WO2008018304A1

WO2008018304A1 - Method for forming insulating film, apparatus for forming insulating film, method for manufacturing semiconductor device, semiconductor device and surface treatment method for silicon carbide substrate

Info

Publication number: WO2008018304A1
Application number: PCT/JP2007/064759
Authority: WO
Inventors: Hikaru Kobayashi
Original assignee: Hikaru Kobayashi
Priority date: 2006-08-08
Filing date: 2007-07-27
Publication date: 2008-02-14
Also published as: JP5224570B2; JP2008066317A

Abstract

An insulating film applicable to a semiconductor device using silicon carbide (SiC) or the like is formed by a chemical oxidation method at a low temperature. After heating at least the surface of a base (10) in a hydrogen-containing atmosphere, the surface is immersed into an oxidizing solution (22), or the solution (22) is sprayed over the surface, or the surface is exposed to a vapor of the solution (22). Consequently, reactivity of the surface of the substrate (10), which is in contact with the oxidizing solution (22), is improved, and an insulating film which exhibits high performance even when formed thin is formed on the surface of the substrate (10).

Description

Specification

Insulating film forming method, insulating film forming apparatus, semiconductor device manufacturing method, semiconductor device and silicon carbide substrate surface treatment method

Technical field

The present invention relates to a method for forming an insulating film on a surface of a base material, specifically, selected from the group of silicon carbide, silicon, and polysilicon, a method for forming the insulating film on the surface of the base material, a semiconductor including the insulating film The present invention relates to a method of manufacturing a device, a semiconductor device thereof, and a surface treatment method of a substrate of silicon carbide.

Background art

In semiconductor devices, particularly MOS-structured semiconductor devices (diodes and transistors), it is important to improve the performance of insulating films used for miniaturization of circuit elements due to higher integration and higher density. For example, in the case of a semiconductor device configured using a silicon substrate, particularly a MOS transistor or a MOS capacitor, a so-called high temperature thermal oxidation method is used to form an insulating film such as a gate insulating film or a capacitive insulating film. It is done. In this method, a silicon substrate is heated in an oxidizing gas such as dry oxygen (dry) or water vapor (wet) at a high temperature of 800 ° C. or higher, so that a silicon dioxide (SiO 2) film is formed on the surface of the silicon substrate. Shape

2

Made. However, in this case, since the initial growth rate of the silicon dioxide film is fast, it is extremely difficult to control the film thickness during this period.For example, a high-performance ultrathin S film with a thickness of several nanometers (nm) or less is formed with good control. There are considerable difficulties. In addition, the high temperature thermal oxidation method uses

2

When dopants diffuse in the con substrate and a thick film is formed by long-time heat treatment, consideration must be given to shallow changes and fluctuations and destruction of the junction.

[0003] On the other hand, when the substrate is silicon carbide (SiC), a high temperature thermal oxidation method in wet or dry oxidizing gas at 1100 ° C to 1200 ° C is adopted when forming the gate insulating film of the MOS transistor Then, a silicon dioxide film having a thickness of several tens of nanometers (nm) is formed. However, the film quality itself of the silicon dioxide film, which takes a long time to form, is also more efficient than the SiO film formed by high-temperature thermal oxidation of silicon (Si). Bad

2

It is enough. In addition, high-temperature processing requires increased equipment costs and other processes. Limitation of design freedom on process or materials used will greatly hinder industrialization. As a result, many challenges remain in improving the performance and industrialization of so-called MOS devices, particularly when the substrate is silicon carbide.

[0004] Further, when the substrate is silicon carbide, in addition to the above-mentioned problems, there is a problem that deep irregularities exist on the surface of the substrate, and because the carbon remains in the formed insulating film, the fixed charge density and the interface There is a problem that the level density is high. Therefore, technical barriers for industrial use of a film formed by high-temperature thermal oxidation as a gate insulating film for a semiconductor device having a MOS structure on silicon carbide are very high. Realization of is strongly demanded.

As an insulating film forming method other than the high temperature thermal oxidation method, for example, several hundreds. Chemical vapor deposition of SiO film on the silicon substrate surface by thermally decomposing monosilane etc. under C condition

2

Phase growth (CVD), deposition of SiO film in plasma (PCVD), or sputtering

2

There are various physical vapor deposition (PVD) methods, such as knockers and vapor deposition. However, these vapor deposition methods also do not sufficiently satisfy the requirements for MOS transistor gate insulating films.

On the other hand, the present inventor has already contacted an oxidizing solution or a gas thereof with a semiconductor substrate containing silicon to form a SiO film on the surface of the semiconductor substrate.

2

Has developed a practical oxidation technology (see, for example, Patent Document 1).

[0007] In general, as an insulating film applied to a semiconductor device, a silicon dioxide film formed on a silicon substrate by a high temperature thermal oxidation method is stable in performance, which is desirable in terms of the characteristics of the semiconductor device. However, from the viewpoint of the stability of various shapes on the semiconductor surface and the maintenance of the process, the industry expectation for the formation of an insulating film under low temperature conditions, such as the above-mentioned chemical oxidation technology Is very big.

Patent Document 1: Japanese Patent Application Laid-Open No. 2005-311302 (Publication date: November 4, 2005)

Patent Document 2: Japanese Patent Laid-Open No. 2005-311303 (Publication date: November 4, 2005)

Patent Document 3: Japanese Patent Laid-Open No. 2005-311352 (Publication date: November 4, 2005)

Patent Document 4: Japanese Patent Laid-Open No. 2002-289612 (Opened: October 4, 2002)

Non-Patent Document 1: Nagayama, 2 others, "Chemical method of Si02 / S purchase at low temperature and spectroscopy Observations ”, Abstracts of the Physical Society of Japan, The Physical Society of Japan, 15 August 2003, Vol. 58, No. 2, p. 771

Disclosure of the invention

Problems to be solved by the invention

[0008] Although the object of the present invention is not particularly limited to the following points, for example, one object is a cubic silicon carbide (3C-SiC, hereinafter simply referred to as SiC or silicon carbide). For example, a high-performance oxide film is formed at low temperature using a chemical method on a substrate with large surface irregularities or a high interface state density such as is there. Specifically, an insulating film forming method for chemically forming an insulating film on the surface of a substrate using an oxidizing solution, a mist solution, or a gas thereof, an apparatus for forming the insulating film, or an insulating film for the insulating film. A semiconductor device including a film and a method for manufacturing the semiconductor device are provided.

[0009] Another object of the present invention is to form a silicon dioxide film as a chemical oxide film developed as an oxidation method at a low temperature even on a substrate selected from silicon carbide, silicon, and polysilicon. An object of the present invention is to provide a method for forming an insulating film on a substrate surface that can be stably and reliably performed, a device for forming the insulating film, a semiconductor device including the insulating film, and a method for manufacturing the semiconductor device. .

[0010] Further, another object of the present invention is to oxidize a substrate such as a silicon carbide substrate, which has poor substrate surface flatness and high interface state density, by the above-described chemical method. To provide a surface treatment method as a pretreatment for effective film formation.

Means for solving the problem

[0011] If the present invention is carried out, it has been considered difficult until now to improve the flatness of the substrate surface at the atomic layer level after the formation of the insulating film, or to reduce the fixed charge and interface state density. As a result, an ultrathin high-performance insulating film can be formed.

[0012] The present invention does not impose any strict limitation on the target substrate, but is particularly applicable to MOS transistors using silicon carbide or the like that are strongly demanded by the industry. If the formation of a thin insulating film is realized by a low-temperature process, the semiconductor industry will It can be said that it greatly contributes to the exhibition. The inventor has conducted earnest research to further improve the performance of an insulating film obtained by a method of forming an insulating film using a chemical method and a semiconductor device using the insulating film. As a result of the research, the inventor has found that an unprecedented high-performance insulating film can be formed on the surface of a substrate by adopting a new processing method and manufacturing method that change the conventional idea. The inventor has also found that a semiconductor device having excellent electrical characteristics can be obtained by the insulating film.

That is, in the method for forming an insulating film on one substrate surface of the present invention, at least the substrate surface is heated in an atmosphere containing hydrogen, and then the substrate surface is immersed in an oxidizing solution. Or spraying the solution onto the substrate surface, or exposing the substrate surface to the vapor of the solution.

[0014] With this, a high-performance insulating film that can also be applied to a semiconductor device can be obtained by improving the flatness of the substrate surface or reducing the interface state density as described above.

[0015] In addition, a method of manufacturing a semiconductor device according to the present invention includes a step of forming an insulating film by any one of the methods described above.

[0016] By using this manufacturing method, a semiconductor device having excellent electrical characteristics can be manufactured even if the surface of the base material is physically rough or a base material (for example, a semiconductor substrate) having a high interface state density. I can do it.

[0017] Further, one semiconductor device according to the present invention includes an insulating film formed by any one of the methods described above.

[0018] If this insulating film is formed, the flatness of the substrate surface is improved or the interface state density is reduced, so even if the initial flatness of the substrate surface is poor or A semiconductor device with excellent electrical characteristics can be obtained even with a high interface state density! / And a base material (for example, a semiconductor substrate).

[0019] Also, one insulating film forming apparatus of the present invention includes a means for heating at least the surface of the base material in an atmosphere containing hydrogen, and then immersing the base material surface in an oxidizing solution, or Means are provided for spraying the solution onto the substrate surface or exposing the substrate surface to the vapor of the solution.

[0020] Thereby, the flatness of the substrate surface is improved, or the reduction of the interface state density is achieved. Therefore, for example, when a semiconductor device having a MOS structure is subsequently manufactured, the semiconductor device has excellent electrical characteristics.

In addition, the surface treatment method for a silicon carbide substrate of the present invention includes a step of heating at 200 ° C. to 500 ° C. in an atmosphere containing hydrogen.

[0022] Thereby, introduction of hydrogen into the silicon carbide surface layer is promoted. Further, the hydrogen once taken into the silicon carbide surface layer is released only to the extent that the effects of the present invention are not impaired by the heat treatment. As a result, when an insulating film is subsequently formed by a chemical oxidation method, the speed of forming the insulating film on the silicon carbide surface is improved. Further, if a MOS structure is manufactured thereafter, for example, a semiconductor device with very little leakage current can be obtained.

The invention's effect

[0023] According to the present invention, the flatness of the substrate surface at the atomic layer level after the formation of the insulating film is improved, or the interface state density of the substrate surface layer is reduced, and a high-performance insulating film is achieved. Can form force S. Further, by manufacturing a semiconductor device using the insulating film obtained by the present invention, a semiconductor device having excellent electrical characteristics can be obtained. In addition, when the present invention is applied to a silicon carbide substrate, an insulating film is subsequently formed by a chemical oxidation method, so that the speed of forming an insulating film on the surface of silicon carbide is about 1.6 compared with the conventional case. Will be doubled. Furthermore, if a MOS structure is subsequently manufactured, the leakage current is sufficiently reduced to such an extent that it can be practically used as a MOS transistor, so that a high-performance semiconductor device can be obtained.

Brief Description of Drawings

FIG. 1A shows a heat treatment apparatus in a hydrogen-containing atmosphere among the insulating film forming apparatuses according to one embodiment of the present invention.

FIG. 1B is an immersion treatment apparatus using an oxidizing solution among the insulating film forming apparatuses according to one embodiment of the present invention.

[FIG. 1C] Among the insulating film forming apparatuses according to another embodiment of the present invention, an exposure apparatus using vapor of an oxidizing solution.

FIG. 1D shows an oxidizing solution vapor in an insulating film forming apparatus according to another embodiment of the present invention. Or a fog exposure device.

FIG. 2A is a cross-sectional view illustrating the structure of a structure manufactured according to one embodiment of the present invention.

FIG. 2B is a cross-sectional view illustrating a configuration of a semiconductor device (MOS capacitor) manufactured in another embodiment of the present invention.

FIG. 3 is a TEM analysis cross-sectional view of an insulating film formed in one embodiment of the present invention.

[FIG. 4A] X-ray photoelectron spectrum of insulating film formed in one embodiment of the present invention (

It is a characteristic view by XPS) measurement.

FIG. 4B is a characteristic diagram of the insulating film formed in one embodiment of the present invention and a comparative insulating film by X-ray photoelectron spectrum (XPS) measurement with respect to Si2p.

FIG. 5 is a CV characteristic 1 drawing of a semiconductor device (MOS capacitor) manufactured in another embodiment of the present invention.

FIG. 6 is an IV characteristic diagram of a semiconductor device (MOS capacitor) manufactured in another embodiment of the present invention.

FIG. 7 is an IV characteristic diagram relating to voltage dependency of a leakage current value of a semiconductor device (MOS capacitor) manufactured in another embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In this description, common parts are denoted by common reference symbols throughout the drawings.

1A and 1B are explanatory views of the insulating film forming apparatus of the present embodiment. In this embodiment, 3C—SiC (cubic silicon carbide) is used as the base material (hereinafter referred to as a substrate or a silicon carbide substrate for convenience). In addition, this silicon carbide substrate is an n-type with a surface orientation of (100) and a surface resistivity of 0.02-0.03 Ω'cm, with an epitaxially grown layer of 6 m thickness formed on the substrate. It was a substrate.

First, using the processing apparatus 100 as shown in FIG. 1A, the substrate 10 is processed for 20 minutes in a processing chamber in a hydrogen atmosphere heated to 400 ° C. Specifically, while the processing chamber 14 is heated by the heater 16, the hydrogen bombing force also causes hydrogen to flow into the processing chamber 1. By introducing into the substrate 14, the substrate 10 supported by the support 12 in the processing chamber 14 is heated. The treatment condition in the chamber at this time was 100% hydrogen at normal pressure.

[0027] Here, the hydrogen concentration is preferably 75 vol% or more, and more preferably 80 vol% or more. For example, the operation based on the present invention can be achieved in a processing time of about 10 to 60 minutes by appropriately selecting a processing temperature in a gas atmosphere having a hydrogen concentration of 80 vol% or more at normal pressure in the processing chamber 14. Is done. In this case, an inert gas such as nitrogen shown in FIG. 1A can be included as a gas other than hydrogen. In addition, even if it is less than 50 vol%, the effect of the present invention will not be completely lost. The higher the hydrogen concentration, the better. However, if hydrogen is used in a certain range of concentrations, there is a danger of explosion and its handling is very difficult. Therefore, the concentration used may be limited to avoid such dangers.

[0028] The heating temperature is preferably 200 ° C or higher and 500 ° C or lower! /. Even if the temperature is outside the above temperature range, if the force is less than 200 ° C where the effect of the present invention is not expected to be completely lost, hydrogen may not be sufficiently supplied to the substrate surface layer. This is because if the temperature exceeds 600 ° C., the hydrogen once taken into the substrate surface layer is likely to be released due to the high temperature. From these viewpoints, a more preferable heating temperature range is 250 ° C. or higher and 550 ° C. or lower, and most preferable is 250 ° C. or higher and 500 ° C. or lower.

[0029] Table 1 shows the result of comparing the surface roughness of the substrate with and without the heat treatment in the hydrogen atmosphere described above. This surface roughness was measured using an AFM (Atomic Force Microscope).

Yes

[0030] [Table 1]

[0031] As shown in Table 1, by performing the processing of the present embodiment, the mean square roughness (Root In Mean Square, about 60% of the substrate surface roughness before processing was reduced. In spite of the low temperature treatment method as in this embodiment, a silicon carbide substrate having an extremely smooth surface at the atomic layer level with a root mean square roughness of 0.5 nm or less on the substrate surface could be obtained.

Next, using the processing apparatus 200 as shown in FIG. 1B, the substrate subjected to the above-described processing is immersed in an oxidizable solution. Specifically, the substrate 10 held by a known substrate holder (not shown) for convenience is concentrated nitric acid (aqueous solution) having a concentration of 4 Owt% at room temperature (about 25 ° C) filled in the treatment tank 24. Soaked in. In this state, the substrate 10 is heated to a state where the concentrated nitric acid (aqueous solution) 22 is in a boiling state by a heater 26 (for example, an acid-resistant quartz heater for liquid heating). If this state continues, it will eventually lead to azeotropic nitric acid (azeotropic nitric acid) with a boiling point of 120.7 ° C and a nitric acid concentration of 68 wt%. As a result, the nitric acid concentration and boiling point are maintained even if heating continues. As a result of maintaining this state for about 7 hours, as shown in FIG. 2A, a structure 500 including a film 51 having a uniform thickness was formed on the substrate 10.

[0033] Here, the initial concentration of concentrated nitric acid (aqueous solution) is not particularly limited, and even if the concentration is other than 40 wt% (for example, 20 wt%, 60 wt%, or 70 wt%), The effect is played. Further, the temperature of the solution in the immersion treatment in the oxidizing solution (here, concentrated nitric acid) may not reach the boiling state completely. That is, since the nitric acid concentration gradually approaches the azeotropic concentration by heating the oxidizing solution, it is not always necessary to heat to the boiling point. The effect of the present invention is also substantially achieved by the vicinity of the boiling point (for example, a temperature about 1 to 5 ° C. lower than the boiling point).

[0034] Further, instead of a solution with a continuous increase in concentration as in this embodiment, at least one predetermined concentration (for example, 40 wt%) heated near or at the boiling point is used as a solution for substrate immersion. , 60 wt% concentrated nitric acid (aqueous solution) and approximately azeotropic or azeotropic nitric acid solution may be prepared in advance, in which case the same effect as in this embodiment Here, near the boiling point is a temperature about 1 to 5 ° C lower than the boiling point, and the substantially azeotropic state is about a temperature lower than the azeotropic state; Temperature.

[0035] In the case where a film is formed in multiple stages by preparing two or more kinds of the aforementioned solutions, the initial stage In the treatment of the floor (if it is a two-stage treatment, the treatment in the first stage), it is not always necessary to heat the oxidizing solution from the beginning to near the boiling point or to the boiling point! /. For example, as a first step, the substrate 10 after the heat treatment in the atmosphere containing hydrogen described above is heated in the state of being immersed in concentrated nitric acid (aqueous solution) having a concentration of 40 wt% at room temperature to be close to the boiling point. Increases the boiling point to form a very thin film having a thickness of 0.1 nm to 1 nm. Thereafter, as a second step, a method of continuously forming a film to a desired thickness by immersing the substrate 10 in nitric acid or azeotropic nitric acid in a higher concentration and substantially azeotropic state may be used. Even in such a case, an effect similar to the effect of the present invention is exhibited. On the other hand, the concentration of concentrated nitric acid (aqueous solution) used for the first stage treatment may be 70 wt%. In other words, in the first stage, the temperature of the concentrated nitric acid (aqueous solution) having a concentration of 70 wt% in which the substrate 10 is immersed is heated to near or to the boiling point, and then in the second stage, the substrate 10 is substantially reduced. Even when immersed in azeotropic nitric acid or azeotropic nitric acid, the same effects as described above can be obtained.

[0036] Further, when a natural oxide film is formed on the surface of the substrate 10 before the heat treatment in the hydrogen atmosphere described above, for example, in a dilute hydrofluoric acid solution having a concentration of 0.8 vol% for about 5 minutes. The natural oxide film is completely removed by immersing and rinsing (cleaning) with ultrapure water for 5 minutes.

FIG. 3 is a cross-sectional view (photograph) obtained by TEM analysis. It can be seen that the interface between the surface of the substrate 10 and the film 51 formed by the above-described treatment is extremely smooth. From this sectional view, it can be seen that the thickness t of the film in this embodiment is about 21 nm.

[0038] Next, the film formed on the above-mentioned silicon carbide substrate was measured with an X-ray photoelectron spectrum (XPS) measuring device, and the characteristic diagram of Fig. 4A was obtained. From this result, it was found that the composition of this film was a film mainly composed of silicon dioxide (SiO 2).

2

[0039] FIG. 4B is an enlarged view of the coupled energy region in the vicinity of the 2p orbit of Si in the same XPS measurement apparatus. Here, for comparison, the film formed on the surface of the base material when the heat treatment in the hydrogen atmosphere is not performed and the other treatment conditions are the same is also shown. Specifically, (a) is a measurement result of a film (comparative example) that was not subjected to the heat treatment in the hydrogen atmosphere described above, and (b) is a film formed in the present embodiment. [0040] As shown in this figure, a peak in the vicinity of lOleV indicating Si—C bonds was not observed in the film (b) formed according to this embodiment, but was observed only in the film ω of the comparative example. This indicates that the film (b) is thicker than the film ω. Here, the film thickness of the film (a) was about 13 nm from the area intensity ratio between the Si—c bond peak and the peak near 104 eV indicating the Si—O bond. Therefore, compared with the result of FIG. 3, the film formation rate of the film formed by this embodiment is 1.6 times or more compared with the case where the heat treatment is not performed in the hydrogen atmosphere. This is because hydrogen penetrates into the inside of the substrate and weakens the bond, and also promotes the oxidizing power of nitric acid to act strongly on Si on the surface of the substrate, or Si on the surface of the substrate in contact with the nitric acid solution. This is thought to be due to the fact that the oxidation reaction is promoted by improving the activity of the catalyst. Although the detailed mechanism has not yet been elucidated, it goes without saying that the technical effect of significantly increasing the deposition rate disclosed in this embodiment is a significant advance in the sense of commercializing the above-described processing.

[0041] <Second Embodiment>

Electrode metal films (metal-containing films) 62 and 63 were formed on both surfaces of the structure 500 formed by the method according to the first embodiment. Thereafter, the metal film 62 on the side on which the insulating film 51 is formed is patterned into a desired electrode shape (circular with a diameter of 3 mm) by a known photolithography process, as shown in FIG. 2B. A new MOS capacitor 600 was manufactured. This metal film is formed by depositing an A1 alloy for electrodes (aluminum (A1) alloy containing about 1% by weight of silicon (Si)) to a film thickness of about 200 nm by a well-known resistance heat treatment vapor deposition method. (Hereinafter, this type of metal film electrode is simply referred to as A1 electrode). Here, the metal film for the electrode is not limited to the A1 electrode, but may be another metal. Further, a polysilicon electrode can be used instead of the electrode made of the metal film.

FIG. 5 is a C V characteristic diagram showing the relationship between the capacitance (C) of the MOS capacitor of this embodiment and the applied voltage (V). As can be seen from this characteristic diagram, a sufficient capacitance (capacitance) was obtained. In addition, from this characteristic diagram, it can be seen that no good properties due to the presence of interface states were observed, and that good CV characteristics were achieved.

[0043] The thickness of the film calculated from the CV characteristics was found to be 21.3 nm when the film composition was typical silicon dioxide (Si 2 O 3). This is the TEM analysis of Figure 3. It is in good agreement with the measurement results based on the cross-sectional view (photo).

FIG. 6 is a relationship between the current (I) and the applied voltage (V), that is, an IV characteristic diagram of the MOS capacitor manufactured in this embodiment. The dielectric breakdown voltage is about 25V as shown by this characteristic power and power, and from this point of view as well, the high insulation property of the film (film mainly composed of silicon dioxide) formed by this embodiment Was confirmed.

Further, FIG. 7 shows an IV characteristic diagram regarding the voltage dependence of the leakage current value. Here, a characteristic diagram of the MOS capacitor (comparative example) manufactured without performing the heat treatment in the atmosphere containing hydrogen shown in the previous embodiment is shown in (a), and the MOS capacitor manufactured in this embodiment is shown in FIG. The characteristic diagram of is shown in (b). As is apparent from this graphic power, the leakage current value was significantly reduced by performing the heat treatment in an atmosphere containing hydrogen. This significant reduction in leakage current proves that even a substrate with a high interface state density, such as silicon carbide, or a substrate with poor flatness can function satisfactorily as a semiconductor device with an ultrathin film. It was. In particular, when the present invention is applied to a MOS type transistor using silicon carbide, it can also be used as an insulating film used for a high frequency transistor.

[0046] Forces that have specifically described the embodiments of the present invention so far. The above-described embodiments are merely examples for carrying out the present invention. For example, in order to achieve the effects of the present invention, it is not always necessary to immerse the target substrate surface in an oxidizing solution. Specifically, using a processing apparatus 300 as shown in FIG. 1C, the substrate 10 and the oxidizing solution 22 are placed in a predetermined container 34, and the container 34 is heated by the heater 36 to evaporate the oxidizing solution 22. It may be allowed. Thus, since the substrate 10 is exposed to the vapor 32, the same effect as in the previous embodiment is achieved. At this time, fresh steam 32 can always be exposed to the substrate 10 by appropriately evacuating from the exhaust pump. In addition, using a processing apparatus 400 as shown in FIG. 1D, an oxidizing solution mist 42 may be sprayed to the substrate 10 contained in a predetermined container 44 by the sprayer 46. In this case, the mist 42 may be a vapor of an oxidizing solution. For example, the mist 42 may be sprayed in the form of a mist even if it is at room temperature and does not reach the boiling point of the oxidizing solution. It is effective for.

[0047] In the above-described embodiment, high-concentration nitric acid having a concentration of 40 wt% is used. Instead, perchloric acid, sulfuric acid, ozone-dissolved water, hydrogen peroxide solution, hydrochloric acid and hydrogen peroxide solution, and Mixed solution Liquid, 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, and solution having at least one oxidizing property selected from the group of aqua regia Or a mist of the solution, or vapor thereof. Even with these solutions, the same effects as those of the present invention are exhibited.

[0048] In the above-described embodiment, boiling nitric acid having a nitric acid concentration of 68 wt% (so-called azeotropic nitric acid) is used. Instead, a solution of azeotropic perchloric acid, or its Solution mist (mist) or its vapor can also be used. If an azeotropic mixture of water and strong acid is used as the high-concentration oxidizing solution and the azeotropic state is maintained, the concentration of each of the solution and the vapor becomes constant. Therefore, the use of an azeotrope is preferable in that the thickness of the film formed on the substrate depends on the processing time, and the film thickness can be controlled by time management.

In the above-described embodiment, 3C—SiC (cubic silicon carbide) is used as the base material. However, the present invention uses hexagonal silicon carbide (4H—SiC or 6H SiC) as the base material. The same effect as the effect of the present invention can be obtained when using. Furthermore, according to the present invention, a silicon carbide other than the above-mentioned 3C-SiC (cubic silicon carbide) and hexagonal silicon carbide (4H-SiC or 6H-SiC), silicon and polysilicon are selected. An insulating film having the same effect as at least a part of the effect of the present invention is also formed on the base material.

[0050] Further, since the present invention enables the formation of a high-performance insulating film by low-temperature treatment, a semiconductor film formed on the surface of a resin substrate is also used as a base material on which the insulating film is to be formed. included. For example, the present invention can be applied to a so-called flexible substrate. Accordingly, all modifications that come within the spirit and scope of the present invention are intended to be included within the scope of the following claims.

Claims

The scope of the claims

[I] After heating at least the substrate surface in an atmosphere containing hydrogen, the substrate surface is immersed in an oxidizing solution, or the solution is sprayed on the substrate surface, or the substrate surface A method for forming an insulating film on the surface of a substrate, which comprises a step of exposing the substrate to vapor of the solution.

[2] The oxidizing solution 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. 2. The method for forming an insulating film on the substrate surface according to claim 1, wherein the insulating film is at least one solution selected from the group consisting of a mixed solution of hydrogen peroxide and a mixture of sulfuric acid and nitric acid, and aqua regia.

[3] The heating temperature in the atmosphere is 200 ° C or higher and 600 ° C or lower, and the oxidizing solution is a nitric acid solution having a concentration of 20% or higher. Method.

[4] The method for forming an insulating film on the substrate surface according to [1], wherein the hydrogen concentration is 75 vol% or more.

5. The method for forming an insulating film on the surface of the base material according to claim 1, wherein the base material is selected from the group consisting of silicon carbide, silicon, and polysilicon.

6. The substrate surface according to claim 1, wherein the insulating film is mainly silicon dioxide (SiO 2).

2

Insulating film forming method.

7. The method for forming an insulating film on a substrate surface according to claim 1, wherein the oxidizing solution is hot nitric acid heated near or at the boiling point.

8. The method for forming an insulating film on a substrate surface according to claim 1, wherein the oxidizing solution is hot nitric acid heated from room temperature to near or to the boiling point.

[9] The substrate surface according to claim 1, wherein the oxidizing solution is at least two kinds of nitric acid having a predetermined concentration near or at a boiling point and nitric acid in a substantially azeotropic state or azeotropic state. Insulating film forming method.

[10] The insulating film formation on the substrate surface according to [1], wherein the oxidizing solution is a solution heated from an arbitrary concentration of nitric acid to room temperature or substantially azeotropic nitric acid. Method.

[II] Manufacture of a semiconductor device having a step of forming an insulating film by the method according to claim 1 Method.

12. A semiconductor device comprising an insulating film formed by the method according to claim 1.

[13] A means for heating at least the substrate surface in an atmosphere containing hydrogen, and then immersing the substrate surface in an oxidizing solution or spraying the solution on the substrate surface, An apparatus for forming an insulating film on a surface of a base material, comprising a step of exposing the surface of the base material to vapor of the solution.

[14] A method for treating a surface of a silicon carbide substrate, comprising a step of heating at least the surface of the silicon carbide substrate at 200 ° C. to 600 ° C. in an atmosphere containing hydrogen.

15. The surface treatment method for a silicon carbide substrate according to claim 14, wherein the hydrogen concentration is 75 vol% or more.

[16] A silicon carbide substrate having a root mean square roughness (Rq) of 0.5 nm or less formed by the method according to claim 14.