. Moreover, in the anodic oxidation method, since the oxidation reaction proceeds on the surface of the silicon dioxide film, the surface of the silicon dioxide film formed first becomes the silicon dioxide / silicon substrate interface. Since silicon dioxide is formed while maintaining the initial interface (the interface remains unchanged), it is difficult to obtain excellent interface characteristics. In addition, in anodic oxidation, silicon ions are released from the silicon substrate, so that porous is formed on the surface of the silicon substrate. For this reason, for example, the stability of electrical characteristics is also insufficient. Therefore, in order to maintain the target quality by the oxide film formed by the anodic oxidation method, it is necessary to increase the thickness of the oxide film.

  On the other hand, in the method of Patent Document 4 proposed by the present inventors, although a high-quality oxide film is formed, the thickness of the silicon dioxide film actually formed by a highly oxidizing chemical solution is about 1.5 nm. No more film thickness was obtained.

  Also, other conventional oxide film formation methods, for example, after removing a natural oxide film on the surface of a silicon substrate, an ultrathin oxide film (chemical oxide film) having a thickness of nanometers (nm) or less. However, the quality of the oxide film is not controlled so that it can be used as an insulating film of a semiconductor device. In particular, it is difficult to obtain an oxide film having a small leakage current density. For example, in particular, a gate insulating film of a thin film transistor (TFT) is required to form a relatively thick oxide film of several nanometers (nm) or more on the silicon substrate surface in order to maintain a withstand voltage.

  In addition, when forming a thin film transistor (TFT) on a flexible substrate used in a liquid crystal display, for example, a substrate such as polyethylene terephthalate (PET), it is necessary to keep the temperature of the substrate at 200 ° C. or lower. It is.

  Therefore, even in such a low-temperature manufacturing process, it is required to form a high-quality insulating film that can be used in a semiconductor device, such as a gate insulating film of a TFT.

  The present invention has been made in view of the above-described conventional problems, and the object thereof is not a high voltage exceeding 100 V, which is applied in the conventional anodic oxidation, but a low-voltage and high-quality chemical oxide film ( In particular, an oxide film forming method, a semiconductor device manufacturing method using the oxide film, and a semiconductor device manufacturing apparatus capable of realizing a silicon dioxide film) are provided.

  Furthermore, another object of the present invention is to form a gate insulating film when a thin film transistor (TFT) is formed on a substrate such as the PET or when a MOS transistor or a large scale integrated circuit (LSI) using the MOS transistor is formed. It is possible to form a high-quality oxide film with low leakage current density characteristics, etc. that can be used for semiconductors on the surface of a semiconductor while controlling the thickness at a low temperature that can be formed on a substrate such as PET. An object of the present invention is to provide a method for forming an oxide film, a method for manufacturing a semiconductor device using the method for forming an oxide film, and a device for manufacturing the semiconductor device.

  Another object of the present invention is to provide a technique capable of forming a silicon dioxide film having a good interface state at a low temperature in a short time on the surface of a SiC substrate.

  In order to solve the above problems, an oxide film forming method (present forming method) of the present invention includes an oxide film forming step of forming a chemical oxide film on a semiconductor surface in a state where a voltage is applied to the semiconductor. In the film forming method, the oxide film forming step is characterized in that the chemical oxide film is formed on the semiconductor surface by allowing an oxidizing solution or a gas thereof to act on the semiconductor.

  According to the above configuration, by applying an oxidizing solution or a gas thereof (hereinafter referred to as “oxidizer”) to a semiconductor while a voltage is applied to the semiconductor, an oxidizing species (ion) is generated from the oxidizing agent. Or radical). Further, since a voltage is applied to the semiconductor, oxidized species are introduced to the semiconductor surface. When the oxidized species reach the semiconductor surface, the semiconductor component is oxidized by the oxidized species to form a chemical oxide film. That is, the chemical oxide film is an oxide of a semiconductor component. As described above, the oxide film forming step is a step in which an oxidizing species (ion or radical) generated from the oxidizing solution or its gas is guided to the semiconductor surface and a chemical oxide film is grown on the semiconductor surface. That is, in the oxide film forming step, voltage application to the semiconductor is performed to introduce oxidized species to the semiconductor surface, not to ionize the semiconductor component. Therefore, in the present forming method, a large voltage necessary for ionizing the semiconductor component is not required, so that a chemical oxide film can be formed under a low voltage condition.

  According to the above configuration, the semiconductor is oxidized to form a chemical oxide film, so that the semiconductor becomes thinner and the chemical oxide film on the semiconductor surface becomes thicker as the oxidation reaction proceeds. That is, in the above configuration, the semiconductor itself is oxidized rather than newly depositing an oxide film on the semiconductor surface. For this reason, even if the semiconductor surface is uneven, it is possible to reliably form a chemical oxide film having a uniform thickness.

  In particular, this forming method is characterized in that a chemical oxide film is formed on the semiconductor surface. In other words, after the chemical oxide film is formed on the semiconductor surface, the chemical oxide film is formed (grown) on the semiconductor surface (interface between the semiconductor and the chemical oxide film). For this reason, in this formation method, an oxidant that passes through the chemical oxide film and can move to the semiconductor surface is used. Therefore, in this formation method, it is not necessary to introduce semiconductor component ions to the surface of the chemical oxide film. For this reason, this formation method does not require a high voltage of 100 V or more unlike the anodic oxidation method, and an oxide film can be formed with a lower voltage (for example, about 5 to 20 V) lower than 100 V. In addition, in this formation method, unlike patent document 1, it is not necessary to form a porous film | membrane on the semiconductor surface.

  On the other hand, in the conventional anodic oxidation method, ions of semiconductor components are guided to the surface of the chemical oxide film, and a chemical oxide film is grown on the surface of the chemical oxide film, so that a high voltage needs to be applied to the semiconductor. In particular, high voltage is required for ionization of semiconductor components.

  In addition, since this formation method is basically a chemical film formation reaction by applying a voltage to a semiconductor, a chemical oxide film can be formed at a low temperature as in the case of anodic oxidation. Therefore, in the present forming method, since a high voltage and a high temperature are not required, the film quality of the chemical oxide film can be improved, and a high-quality chemical oxide film having a low leakage current density can be formed.

  Furthermore, by applying a voltage, the formation rate of the chemical oxide film can be improved as compared with the case where no voltage is applied. Therefore, a chemical film can be formed in a short time.

  Thus, according to the present forming method, a high-quality chemical oxide film having a desired thickness can be uniformly formed on the semiconductor surface at a low temperature and a low voltage. That is, the quality of the chemical oxide film can be improved, and a high-quality chemical oxide film with a low leakage current density can be formed. Therefore, for example, even if a chemical oxide film is used as the insulating film, the chemical oxide film functions as a high-quality insulating film, and therefore can be made thinner (for example, several nm or less) than the current insulating film.

  In this formation method, an oxidizing agent is used that allows the oxidizing species generated from the oxidizing solution or its gas to pass through the chemical oxide film and move to the semiconductor surface. That is, an oxidizing solution having strong oxidizing power or a gas (oxidant) thereof that generates oxidizing species having strong oxidizing power is used. As a result, the oxidized species permeate the formed chemical oxide film and move to the semiconductor surface (interface between the semiconductor and the chemical oxide film), and the chemical oxide film grows on the semiconductor surface.

  As described above, the “oxidizing solution or gas thereof” forms a chemical oxide film by acting (contacting) a semiconductor, and generates (generates) an oxidizing species capable of oxidizing a semiconductor component. Is. In addition, the above-mentioned “acting the oxidizing solution or its gas” is particularly limited as long as the oxidizing solution or its gas (more specifically, the oxidizing species) is in contact with at least a part of the semiconductor surface. It is not something.

  In the present forming method, the oxide film forming step is preferably performed by immersing the semiconductor to which the voltage is applied in an oxidizing solution. Thereby, an oxide film formation process can be performed with a simple structure of immersing in an oxidizing solution. Therefore, the present invention can be applied particularly when a chemical oxide film is formed on a large (large area) semiconductor. For this reason, since a large-scale apparatus such as a CVD apparatus is unnecessary, the manufacturing cost can be reduced.

  In this formation method, the semiconductor preferably contains silicon, and the chemical oxide film is preferably a silicon oxide film.

  Further, in this formation method, the semiconductor is at least one selected from single crystal silicon, polycrystalline silicon, amorphous silicon, silicon carbide, and silicon-germanium, and the chemical oxide film is a silicon oxide film It is preferable that

  A silicon oxide film (silicon dioxide film) is an oxide film having the widest use range. However, since the film quality is low, a certain degree of film thickness is required to fulfill the function as an oxide film. According to the above configuration, a high-quality silicon oxide film can be uniformly formed on the semiconductor surface. Therefore, the silicon oxide film can be thinned by replacing the conventional silicon oxide film with the above-described silicon oxide film.

  Further, in this forming method, the oxidizing solution or the gas thereof is nitric acid, perchloric acid, sulfuric acid, ozone-dissolved water, hydrogen peroxide solution, a mixed solution of hydrochloric acid and hydrogen peroxide solution, sulfuric acid and hydrogen peroxide solution. From at least one solution selected from the group consisting of: a mixed solution of ammonia water and a hydrogen peroxide solution, a mixed solution of sulfuric acid and nitric acid, aqua regia, and boiling water, its gas, or a mixture thereof It is preferable to become.

  According to said structure, an oxidizing solution or its gas generate | occur | produces the oxidizing species (for example, oxygen ions, radicals, such as oxygen ion, hydroxide ion, peroxide ion) with strong oxidizing power. For this reason, by using the semiconductor on which the chemical oxide film is to be formed as the anode, it is possible to guide these oxidized species to the semiconductor surface even after the chemical oxide film is formed.

  In the present forming method, the oxidizing solution or the gas thereof is preferably an azeotropic mixture having an azeotropic concentration or more, more preferably an azeotropic mixture with water, and an azeotropic mixture with water. More preferably, it comprises at least one solution selected from the group of azeotropic nitric acid, azeotropic sulfuric acid that is an azeotrope with water, and azeotropic perchloric acid that is an azeotrope with water, or a gas thereof. . Furthermore, these azeotropes are particularly preferably caused to cause the oxidizing solution or gas thereof heated to the azeotropic temperature or higher to act on the semiconductor.

  According to the above configuration, since the azeotropic mixture is used as the oxidizing solution or the gas, the concentration of the solution and the vapor (that is, the gas) is constant during the formation of the semiconductor chemical oxide film (during the oxide film forming process). become. That is, the azeotropic mixture becomes a constant solution composition / vapor composition by heating to an azeotropic boiling point or higher. Thereby, the growth of the chemical oxide film can be controlled by time management. Therefore, the formation (thickness and quality) of the chemical oxide film can be controlled with higher accuracy.

  The present forming method includes a first step of forming a first chemical oxide film on the semiconductor surface by causing an oxidizing solution or gas thereof having an azeotropic concentration to act on the semiconductor, and the first chemical oxidation. And a second step of forming a second chemical oxide film thicker than the first chemical oxide film by applying an oxidizing solution having an azeotropic concentration or higher to the film, or a gas thereof. And at least one of the first step and the second step is performed on the semiconductor surface by allowing the oxidizing solution or the gas to act on the semiconductor in a state where a voltage is applied to the semiconductor. The structure characterized by forming the chemical oxide film may be used.

  That is, this forming method is characterized in that at least one of the first step and the second step is performed by the oxide film forming step.

  According to the above configuration, since at least one of the first step and the second step is performed in the same manner as the above-described oxide film forming step, a high-quality chemical oxide film having a desired thickness is formed in the same manner as described above. It can be uniformly formed on the semiconductor surface at low temperature and low voltage. That is, the quality of the chemical oxide film can be improved, and a high-quality chemical oxide film with a low leakage current density can be formed. Therefore, for example, even if a chemical oxide film is used as the insulating film, the chemical oxide film functions as a high-quality insulating film, and therefore can be made thinner (for example, several nm or less) than the current insulating film.

  Further, according to the above configuration, the first chemical oxide film thinner than the second chemical oxide film is formed in the first step, and the second thicker than the first chemical oxide film is formed in the second step. A chemical oxide film is formed. In particular, the first chemical oxide film is made to react with the second chemical oxidation because an oxidizing solution or gas thereof having an azeotropic concentration lower than that in the first step and an azeotropic concentration higher than that in the second step are allowed to act. It becomes a chemical oxide film having a lower atomic density than the film. That is, it can be said that the first step is a step of forming a first chemical oxide film having pores. In the second step, the second chemical oxide film is formed by the action of the oxidizing solution or the gas on the pores present in the first chemical oxide film formed in the first step. That is, the first chemical oxide film having a low atomic density including the pores serves as a catalyst, and the oxidation reaction for forming the second chemical oxide film proceeds sequentially. Thereby, an even higher quality chemical oxide film can be formed.

  In the first step and the second step, two kinds of oxidizing solutions of low concentration (preferably less than azeotropic concentration) and high concentration (preferably azeotropic concentration or more) or a gas thereof are prepared, The first and second chemical oxide films may be formed, or the high concentration is sequentially switched in multiple steps (preparing two or more kinds of oxidizing solutions or gases thereof) from the low concentration to the high concentration. Also good. It is also possible to increase the concentration continuously from a low concentration to a high concentration. That is, by concentrating a low-concentration solution, a high-concentration solution can be continuously obtained. For example, if an oxidizing solution having an azeotropic concentration is heated to an azeotropic concentration, by maintaining the heating state, the oxidizing solution having an azeotropic concentration has a constant solution composition / vapor composition. Become. Thereby, the growth of the chemical oxide film can be controlled by time management. Therefore, the formation (thickness and quality) of the chemical oxide film can be controlled with higher accuracy.

  In this forming method, it is preferable to perform a nitriding step of nitriding the chemical oxide film after the oxide film forming step. As a result, the chemical oxide film is nitrided, and a nitrided chemical oxide film composed of the chemical oxide film and the nitride film is formed.

  The nitride chemical oxide film basically has an intermediate property between the oxide film and the nitride film depending on its composition. For example, since the diffusion coefficient of impurities is smaller in the nitride film than in the oxide film (thermal nitridation), the nitrided chemical oxide film diffuses impurities doped in the gate electrode, especially boron, into the Si substrate. Excellent ability to prevent Therefore, the nitrided chemical oxide film can be applied to a semiconductor device that requires an extremely thin gate insulating film (for example, 4 nm or less).

  Thus, the nitriding process is one means for improving the performance of the transistor, and the film quality of the chemical oxide film can be further improved by the nitriding process. Therefore, it is possible to reduce the thickness of the chemical oxide film.

  Note that “nitriding the chemical oxide film” means nitriding at least a part of the formed chemical oxide film. In other words, nitriding is a process in which a chemical oxide film is formed by oxidation of the semiconductor surface, and then heated in an atmosphere containing nitriding species to form a part of the chemical oxide film or a chemical oxidation film formed on the semiconductor surface. This is a process of nitriding the interface between the film and its semiconductor.

Examples of the nitriding treatment include ammonia (NH ₃ ) nitridation, nitrous acid (N ₂ O) nitridation, and nitric oxide (NO) nitridation. In these methods, the nitriding species is ammonia, nitrous acid, or nitric oxide. Note that the nitrided chemical oxide film obtained by NO nitriding does not deteriorate the characteristics, and is excellent in the dielectric breakdown resistance and hot carrier resistance of the gate insulating film over time.

  The method for manufacturing a semiconductor device of the present invention (this manufacturing method) includes an oxide film forming step of forming a chemical oxide film by any of the oxide film forming methods described above.

  In this manufacturing method, after forming a chemical oxide film on the surface of the semiconductor or after nitriding the chemical oxide film, an oxide film, a silicon nitride film, a dielectric film (for example, a high dielectric film / ferroelectric film) It is preferable to have a step of forming at least one film of the body membrane.

  According to another aspect of the present invention, there is provided a semiconductor device obtained by any one of the above semiconductor device manufacturing methods, comprising a chemical oxide film obtained by oxidizing the semiconductor with the oxidizing solution. .

  According to another aspect of the present invention, there is provided a semiconductor device manufacturing apparatus comprising: an oxide film forming unit that forms a chemical oxide film on a semiconductor surface in a state where a voltage is applied to the semiconductor; And a function of forming a chemical oxide film on a semiconductor surface (function of growing a chemical oxide film on a semiconductor surface) by any of the above-described oxide film forming method or any of the semiconductor device manufacturing methods described above. It is a feature.

  According to each of the above-described configurations and methods, a high-quality chemical oxide film having a desired thickness can be uniformly formed on the semiconductor surface at a low temperature and a low voltage, as in the present forming method. That is, the quality of the chemical oxide film can be improved, and a high-quality chemical oxide film with a low leakage current density can be formed. Therefore, for example, even if a chemical oxide film is used as the insulating film, the chemical oxide film functions as a high-quality insulating film, and therefore can be made thinner (for example, several nm or less) than the current insulating film. Therefore, a high-performance semiconductor device having a high-quality chemical oxide film can be provided.

  Further, in order to solve the above problems, the method for surface oxidation of a SiC substrate of the present invention applies a voltage in a nitric acid solution to keep the SiC substrate at a positive potential and forms a silicon dioxide film on the surface of the SiC substrate. It is characterized by that.

  Moreover, in order to solve the above-described problem, the method for manufacturing a SiCMOS type semiconductor device of the present invention includes a step of forming a silicon dioxide film on the surface of the SiC substrate by applying a voltage to the SiC substrate in a nitric acid solution. It is characterized by that.

  According to another aspect of the present invention, there is provided a SiCMOS type semiconductor device comprising a silicon dioxide film formed on a SiC substrate by the SiC substrate oxidation method or the SiC-MOS type semiconductor device manufacturing method. .

  The SiC-MOS type integrated circuit of the present invention is characterized by using the SiC-MOS type semiconductor device.

  Further, the SiC-MOS type semiconductor device and the SiC-MOS type integrated circuit manufacturing apparatus of the present invention can be obtained by oxidizing the SiC substrate or the SiC-MOS type semiconductor device by the silicon dioxide film on the SiC substrate. It is characterized by having an oxide film forming part for forming the film.

  According to each of the above-described configurations and methods, it is possible to provide a technique for forming a silicon dioxide film having a good interface state at a low temperature and in a short time on the surface of the SiC substrate and a method for using the same.

  As described above, the method for forming an oxide film according to the present invention includes the oxide film forming step of forming the chemical oxide film on the semiconductor surface by causing the oxidizing solution or the gas to act on the semiconductor. Therefore, a high-quality chemical oxide film having a desired thickness can be uniformly formed on the semiconductor surface at a low temperature and a low voltage. That is, it is possible to improve the quality of the chemical oxide film and to form a high-quality chemical oxide film having a low leakage current density.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to FIGS. In the following, a manufacturing method of a MOS capacitor in which a silicon dioxide film and an electrode are formed on a silicon substrate will be described as an example. Note that the present invention is not limited to this.

  In the manufacturing method of the MOS capacitor (semiconductor device) in the present embodiment, the chemical oxide film is formed on the semiconductor surface by applying an oxidizing solution or a gas to the semiconductor in a state where a voltage is applied to the semiconductor. It has an oxide film forming step. Hereinafter, the oxide film forming process characteristic of the present invention will be described mainly.

  FIG. 1 is a schematic sectional view of a main part of a manufacturing apparatus (semiconductor device manufacturing apparatus) used in a method for forming a silicon dioxide film (chemical oxide film) on a silicon substrate as a first embodiment of the present invention. Yes, a silicon substrate 1 to be processed is immersed in an oxidizing solution (oxidizing solution or gas thereof) 3 in a processing tank 2, and a power source 4 is connected to the silicon substrate 1 to treat the silicon substrate 1 and the processing. A predetermined voltage can be applied between the counter electrode 5 installed in the tank 2. In other words, this manufacturing apparatus has an oxide film forming unit for performing the oxide film forming method of the present invention described below.

  In the manufacturing apparatus of FIG. 1, when a voltage is applied to the silicon substrate 1 and the counter electrode 5, the oxidizing solution 3 in the treatment tank 2 undergoes electrolysis to oxidize the silicon substrate 1 from the oxidizing solution 3. Is formed. The oxidized species oxidizes the silicon substrate 1 to form a silicon dioxide film on the surface of the silicon substrate 1.

  2A to 2F disclose a method of manufacturing a MOS capacitor by forming a silicon dioxide film (chemical oxide film) and an electrode on a silicon substrate 11 by the manufacturing apparatus shown in FIG. It is process flow sectional drawing, The method of one Embodiment of this invention is demonstrated below.

  First, as shown in FIG. 2A, an isolation region 12 is formed on a silicon substrate 11 in advance. Here, a P-type substrate having a specific resistance of 10 to 15 Ωcm and a plane orientation (100) is used as the silicon substrate 11, and after boron (B) of a channel stopper is implanted into this silicon substrate 11, On the surface, a silicon dioxide film made of LOCOS (local oxidation of silicon) technology as an isolation region 12 was formed with a thickness of about 500 nm. This isolation region 12 is not limited to LOCOS, but may be, for example, one in which a silicon dioxide film embedded in a silicon substrate is formed. In this process, when the natural oxide film 13 is formed on the surface of the silicon substrate 11, after the well-known RCA cleaning method, that is, cleaning with an ammonia-hydrogen peroxide aqueous solution, the concentration is 0.5% (vol.%). ), The natural oxide film 13 can be completely removed as shown in FIG. 2B.

  Next, after rinsing (cleaning) with ultrapure water for 5 minutes, the silicon substrate 11 is immersed in a solution (oxidizing solution) having a high oxidizing power even at a low concentration, which is filled in the processing tank 2 shown in FIG. In addition, a positive voltage of 10 V is applied to the silicon substrate 11 between the counter electrode 5 installed in the processing tank 2 through the power source 4 and maintained at room temperature for about 10 minutes. Here, a nitric acid aqueous solution having a nitric acid concentration of 1 mol (mol./l) is used as the oxidizing solution, and the carbon dioxide having a thickness of about 10 nm is formed on the active region 14 on the surface of the silicon substrate 11 as shown in FIG. A silicon film 15 was formed uniformly.

The conditions for applying voltage to the silicon substrate 11 at this time are selected in consideration of the temperature when the heating temperature is set to 200 ° C. or lower. As an example, the number of positive potentials on the side of the silicon substrate 11 between the electrode arrangement such that a uniform electric field is applied to the entire surface of the silicon substrate 11, for example, between the silicon substrate and a counter electrode arranged in parallel therewith. In the case of the nitric acid aqueous solution having a nitric acid concentration of 1 mol (mol./l), it is preferable to set it appropriately in the range of 5 to 20 V DC. By applying this voltage, anions or radicals such as O ⁻ and OH ⁻ of oxidizing species are drawn into the surface of the silicon substrate 11 and pass through the silicon dioxide film 15 even if it is formed. The oxidation reaction at the surface is uniformly accelerated. As a result, a silicon dioxide film 15 is generated on the surface of the silicon substrate 11.

  In addition, the conditions of the voltage application to the silicon substrate 11 can suppress the pulling of oxidized species to the surface of the silicon substrate 11 by applying a negative potential thereto. Even when no voltage is applied to the silicon substrate 11 (that is, when the applied voltage value is zero), the silicon dioxide film 15 grows on the surface of the silicon substrate 11 due to the oxidization species that has arrived on the surface of the silicon substrate 11 due to diffusion. Therefore, in order to stop the growth of the chemical oxide film on the surface of the silicon substrate 11, an appropriate negative voltage is preferably applied. This can be made to function effectively when it is carried out when the growth of the silicon dioxide film 15 on the surface of the silicon substrate 11 is finished and the silicon substrate 11 is taken out (separated) from the oxidizing solution 3 in the processing bath 2.

  Subsequently, as shown in FIG. 2D, a metal film (a film containing metal) 16 was formed on the silicon dioxide film 15 and the isolation region 12. The metal film 16 was formed by depositing an aluminum alloy containing 1 wt% silicon to a thickness of about 200 nm by a known resistance heating vapor deposition method (hereinafter, this type of metal film electrode is simply referred to as an aluminum electrode). . Instead of the metal film 16, a polysilicon electrode (material) can be attached and used.

  Thereafter, the metal film 16 is patterned into a desired shape, and the electrode 17 is formed as shown in FIG. 2F, whereby a MOS capacitor can be manufactured.

  Next, the characteristics of the MOS capacitor thus manufactured will be described.

  FIG. 3 is a so-called CV characteristic diagram showing the relationship between the capacitance (C) and the applied voltage (V) of the MOS capacitor obtained in this embodiment. As can be seen from this characteristic diagram, when a positive voltage is applied to the electrode 17, an inversion layer is induced at the interface with the oxide film (semiconductor surface), and a stable capacitor capacity (capacitance) is obtained. .

  Further, as can be seen from the CV characteristic diagram of FIG. 3, the above-described MOS capacitor also has a leakage current density of a MOS capacitor formed by using a silicon dioxide film formed by a normal high temperature thermal oxidation method as an insulating film. It is the same as or higher than the leakage current density characteristic, and high performance is confirmed with certainty.

  In the above description, an example in which a nitric acid aqueous solution having a nitric acid concentration of 1 mol is used as the oxidizing solution or oxidizing gas is used. Instead of this, nitric acid, perchloric acid, sulfuric acid, ozone dissolved at any concentration Water, hydrogen peroxide solution, mixed solution of hydrochloric acid and hydrogen peroxide solution, mixed solution of sulfuric acid and hydrogen peroxide solution, mixed solution of ammonia water and hydrogen peroxide solution, mixed solution of sulfuric acid and nitric acid, Wang It is also possible to use at least one solution selected from the group of water and further oxidative boiling water, its gas, or a mixture thereof. That is, these oxidizing solutions or oxidizing gases may be used alone or in a mixture. These oxidizing solutions or oxidizing gases generate oxidizing species having strong oxidizing power, such as oxygen ions and radicals such as oxygen ions, hydroxide ions, and peroxide ions. For this reason, by using the silicon substrate 11 on which the silicon dioxide film 15 is to be formed as an anode, even after the silicon dioxide film 15 is formed, these oxidized species are converted into the surface of the silicon substrate 11 (the interface between the silicon substrate 11 and the silicon dioxide film 15). ).

  In the case where an aqueous nitric acid solution is used as the oxidizing solution, the oxidizing power against silicon is strong even when the nitric acid concentration is a low concentration in the range of 1 to 65% (weight ratio, hereinafter referred to as wt). Even without an applied voltage, it is suitable for forming the silicon dioxide film 15 described above.

  In addition, an oxidizing solution having a high concentration, particularly a nitric acid solution having a nitric acid concentration exceeding 65% (wt), for example, a nitric acid aqueous solution having a nitric acid concentration of 68% (wt) or more (azeotropic concentration or more) has an oxidizing power against silicon. It is extremely strong, and a uniform silicon dioxide film 15 is formed even without a voltage applied to the silicon substrate 11. In this nitric acid aqueous solution, when the heating temperature is maintained at 120.7 ° C. (above the so-called azeotropic temperature), nitric acid and water become azeotropic, and the concentration of the solution and vapor (ie, gas) is constant. Thus, the growth of the silicon dioxide film 15 can be controlled by time management.

  Since they have a strong oxidizing power even with a vapor, that is, an oxidizing gas, even if this vapor is applied to the silicon substrate 11 without applying a voltage, a silicon dioxide film (chemical oxide film) 15 is formed on the surface of the silicon substrate 11. Can be formed. In this case, the temperature of the silicon substrate 11 can be selected as appropriate. However, the generation rate of the silicon dioxide film 15 can be increased by applying a voltage to the silicon substrate 11 to form the silicon dioxide film 15.

  Further, among the above oxidizing solutions or gases thereof, a high concentration oxidizing solution or oxidizing gas is an azeotropic nitric acid, sulfuric acid and water, which is an azeotropic mixture of nitric acid and water used in the present embodiment. When it is at least one selected from the group of azeotropic sulfuric acid which is an azeotropic mixture and azeotropic perchloric acid which is an azeotropic mixture of perchloric acid and water, the oxidizing power is particularly strong, and according to the present invention It is particularly suitable for an oxide formation method. In these azeotropes, even if the applied voltage to the silicon substrate 11 is low (even if the applied voltage is zero), the oxide film forming step and the performance of the resulting silicon dioxide film 15 are both stable.

  Thus, in this embodiment, the oxidizing solution or gas thereof is preferably an azeotropic mixture having an azeotropic concentration or more, more preferably an azeotropic mixture with water, and azeotropy with water. It consists of at least one solution selected from the group of azeotropic nitric acid that is a mixture, azeotropic sulfuric acid that is an azeotrope with water, and azeotropic perchloric acid that is an azeotrope with water, or a gas thereof. Further preferred. Furthermore, these azeotropes are particularly preferably caused to cause the oxidizing solution or gas thereof heated to the azeotropic temperature or higher to act on the semiconductor.

  In the above description, the silicon dioxide film 15 is formed using a nitric acid aqueous solution of one kind of concentration in the oxide film forming step, but an oxidizing solution such as nitric acid having a plurality of different concentrations or its gas is applied. Is also possible. However, in this case, the oxidizing solution or the gas thereof is an azeotropic mixture.

  That is, a first silicon dioxide film (first chemical oxide film) is formed on the surface of the silicon substrate 11 by allowing an oxidizing solution having a lower azeotropic concentration or its gas to act on the silicon substrate (semiconductor). A second silicon dioxide film (second chemical oxidation) that is thicker than the first silicon dioxide film by causing an oxidizing solution or gas thereof having an azeotropic concentration or higher to act on the first silicon dioxide film in one step. A second step of forming a film), and at least one of the first step and the second step is performed by performing the oxidation in the state of applying the voltage to the silicon substrate (that is, applying a voltage to the silicon substrate). A first chemical oxide film or a second chemical oxide film may be formed on the surface of the silicon substrate by applying a reactive solution or a gas thereof to the silicon substrate. That is, at least one of the first step and the second step can be performed by the oxide film forming step.

  As a result, similarly to the oxide film forming step described above, a high-quality chemical oxide film having a desired thickness can be uniformly formed on the silicon substrate surface at a low temperature and a low voltage. That is, the film quality of the silicon dioxide film can be improved, and a high-quality silicon dioxide film with a low leakage current density can be formed. Therefore, for example, even if a silicon dioxide film is used as an insulating film, the silicon dioxide film functions as a high-quality insulating film, so that it can be made thinner (for example, several nm or less) than the current insulating film.

  Furthermore, in particular, the first silicon dioxide film is applied to the second silicon dioxide film because an oxidizing solution having a concentration lower than the azeotropic concentration in the first step and an oxidizing solution having a concentration higher than the azeotropic concentration or the gas in the second step are allowed to act. Compared to a chemical oxide film having a lower atomic density. That is, in the first step, a first silicon dioxide film having a hole (pore) can be formed. In the second step, the second silicon dioxide film is formed by the action of the oxidizing solution or its gas on the pores present in the first silicon dioxide film formed in the first step. That is, the first silicon dioxide film having a low atomic density including pores serves as a catalyst, and the oxidation reaction of the second silicon dioxide film proceeds sequentially. Thereby, an even higher quality silicon dioxide film can be formed.

  In the first step and the second step, two kinds of oxidizing solutions of low concentration (preferably less than azeotropic concentration) and high concentration (preferably azeotropic concentration or more) or a gas thereof are prepared, The first and second silicon dioxide films may be formed, and the low concentration is gradually changed to the high concentration in multiple steps (preparing two or more kinds of oxidizing solutions or gases thereof). Also good. It is also possible to increase the concentration continuously from a low concentration to a high concentration. For example, if an oxidizing solution having an azeotropic concentration is heated to an azeotropic concentration, the oxidizing solution has a constant solution composition / vapor composition by maintaining the heating state. Thereby, the growth of the chemical oxide film can be controlled by time management. Therefore, the formation (thickness and quality) of the silicon dioxide film can be controlled with higher accuracy.

In the present embodiment, voltage application to the silicon substrate 11 thereby contributes to increasing the film thickness while increasing the generation rate of the silicon dioxide film 15 on the silicon substrate 11. By applying a voltage to the silicon substrate 11, anions or radicals such as O ⁻ and OH ⁻ which are oxidizing species in the solution are attracted, and the silicon dioxide film 15 is formed in the silicon dioxide film 15 even after the silicon dioxide film 15 is formed. Passing through and reaching the surface of the silicon substrate 11 is facilitated, the oxidation reaction rate is increased, and a thick silicon dioxide film 15 can be obtained.

In the present embodiment, it is preferable to perform a nitriding step for nitriding the silicon dioxide film 15 described above. For example, as the nitriding step, a silicon nitride-containing silicon dioxide film (nitrided chemical oxide film) in which a part of the surface of the silicon dioxide film 15 is converted into silicon nitride in a gas containing nitrogen, particularly by plasma nitriding, is formed. Alternatively, a thick insulating film (oxide film) such as SiO ₂ can be formed on the silicon nitride-containing film after the nitriding treatment by a CVD method or the like. Thereby, the silicon dioxide film 15 becomes a film of silicon nitride and silicon dioxide (nitrided chemical oxide film). By performing such nitriding treatment, the dielectric breakdown characteristics and charge trapping characteristics of the chemical oxide film can be improved.

In the present embodiment, a high dielectric film, for example, a composite film in which hafnium oxide, aluminum oxide, or the like is laminated on the silicon dioxide (SiO ₂ ) film 15 described above is used as a gate insulating film of a MOS transistor. Can do. In that case, performance improvement of transistor characteristics (improvement of mobility due to reduction of leakage current, reduction of interface state, etc.) can be obtained as compared with the case where only a high dielectric film is used. The silicon dioxide film 15 formed under the high dielectric film (on the silicon substrate 11 side) may be an extremely thin film of 1 nm or less, for example, and may be formed without applying a voltage. Note that the silicon dioxide film 15 formed by the usual thermal oxidation method is about 1 nm, and the film quality is low. Therefore, the leakage current and the interface state are large and cannot be practically used.

On the other hand, since the silicon dioxide (SiO ₂ ) film 15 of this embodiment is of high quality, it is suitable for a composite film having a laminated structure in which a thick insulating film is formed on the silicon dioxide film 15. That is, it is suitable for a gate insulating film of a MOS transistor. Further, not only the high dielectric film but also the silicon dioxide film 15 of the present embodiment can be similarly applied to a film formed by laminating ferroelectric films.

  Further, in the present embodiment, the example in which the MOS capacitor is manufactured using the single crystal silicon substrate 11 as the substrate to be processed for forming the silicon dioxide film 15 has been described. The present invention can also be applied to the case where a thin film transistor (TFT) is formed by forming polycrystalline (including microcrystalline) silicon or amorphous silicon on a substrate such as PET.

  Furthermore, in this embodiment, since the uniform silicon dioxide film 15 is obtained, the single crystal silicon substrate 11 is not limited to a planar shape, and is a substrate having a three-dimensional shape, a spherical unevenness, or a curved surface. It is also possible to use a curved surface area for a transistor channel. That is, according to the above method, a high-quality insulating film such as the formed silicon dioxide film 15 can be uniformly formed at a low temperature in accordance with the unevenness and curved surface of the silicon substrate 11.

  Furthermore, the above-described steps are not limited to the case where a MOS capacitor is manufactured as a semiconductor device. That is, in this embodiment, the MOS capacitor has been described as an example. However, when a gate insulating film of a thin film transistor (TFT) is formed, a silicon nitride-containing film is interposed between the laminated silicon dioxide film or the laminated silicon dioxide film. As a result, a high-performance insulating film with few interface states can be obtained, and a high-performance TFT can be obtained. Also, as a large-scale integrated circuit (LSI), charge coupled device (CCD), etc., as an interlayer insulating film of a multilayer wiring structure formed by using a polycrystalline silicon electrode material or the like as a wiring, or as a capacitor insulating film of a memory such as a flash memory It can be used and expected to be used in this field.

  In this embodiment, the example in which the MOS capacitor is manufactured using the silicon substrate 11 of single crystal silicon as the substrate to be processed has been described. However, each step described here is performed when the single crystal silicon substrate is used. Not limited to this, it is fully applicable when thin film transistors (TFTs) are formed of polycrystalline silicon (including microcrystals), amorphous silicon, silicon carbide, silicon / germanium, etc. on a glass substrate or a substrate such as PET. it can.

  In the present embodiment, a DC voltage is applied to the silicon substrate 11, but an AC voltage may be applied. When an AC voltage is applied, a silicon dioxide film can be formed by controlling the pulse in the same manner as in the case of a DC voltage. Further, the film thickness of the silicon dioxide film to be formed can be controlled by controlling the pulse.

  In the above description, aluminum is used as the metal film 16 (metal-containing film). However, as the film containing metal atoms, aluminum, magnesium, nickel, chromium, platinum, palladium, tungsten, titanium, and tantalum are used. Examples include a film containing a metal atom selected from the group. The film containing metal atoms is preferably a film containing active metal atoms, for example, a metal film such as aluminum, magnesium, or nickel, or an alloy film such as aluminum containing silicon. As the film containing metal atoms, a compound such as titanium nitride or tantalum pentoxide can be used.

  The oxide film forming method of the present invention and the conventional anodic oxidation method have the following differences.

  Conventionally, an anodic oxidation method has been performed as a method of forming an oxide film on a semiconductor surface in a state where a voltage is applied to the semiconductor. The anodic oxidation method is a method in which an oxide film is formed on a semiconductor surface by accelerating the movement of ions of a semiconductor component in an electrolyte that does not dissolve the oxide film.

For example, when a SiO ₂ film is formed on a Si substrate by an anodic oxidation method, Si ⁺ ions are guided from the surface of the Si substrate to the SiO ₂ film by applying a voltage to the Si substrate. Then, the Si ⁺ ions released from the Si substrate permeate through the formed SiO ₂ film and move to guide the released Si ⁺ ions to the surface of the SiO ₂ film. Then, by the oxidation of Si ⁺ ions in the SiO ₂ film surface to form a SiO ₂ film on the SiO ₂ film surface. That is, in the anodic oxidation, the growth of the SiO ₂ film occurs at the SiO ₂ film surface. That is, in the anodic oxidation, by directing the Si ⁺ ions in the SiO ₂ film surface of SiO ₂ film surface, the oxidation reaction takes place.

On the other hand, in the method for forming an oxide of the present invention (the present forming method), an oxidizing solution having a strong oxidizing power or a gas thereof (a highly oxidizing solution or a gas thereof) is used, for example, SiO _{2 on} a Si substrate. When forming a film, by applying a voltage to the Si substrate, active species (oxidized species) such as dissociated oxygen ions (O ⁻ ) and oxygen atoms are generated on the surface of the Si substrate. This active species moves to the SiO ₂ / Si substrate interface, and reacts with the Si substrate at this interface to form a SiO ₂ film. As described above, in the present forming method, by applying a voltage to the Si substrate, oxidizing species such as O ⁻ ions and oxygen atoms are introduced to the surface of the Si substrate (interface between the Si substrate and the SiO ₂ film). Therefore, after the formation of the SiO ₂ film, the ions or radicals of the oxidizing species oxidize Si on the surface of the Si substrate (the interface between the Si substrate and the SiO ₂ film), thereby forming the SiO ₂ film. In other words, the growth of the SiO ₂ film is not a SiO ₂ film surface, it occurs in the Si substrate surface (interface between the Si substrate and the SiO ₂ film). That is, in this formation method, oxidation ions or radicals are guided to the surface of the Si substrate (interface between the Si substrate and the SiO ₂ film) to oxidize on the surface of the Si substrate (interface between the Si substrate and the SiO ₂ film). A reaction takes place.

  Thus, in this formation method, an oxidation reaction occurs on the semiconductor surface (interface between the semiconductor and the chemical oxide film), whereas in the anodic oxidation method, an oxidation reaction occurs on the oxide film surface. Therefore, the growth site of the chemical oxide film differs between the present formation method and the anodic oxidation method. That is, in anodic oxidation, an oxide film is formed on the side opposite to the substrate from the interface, whereas in this formation method, a chemical oxide film is formed on the substrate side from the interface. That is, the interface between the Si substrate and the silicon dioxide film moves to the silicon bulk side with the oxidation reaction and is always clean. Therefore, in this forming method, good interface characteristics can be obtained.

  Furthermore, in the anodic oxidation method, it is necessary to release the semiconductor component ions to be oxidized from the semiconductor surface and to guide the semiconductor component ions to the oxide film surface, so that a high voltage is required. On the other hand, in this formation method, since the chemical oxide film grows on the semiconductor surface (interface between the semiconductor and the chemical oxide film), it is not necessary to release semiconductor component ions to be oxidized from the semiconductor surface. Therefore, in this forming method, it is possible to form a chemical oxide film at a lower voltage than in the anodic oxidation method.

In Patent Document 1, in order to form an oxide film on the surface of a silicon substrate at a low voltage, an oxide film is formed after a porous oxide film is formed. That is, in Patent Document 1, it is essential to form a porous oxide film. Further, the quality of the formed oxide film is insufficient.
On the other hand, in this formation method, a chemical oxide film can be formed on the semiconductor surface without forming such a porous oxide film.

  In the conventional anodic oxidation, a porous silicon substrate is used in order to perform an oxidation reaction at a low voltage.

  On the other hand, in the present forming method, since an oxidizing solution having a strong oxidizing power or a vapor thereof is used, it is not always necessary to use a porous processing substrate (for example, a porous silicon substrate).

  Also, the present invention can be expressed as [1] to [19] below. That is, [1] In the oxide film forming method of the present invention, a chemical oxide film is formed on the surface of the semiconductor by applying an oxidizing solution or its gas while applying a predetermined voltage of less than 100 V to the semiconductor. It is characterized by forming.

  [2] A method for forming an oxide film according to the present invention is the method for forming an oxide film according to [1], wherein the semiconductor is selected from single crystal silicon, polycrystalline silicon, amorphous silicon, silicon carbide, and silicon-germanium. The chemical oxide film is mainly composed of a silicon oxide film.

  [3] The oxide film formation method of the present invention is the oxide film formation method according to [1] or [2], wherein the oxidizing solution or gas thereof is nitric acid, perchloric acid, sulfuric acid, ozone-dissolved water. , Hydrogen peroxide solution, mixed solution of hydrochloric acid and hydrogen peroxide solution, mixed solution of sulfuric acid and hydrogen peroxide solution, mixed solution of ammonia water and hydrogen peroxide solution, mixed solution of sulfuric acid and nitric acid, aqua regia And at least one solution selected from the group of boiling water or a gas thereof.

  [4] The method for forming an oxide film according to the present invention is the method for forming an oxide film according to the above [1] or [2], wherein the oxidizing solution or the gas thereof is an azeotropic mixture with water. And at least one solution selected from the group consisting of azeotropic sulfuric acid which is an azeotrope with water and azeotropic perchloric acid which is an azeotrope with water, or a gas thereof.

  [5] The method for forming an oxide film according to the present invention is the method for forming an oxide film according to any one of [1] to [4], wherein after the chemical oxide film is formed on the surface of the semiconductor, The method includes a step of nitriding the chemical oxide film.

  [6] The method for forming an oxide film of the present invention comprises a step of forming a first chemical oxide film on the semiconductor surface by causing a low concentration oxidizing solution or gas to act on the surface of the semiconductor, and a high concentration oxidation. And a step of forming a second chemical oxide film exceeding the thickness of the first chemical oxide film by the action of a reactive solution or a gas thereof.

  [7] The method for forming an oxide film according to the present invention includes the step of forming the first chemical oxide film and the step of forming the second chemical oxide film in the method for forming an oxide film according to [6]. A voltage is applied to the semiconductor in at least one of the steps.

  [8] The method for forming an oxide film according to the present invention is the method for forming an oxide film according to [6] or [7], wherein the low-concentration oxidizing solution or a gas thereof is an aqueous nitric acid solution, an aqueous sulfuric acid solution, or an excess solution. The solution is selected from a solution having a concentration lower than the azeotropic concentration or a gas thereof in at least one of the chloric acid aqueous solution groups, and the high-concentration oxidizing solution or the gas has an azeotropic concentration in at least one of the aqueous solution groups. It is selected from a solution or a gas thereof.

  [9] In the method of manufacturing a semiconductor device according to the present invention, an oxidizing solution or a gas thereof is allowed to act on a substrate including a semiconductor while a predetermined voltage is applied to the semiconductor to thereby generate ions or radicals of oxidizing species. A step of forming a desired chemical oxide film by reacting on the surface of the semiconductor is provided.

  [10] A method for manufacturing a semiconductor device according to the present invention is the method for manufacturing a semiconductor device according to [9], wherein the oxidizing solution or the gas thereof is nitric acid, perchloric acid, sulfuric acid, ozone-dissolved water, peroxidation. Hydrogen water, mixed solution of hydrochloric acid and hydrogen peroxide solution, mixed solution of sulfuric acid and hydrogen peroxide solution, mixed solution of ammonia water and hydrogen peroxide solution, mixed solution of sulfuric acid and nitric acid, aqua regia and boiling water It consists of at least 1 solution chosen from the group of these, or its gas.

  [11] A method of manufacturing a semiconductor device according to the present invention includes a step of forming a first chemical oxide film on a surface of a semiconductor by causing a low concentration oxidizing solution or gas to act on the surface of the semiconductor, and a high concentration oxidation. And a step of forming a second chemical oxide film exceeding the thickness of the first chemical oxide film by the action of a functional solution or a gas thereof.

  [12] A method of manufacturing a semiconductor device according to the present invention includes the step of forming the first chemical oxide film and the step of forming the second chemical oxide film in the method of manufacturing a semiconductor device according to [11]. A voltage is applied to the semiconductor in at least one of the steps.

  [13] A method for manufacturing a semiconductor device according to the present invention is the method for manufacturing a semiconductor device according to [11] or [12], wherein the low-concentration oxidizing solution or gas thereof is nitric acid, perchloric acid, sulfuric acid. Selected from the group of a mixture of at least one selected from water and water, and selected in a concentration range lower than the azeotropic concentration, the high-concentration oxidizing solution or the gas thereof is selected from the group and the low concentration A high concentration exceeding the set value of the concentration range is selected.

  [14] A method for manufacturing a semiconductor device according to the present invention is the method for manufacturing a semiconductor device according to any one of [11] to [13], wherein the high-concentration oxidizing solution or oxidizing gas is water. At least one solution selected from the group consisting of azeotropic nitric acid as an azeotrope with water, azeotropic sulfuric acid as an azeotrope with water, and azeotropic perchloric acid as an azeotrope with water, or a gas thereof It is characterized by comprising.

  [15] A method for manufacturing a semiconductor device according to the present invention is the method for manufacturing a semiconductor device according to any one of [9] to [14], wherein the semiconductor is monocrystalline silicon, polycrystalline silicon, or amorphous. It is characterized by comprising at least one selected from silicon, silicon carbide and silicon-germanium.

  [16] A method for manufacturing a semiconductor device according to the present invention is the method for manufacturing a semiconductor device according to any one of [9] to [15], wherein a chemical oxide film is formed on the surface of the semiconductor, The method includes a step of nitriding the chemical oxide film.

  [17] A method for manufacturing a semiconductor device according to the present invention is the method for manufacturing a semiconductor device according to any one of [9] to [16], wherein a chemical oxide film is formed on the surface of the semiconductor, or It is characterized by comprising a step of forming at least one film of chemical vapor deposition (CVD) oxide film, silicon nitride film, high dielectric film, and ferroelectric film after nitriding the chemical oxide film .

  [18] The semiconductor device manufacturing apparatus of the present invention has a function of forming a first chemical oxide film on the semiconductor surface by causing a low concentration oxidizing solution or gas to act on the surface of the semiconductor, and a high concentration oxidation. It has a function of forming a second chemical oxide film exceeding the thickness of the first chemical oxide film by the action of a reactive solution or its gas.

  [19] The semiconductor device manufacturing apparatus of the present invention has a function of forming a chemical oxide film on the surface of the semiconductor by applying an oxidizing solution or its gas to a substrate including the semiconductor while applying a voltage. It is characterized by.

  According to the method for forming an oxide film of the present invention, an oxidizing solution or a gas thereof is allowed to act on a semiconductor while applying a predetermined voltage lower than 100 V, which is lower than that in the case of anodic oxidation, to generate ions of oxidizing species. Alternatively, when a desired chemical oxide film is formed by reacting radicals on the surface of the semiconductor, the applied voltage is appropriately selected to uniformly control the high-quality chemical oxide film at a low temperature with a predetermined thick film. can do.

  In addition, according to the method for forming an oxide film of the present invention, a step of forming a first chemical oxide film on the semiconductor surface by causing a low concentration oxidizing solution or gas to act on the surface of the semiconductor, and a high concentration By providing a step of forming a second chemical oxide film that exceeds the thickness of the first chemical oxide film by the action of an oxidizing solution or its gas, a high-quality chemical oxide film having a desired thickness can be formed at a low temperature. It can be formed into a film.

  According to the method for manufacturing a semiconductor device of the present invention, an oxidizing solution or a gas thereof is allowed to act on a substrate including a semiconductor while a predetermined voltage lower than 100 V, which is lower than that in the case of anodization, is applied to the semiconductor. Then, by providing a step of forming a desired chemical oxide film by reacting ions or radicals of oxidizing species on the surface of the semiconductor, the chemical oxide film is selected as a predetermined thick film to manufacture a semiconductor device. be able to.

  According to the method of manufacturing a semiconductor device of the present invention, a step of forming a first chemical oxide film on the semiconductor surface by causing a low concentration oxidizing solution or gas to act on the semiconductor surface and a high concentration oxidizing property. By providing a step of forming a second chemical oxide film exceeding the thickness of the first chemical oxide film by acting a solution or a gas thereof, a predetermined thick film including the first chemical oxide film is obtained. A semiconductor device can be manufactured.

  According to the semiconductor device manufacturing apparatus of the present invention, a function of forming a first chemical oxide film on the semiconductor surface by causing a low concentration oxidizing solution or gas to act on the semiconductor surface and a high concentration oxidizing property. The first chemical oxide film is formed on the substrate including the semiconductor by providing a function of forming a second chemical oxide film exceeding the thickness of the first chemical oxide film by acting a solution or a gas thereof. A semiconductor device having high performance and stable characteristics can be manufactured by forming an insulating film having a predetermined thick film.

  According to the semiconductor device manufacturing apparatus of the present invention, by providing a function of forming a chemical oxide film on the surface of the semiconductor by allowing an oxidizing solution or a gas thereof to act on a substrate including the semiconductor while applying a voltage. By forming the chemical oxide film in a predetermined thick film, a semiconductor device having high performance and stable characteristics can be manufactured.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  Hereinafter, the present embodiment will be described in detail by way of examples, but the present invention is not limited to the following examples.

[Example 1]
Next, an example (Example) in which the silicon dioxide film 15 is formed on the silicon substrate 11 using nitric acid as the oxidizing solution will be described.

A well-known RCA cleaning method for an n-type silicon wafer having a specific resistance of about 10 Ωcm and a plane orientation (100) (the entire oxide film including the isolation film (isolation region (LOCOS oxide film)) formed on the silicon substrate 11) Then, an ohmic contact electrode is provided on a part of the wafer surface, and the wafer is immersed in a 1 mol (mol./l) nitric acid (HNO ₃ ) aqueous solution at room temperature (25 ° C.). A voltage was applied from the variable power source 4 in the range of 5 to 20 V between the counter electrode 5 and the platinum reference electrode to form a silicon dioxide (SiO ₂ ) film 15 on the wafer surface.

FIG. 4 is a growth film thickness-time characteristic diagram of the SiO ₂ film 15 showing the relationship between the processing time (minutes) and the film thickness (nm) of the SiO ₂ film 15 using the applied voltage as a parameter. When the applied voltage is 5 V, the film thickness of the SiO ₂ film increases in a parabolic manner with respect to the processing time. From this, the growth of the SiO ₂ film 15 is caused by O ⁻ or OH which is an oxidizing species. ^- by anion or radical, such as, is deemed to have become diffusion limited. When the applied voltage is 10 V, the thickness of the SiO ₂ film 15 increases linearly with respect to the processing time, and it is recognized that the reaction rate is controlled. That is, when the applied voltage is high, the movement of anions or radicals such as O ⁻ and OH ⁻ that are oxidation species to the SiO ₂ / Si interface (the interface between the silicon dioxide film 15 and the silicon substrate 11) is promoted. The oxidation reaction at the interface seems to be the rate-limiting process. However, in any case, the growth of the SiO ₂ film 15 is a chemical oxide film by an oxidation reaction at the SiO ₂ / Si interface.

According to this embodiment, when the applied voltage to the silicon substrate 11 is set to 10 V, the relationship between the thickness of the SiO ₂ film 15 and the time is almost linear, so the time is increased and the film thickness is 20 to 30 nm. It is sufficiently possible to form the SiO ₂ film 15.

FIG. 5 shows a case where an aluminum electrode (metal film 16) having a diameter of 0.3 mm is formed on the SiO ₂ film 15 to form the Al / SiO ₂ / Si (100) structure MOS diode (capacitor) with the applied voltage of 5 V, 60 minutes current by MOS diodes in the case of the SiO ₂ film obtained in (treatment time) - a voltage (I-V) characteristic diagram. The thickness of the SiO ₂ film 15 at this time was about 6.1 nm as measured by the capacitance-voltage (CV) method assuming that the relative dielectric constant of the SiO ₂ film 15 was 3.9. Moreover, the leakage current densities when 4V and −4V voltages are applied to the aluminum electrode on the SiO ₂ film 15 are 8 × 10 ⁻⁸ A / cm ² and 9 × 10 ⁻⁹ A / cm ^{2, respectively.} Although the SiO ₂ film 15 was formed at room temperature, it was a relatively low value.

FIG. 6 shows the leakage current density and the SiO _{2 in} the MOS diode when the electric field strength in the SiO ₂ film is set to 5 MV / cm for the SiO ₂ films formed at the applied voltages of 5 V, 10 V, 15 V and 20 V, respectively. It is the correlation diagram which plotted the relationship with a film thickness at random. The leak current density was 1 × 10 ⁻⁷ A / cm ² or less in all observed film thickness ranges.

FIG. 7 shows an IV characteristic diagram of a MOS diode having a SiO ₂ film 15 formed by applying a voltage of 10 V to a silicon substrate 11 in a 0.01 mol perchloric acid (HClO ₄ ) aqueous solution for 10 minutes, and C— It is a V characteristic diagram. The leakage current densities when 3V and −3V voltages are applied to the aluminum electrode on the SiO ₂ film 15 are 7 × 10 ⁻⁸ A / cm ² and 8 × 10 ⁻⁹ to 8 × 10 ^{−8, respectively.} A / cm ² , and there is approximately 0.9 V hysteresis in the CV characteristics. The SiO ₂ film thicknesses determined from X-ray photoelectron spectrum (XPS) measurement and CV characteristics were 8.5 nm (XPS) and 6.7 nm (CV).

The above is the result when the post-treatment such as annealing is not performed on the SiO ₂ film 15 formed in the HNO ₃ aqueous solution or the HClO ₄ aqueous solution. After the SiO ₂ film 15 was formed, this was subjected to heat treatment in nitrogen (post-oxidation annealing—hereinafter referred to as POA treatment), whereby the electrical characteristics were improved as shown below.

FIGS. 8 and 9 show the SiO ₂ film 15 (shown in FIG. 7) formed by applying a voltage of 10 V to the silicon substrate 11 for 10 minutes in the above-mentioned 0.01 mol perchloric acid (HClO ₄ ) aqueous solution. FIG. 4 is an IV characteristic diagram and a CV characteristic diagram obtained as a MOS structure by forming an aluminum electrode after POA treatment by heating at 200 ° C. for 30 minutes in nitrogen. According to this, the leak current densities when 4 V and −4 V are applied to the aluminum electrode on the SiO ₂ film 15 are 1 to 8 × 10 ⁻⁸ A / cm ² and 1 to 8 × 10 respectively. ^{It was −9} A / cm ² , and this heat treatment (POA treatment) decreased to about 1/5 to 1/10 of the value before the treatment. Also, in the CV characteristics, the hysteresis was about 0.4 V, and this heat treatment (POA treatment) was about half.

Further, from the Fourier infrared absorption (FT-IR) spectrum, desorption of water molecules in the SiO ₂ film 15 was observed by the heat treatment at 200 ° C. From this, the improvement in the electrical characteristics described above was due to the trap level. This is probably due to the desorption of water molecules.

The thickness of the SiO ₂ film obtained from XPS measurement is 8.5 nm, which is the same as that before the heat treatment, but the thickness of the SiO ₂ film obtained from CV characteristics is 7.6 nm, which is a slightly increased value before the heat treatment. . This seems to be due to the decrease in dielectric constant due to the separation of water molecules by the heat treatment. That is, when the relative dielectric constant of the SiO ₂ film 15 obtained from the CV characteristics and the XPS measurement is compared before and after the heat treatment, it is estimated to be 4.9 (before treatment) and 4.4 (after treatment). It is considered that the relative dielectric constant is high due to the presence of H ₂ O (water molecules) and OH ions having a large polarity in the film, and H ₂ O is desorbed after the treatment to reduce the relative dielectric constant.

10 and 11 show that a SiO ₂ film 15 formed at an applied voltage of 20 V in a 1 mol nitric acid (HNO ₃ ) aqueous solution is heated at 600 ° C. in nitrogen, and then a MOS diode is formed thereon. It is the obtained CV characteristic diagram and IV characteristic diagram. According to this, the hysteresis in the CV characteristic is considerably reduced, and the leakage current density at the applied voltage of 10 V and −10 V to the electrode is about 1 × 10 ⁻⁵ A / cm ^{2 in the} IV characteristic. And about 1 × 10 ⁻⁶ A / cm ² . H ₂ O in the SiO ₂ film 15 is removed by heat treatment at 200 ° C. in nitrogen, but OH ions are not removed unless the temperature is 500 ° C. Therefore, the improvement of the electrical characteristics by the heat treatment at 600 ° C. is due to the removal of the OH group.

  On the other hand, since it was confirmed that OH ions were removed by POA treatment at 200 ° C. in a hydrogen atmosphere or heat treatment after forming the metal film 16 (post-metallization annealing—hereinafter referred to as PMA treatment), It was found that carrying out at 200 ° C. in an atmosphere is effective for removing water molecules and OH groups.

[Embodiment 2]
FIG. 12 is a schematic configuration diagram of a semiconductor device manufacturing apparatus used in the second embodiment. That is, it is a schematic configuration diagram of a main part of an oxide film forming unit that implements a method of forming a silicon dioxide film on a SiC substrate.

As the SiC substrate 111 for the substrate to be processed, a 3C-SiC (100) epitaxial substrate was used. In this SiC substrate, an epitaxial layer (doping concentration: 1.25E + 17 cm ⁻³ ) having a thickness of 6 μm is formed on a crystal plate having a resistivity of 0.016 Ω-cm (doping concentration: 4.50E + 18 cm ⁻³ ). It is. Note that a 3C-SiC substrate is used here, but a 4H-SiC substrate, a 6H-SiC substrate, and the like are also applicable.

  In the apparatus of FIG. 12, first, the SiC substrate 111 is immersed in a 1 mol / L nitric acid aqueous solution 3 in the treatment tank 2, and the power source 4 is connected to the SiC substrate. Then, a predetermined voltage is applied between the SiC substrate 111 and the platinum counter electrode 5 installed in the processing bath 2 to form the silicon dioxide film 6 on the surface of the SiC substrate 111. The applied voltage at this time is a constant voltage set by the three-electrode reference electrode 7 installed in the treatment tank 2.

  The surface of SiC substrate 111 is preferably subjected to a cleaning process by an RCA cleaning method as a pre-process.

  In the nitric acid aqueous solution 3, the SiC substrate 111 was made positive from the power source 4, the counter electrode 5 was made negative, and a voltage of 30 V (+30 V) set by the reference electrode 7 was applied to the SiC substrate 111 for 10 minutes. As a result, a silicon dioxide film 6 having a uniform film thickness was formed on the surface of the SiC substrate 111. The voltage application was performed by a constant potential method that maintains a constant voltage while monitoring the potential of the reference electrode 7.

  The voltage applied at the time of film formation is practically set to the voltage set by the reference electrode 7 in the range of 2 to 50V, preferably 5 to 30V. Within this range, the reaction rate can be easily controlled, and the film quality can also be controlled.

  As the nitric acid aqueous solution 3, one having a concentration of 0.01 mol / L or more can be used.

  FIG. 14 is a view showing an SEM image showing a cross section of the silicon dioxide film 6 formed on the surface of the SiC substrate 111. According to this figure, it was confirmed that a thick silicon dioxide film 6 of about 1 μm was obtained.

  The applied voltage, the concentration of the nitric acid aqueous solution 3, and the treatment time are not particularly limited, and can be appropriately changed according to the target film thickness. These conditions can be set in the same manner as in the first embodiment, for example.

  FIG. 13 is a cross-sectional view of a SiC-MOS type integrated circuit manufactured by using this silicon dioxide film forming method. In this SiC-MOS type integrated circuit, a separation layer 12 is formed on a SiC substrate 111, and a gate oxide film 15, a gate electrode 17, a source electrode 18, and a drain electrode 19 are formed. Here, both the isolation layer 12 and the gate oxide film 15 are silicon dioxide films, and can be formed by the above-described method. Note that the impurity layers of the source electrode 18 and the drain electrode 19 may be formed using low-concentration impurities in order to improve the breakdown voltage. A p-type impurity layer may be formed under the separation layer 12. Further, the isolation layer 12 may be formed by forming a trench in the SiC substrate and forming an oxide film in the trench.

  That is, the power supply 4 is connected to the SiC substrate in a state where the SiC substrate 111 to be processed is immersed in the 1 mol / L nitric acid aqueous solution 3 in the processing tank 2. By applying a constant voltage set by the three-electrode system reference electrode 7 between the SiC substrate 111 and the platinum counter electrode 5 installed in the processing tank 2, for example, a film thickness of 10 nm is applied to the surface of the SiC substrate 111. The silicon dioxide film for the gate oxide film 15 and the isolation layer 12 for element isolation having a film thickness of 1 μm were formed. Thereby, silicon dioxide film 6 can be formed on the surface of SiC substrate 111 by a low temperature process. Accordingly, it is possible to realize a SiC-MOS type semiconductor device and a SiC-MOS type integrated circuit using the same by forming a silicon dioxide film having a good interface state at a low temperature in a short time on the surface of the SiC substrate. . A predetermined annealing process (nitriding process) may be performed on the formed silicon dioxide film. Thereby, the interface state of the silicon dioxide film can be further increased.

  The SiC-MOS integrated circuit of FIG. 13 constitutes a lateral MOSFET (metal-oxide semiconductor field-effect transistor), but constitutes a vertical power SiC-MOSFET for a power device as shown in FIG. You can also

  FIG. 15 is a cross-sectional view of a vertical SiC-MOSFET manufactured by using the silicon dioxide film forming method described above. In the vertical SiC-MOSFET of FIG. 15, the drain electrode 19 is formed on one surface of the SiC substrate 111, and the gate oxide film 15 and the source electrode 18 are formed on the other surface with a space therebetween. A gate electrode 17 is formed on the gate oxide film 15. The vertical SiC-MOSFET of FIG. 15 can also be manufactured in the same manner as the SiC-MOS integrated circuit of FIG. Again, as in FIG. 13, the gate oxide film 15 is a silicon dioxide film formed by applying a voltage to the SiC substrate 111.

  As described above, according to the present invention, it is possible to provide a surface oxidation method for a SiC substrate in which a voltage is applied to the SiC substrate in a nitric acid solution to maintain a positive potential and a silicon dioxide film is formed on the surface of the substrate. This method can also be used for the manufacture of semiconductor devices. That is, it can be applied as a method for manufacturing a semiconductor device including a step of applying a voltage to a SiC substrate in a nitric acid solution to form a silicon dioxide film on the surface of the SiC substrate.

  Semiconductor devices to which this method can be applied include, for example, SiC power MOSFETs, MOSICs, ICs, LSIs, and the like, which are used for these gate oxide films, gate insulating films, element isolation layers, and substrate surface protection layers Can do.

  Thus, the present embodiment is characterized in that a voltage is applied to the SiC substrate in a nitric acid solution to maintain a positive potential, and a silicon dioxide film is formed on the substrate surface. In addition, the present embodiment includes a step of applying a voltage to a SiC substrate in a nitric acid solution to form a silicon dioxide film on the surface of the substrate.

  Although not shown, it was confirmed that a silicon dioxide film having a very good interface was formed on the surface of the SiC substrate using TEM analysis. That is, according to this embodiment, it is possible to easily form a silicon dioxide film having a good interface state on the surface of the SiC substrate.

  Thus, according to the present invention, a SiC substrate is measured in a nitric acid solution at a constant voltage, for example, a reference electrode of a three-electrode electrochemical cell, and a voltage of 2 to 50 V is applied to maintain a positive potential. A silicon dioxide film having an arbitrary thickness from a thin film to a thick film can be easily formed on the surface of the SiC substrate at a low temperature (for example, room temperature) in a short time. For example, a silicon dioxide film having a thickness of about several nm to 1 μm can be formed.

  Therefore, by controlling the applied voltage and time, it becomes possible to form the gate oxide film (for example, 10 to 20 nm) and the separation layer (for example, 500 nm to 1 μm) of the SiC-MOS type transistor (SiCMOS type semiconductor device). . Furthermore, it is possible to configure a SiC-MOS type integrated circuit including the SiC-MOS type transistor. In this case, since the interface state between the gate oxide film and the separation layer can be greatly reduced, the performance of the lateral SiC-MOS transistor can be greatly improved, and a SiC-MOS integrated circuit with good high frequency characteristics can be realized. In the conventional method, since a silicon dioxide film having a sufficient thickness cannot be formed on the surface of the SiC substrate, a SiC integrated circuit cannot be realized.

  Furthermore, even if it is used for a gate oxide film of a vertical power SiC-MOS, naturally the interface state of the gate oxide film can be greatly reduced, so that its switching characteristics and the like can be greatly improved.

  According to the present invention, a silicon dioxide film having a predetermined thickness can be formed at room temperature in a short time, including a step of forming a silicon dioxide film on the surface of the substrate by applying a voltage in a nitric acid solution to the SiC substrate. .

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  According to the present invention, a high-quality chemical oxide film can be formed to a desired thickness at a low voltage and low temperature, and a semiconductor device having such a chemical oxide film can be manufactured. Can be used. The present invention also provides, for example, a vertical SiC-MOSFET gate oxide film for power devices, a lateral SiC-MOSFET isolation layer (isolation oxide film) for high-frequency devices, and a gate oxide film of an SiC-MOS integrated circuit. And can be used for semiconductor devices such as an isolation oxide film for element isolation. Further, the present invention can be applied to various functional devices that use a silicon dioxide film formed on the surface of SiC, for example, a capacitive oxide film for SiC memory.

It is a schematic sectional drawing which shows the principal part structure of the manufacturing apparatus used for formation of the silicon dioxide film on the silicon substrate which concerns on one Embodiment of this invention. 2A to 2F are cross-sectional views showing the steps of a method for forming a silicon dioxide film on a silicon substrate according to an embodiment of the present invention. It is a graph which shows the relationship between the capacity | capacitance (C) and the voltage (V) in the MOS capacitor obtained by the method of FIG. 6 is a graph showing the relationship between the growth film thickness and time in the silicon dioxide film of Example 1. 3 is a graph showing the relationship between current and voltage in the MOS diode of Example 1. 3 is a graph showing the correlation between the leakage current density and the SiO 2 film thickness in the MOS diode of Example 1. It is a graph which shows the relationship between the electric current in the MOS diode of Example 1, and the relationship between a capacity | capacitance and a voltage. It is a graph which shows the relationship between the electric current at the time of forming an electrode after heat-processing the MOS structure of FIG. 7 at 200 degreeC. It is a graph which shows the relationship between the capacity | capacitance and voltage in the MOS structure of FIG. It is a graph which shows the relationship between a capacity | capacitance at the time of forming an electrode after heat-processing the MOS structure of FIG. 7 at 600 degreeC. 11 is a graph showing the relationship between current and voltage in the MOS structure of FIG. 10. FIG. 5 is a schematic configuration diagram of a semiconductor device manufacturing apparatus used in a second embodiment. It is sectional drawing of the lateral MOSFET in Embodiment 2 of this invention. It is a figure which shows the SEM image of the cross section of the silicon dioxide film formed in the surface of the SiC substrate in Embodiment 2 of this invention. It is sectional drawing of the vertical MOSFET in Embodiment 2 of this invention.

Explanation of symbols

1, 11, silicon substrate (semiconductor)
3 solution (oxidizing solution)
15 Silicon dioxide film (chemical oxide film)
111 SiC substrate (semiconductor)

Claims (19)

In a method for forming an oxide film having an oxide film forming step of forming a chemical oxide film on a semiconductor surface in a state where a voltage is applied to the semiconductor,
The oxide film forming step is characterized in that the chemical oxide film is formed on the semiconductor surface by allowing an oxidizing solution or a gas thereof to act on the semiconductor.   The method for forming an oxide film according to claim 1, wherein the oxide film forming step is performed by immersing a semiconductor to which the voltage is applied in an oxidizing solution. The semiconductor contains silicon,
3. The method of forming an oxide film according to claim 1, wherein the chemical oxide film is a silicon oxide film. The semiconductor is at least one selected from single crystal silicon, polycrystalline silicon, amorphous silicon, silicon carbide, and silicon germanium,
4. The method of forming an oxide film according to claim 3, wherein the chemical oxide film is a silicon oxide film.   The oxidizing solution or gas thereof is nitric acid, perchloric acid, sulfuric acid, ozone-dissolved water, hydrogen peroxide solution, a mixed solution of hydrochloric acid and hydrogen peroxide solution, a mixed solution of sulfuric acid and hydrogen peroxide solution, ammonia water And at least one solution selected from the group consisting of a mixed solution of water and hydrogen peroxide, a mixed solution of sulfuric acid and nitric acid, aqua regia, and boiling water, a gas thereof, or a mixture thereof. Item 5. The method for forming an oxide film according to any one of Items 1 to 4.   6. The method for forming an oxide film according to claim 1, wherein the oxidizing solution or the gas thereof is an azeotropic mixture.   The oxidizing solution or its gas is from the group of azeotropic nitric acid that is an azeotrope with water, azeotropic sulfuric acid that is an azeotrope with water, and azeotropic perchloric acid that is an azeotrope with water. 7. The method for forming an oxide film according to claim 6, comprising at least one selected solution or a gas thereof.   8. The method for forming an oxide film according to claim 6, wherein the oxidizing solution heated to an azeotropic temperature or a gas thereof is allowed to act on a semiconductor. A first step of forming a first chemical oxide film on the semiconductor surface by allowing an oxidizing solution having a concentration lower than the azeotropic concentration or a gas thereof to act on the semiconductor;
A second step of forming a second chemical oxide film thicker than the first chemical oxide film by allowing an oxidizing solution or gas thereof having an azeotropic concentration or higher to act on the first chemical oxide film; A method of forming an oxide film comprising:
The chemical oxide film is formed on the semiconductor surface by causing the oxidizing solution or the gas to act on the semiconductor in a state in which a voltage is applied to the semiconductor in at least one of the first step and the second step. And forming an oxide film.   The method for forming an oxide film according to any one of claims 1 to 9, wherein a nitriding step of nitriding the chemical oxide film is performed after the oxide film forming step.   A method for manufacturing a semiconductor device, comprising: an oxide film forming step of forming a chemical oxide film by the oxide film forming method according to claim 1.   Further, after a chemical oxide film is formed on the surface of the semiconductor or after the chemical oxide film is nitrided, an oxide film, a silicon nitride film, a high dielectric film, and a ferroelectric film are formed on the chemical oxide film. The method for manufacturing a semiconductor device according to claim 11, further comprising a step of forming at least one film. A semiconductor device obtained by the method for manufacturing a semiconductor device according to claim 11 or 12,
A semiconductor device comprising a chemical oxide film in which a semiconductor is oxidized by the oxidizing solution. In a semiconductor device manufacturing apparatus having an oxide film forming portion for forming a chemical oxide film on a semiconductor surface in a state where a voltage is applied to the semiconductor,
The oxide film forming portion forms a chemical oxide film on a semiconductor surface by the oxide film forming method according to any one of claims 1 to 10 or the semiconductor device manufacturing method according to claim 11 or 12. A manufacturing apparatus of a semiconductor device having a function.   A method of oxidizing a SiC substrate, wherein a voltage is applied to the SiC substrate in a nitric acid solution to maintain a positive potential, and a silicon dioxide film is formed on the surface of the SiC substrate.   A method of manufacturing a SiC-MOS type semiconductor device, comprising: applying a voltage to a SiC substrate in a nitric acid solution to form a silicon dioxide film on the surface of the SiC substrate.   A SiC-MOS type semiconductor device comprising a silicon dioxide film formed on a SiC substrate by the oxidation method according to claim 15 or the SiC-MOS type semiconductor device manufacturing method according to claim 16.   A SiC-MOS type integrated circuit using the SiC-MOS type semiconductor device according to claim 17.   An oxide film forming portion for forming a silicon dioxide film on the SiC substrate is provided by the SiC substrate oxidation method according to claim 15 or the SiC-MOS type semiconductor device manufacturing method according to claim 16. An SiC-MOS type semiconductor device and an SiC-MOS type integrated circuit manufacturing apparatus are characterized.