JP7576352B2 - Method for manufacturing MIS type semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing an MIS-type semiconductor device, and in particular to a method for manufacturing an MIS-type semiconductor device that uses a diamond semiconductor and is safe, energy-saving, has high mobility, and is suitable for high-speed operation.

Semiconducting diamond has several outstanding physical properties, such as a wide band gap energy (5.47 eV), a low dielectric constant (5.7), a high breakdown field strength (10 MV/cm), a high carrier saturation velocity (1.5-2.7×10 ⁷ cm/s and 0.85-1.2×10 ⁷ cm/s for electrons and holes, respectively), a high thermal conductivity (22 W/cm·K) and high carrier mobility (4500 cm ² /V·s and 3800 cm ² /V·s for electrons and holes, respectively), where the above property values are at room temperature.
For this reason, electronic devices using diamond as a semiconductor are expected to exhibit high-power operation, high-speed and high-frequency operation, high voltage resistance, and high thermal limit.
In particular, MIS (Metal Insulator Semiconductor) type semiconductor devices using diamond as a semiconductor have been attracting attention as core elements for constructing high-performance inverters and high-output high-frequency amplifiers.

Diamond semiconductors have higher carrier mobility than silicon (Si) and silicon carbide (SiC), which are currently the mainstream materials used for power devices. Due to this high mobility, MIS-type semiconductor devices that use diamond as a semiconductor have the potential to lower the on-resistance, suppress losses, and shorten switching times, allowing elements to operate at high speeds.

In recent years, hydrogen-terminated diamond semiconductors have been actively studied (see Non-Patent Document 1).
One of the reasons for this is that in diamond semiconductors, the activation energy of dopants is large, making it difficult to achieve both high carrier density and mobility.
Another factor that can be cited is that when diamond is produced by vapor phase synthesis, the surface of the diamond is automatically almost completely hydrogen-terminated due to hydrogen atoms, which are an essential process gas in the vapor phase synthesis process.
Hydrogen-terminated diamond semiconductors have the advantage in terms of manufacturing, in that the number of processes can be reduced, and because hydrogen termination is almost complete, they also have the advantage of being easy to obtain high quality.
When the surface of a diamond semiconductor is hydrogen-terminated, an electrically conductive region is formed in the vicinity of the surface of the diamond semiconductor, and the diamond semiconductor becomes a p-type semiconductor.

Recent research has suggested that the occurrence of electrical conduction near the surface of a hydrogen-terminated diamond semiconductor is due to the contribution of negative charges adsorbed on the surface of the diamond semiconductor or present in the insulating film formed in contact with the diamond semiconductor. Possible sources of this negative charge include, for example, adsorbed gases such as nitrogen dioxide ( _NO2 ) and ozone ( _O3 ), and solids such as tungsten oxide ( _WO3 ), molybdenum oxide ( _{MoO3 )} , vanadium oxide ( _V2O5 ), niobium oxide ( _Nb2O3 ) _, and _aluminum oxide ( _Al2O3 ) (Non-Patent Document 2).
Non-Patent Document 3 discloses that unoccupied levels due to oxygen point defects and Al deficiencies in _{an Al2O3} film formed on the surface of a diamond become negatively charged, inducing holes near the diamond surface and resulting in electrical conduction.
Furthermore, Non-Patent Document 4 discloses an example in which a diamond is exposed to _NO2 gas in order to accumulate a high concentration of holes near the surface of the diamond, and then sealed with an _{Al2O3 film} to fabricate a FET (Field Effect Transistor).

IEEE Electron Device Letters, 39, 1373 (2018) Phys. Status Solidi A, 1800681 (2018) Scientific Reports, 7, 42368 (2017) Jpn. J. Appl. Phys. ,56,01AA01(2017) APL Materials, 6, 111105 (2018) Phys. Status Solidi RRL, 1700401 (2018)

As described above, diamond semiconductors have excellent material properties for use in MIS type semiconductor devices, and hydrogen termination is helping to solve problems in productivity and quality.
However, when a MIS-type semiconductor device using a hydrogen-terminated diamond semiconductor layer was manufactured, the manufactured MIS-type semiconductor device had a problem that the mobility of holes was insufficient and did not contribute to low power consumption and high-speed operation. In addition, the flow of current when no voltage is applied is undesirable in terms of power consumption and safety, but the reduction of this current and the improvement of mobility could not be achieved at the same time.

The problem that this invention aims to solve is to provide a method for manufacturing a MIS-type semiconductor device using diamond semiconductors that is safe, energy-saving, and has high mobility and is suitable for high-speed operation.

The configuration of the present invention is shown below.
(Configuration 1)
forming a semiconductor layer having a first major surface comprised of hydrogen-terminated diamond;
forming an insulator layer in contact with at least a portion of the hydrogen-terminated surface of the semiconductor layer;
forming a conductive layer on at least a portion of the insulating layer;
A method for manufacturing a MIS type semiconductor device, wherein the atmosphere during the period from immediately after forming the semiconductor layer to immediately before forming the insulator layer is any one selected from the group consisting of vacuum, hydrogen gas, an inert gas, and hydrogen gas with an inert gas added thereto.
(Configuration 2)
preparing a member having a first main surface on which at least a portion of a semiconductor layer made of diamond is exposed;
hydrogen treatment of at least a portion of the exposed portion of the semiconductor layer;
forming an insulator layer in contact with at least a portion of the hydrogen-treated portion of the semiconductor layer;
forming a conductive layer on at least a portion of the insulating layer;
A method for manufacturing a MIS type semiconductor device, wherein the atmosphere during the period from immediately after the hydrogen treatment to immediately before the formation of the insulator layer is any one selected from the group consisting of vacuum, hydrogen gas, an inert gas, and hydrogen gas with an inert gas added.
(Configuration 3)
3. The method for manufacturing a MIS type semiconductor device according to structure 1 or 2, wherein the atmosphere for forming the insulator layer is any one selected from the group consisting of vacuum, hydrogen gas, inert gas, and hydrogen gas with an inert gas added thereto.
(Configuration 4)
4. The method for manufacturing a MIS type semiconductor device according to any one of claims 1 to 3, wherein the insulating layer is made of boron nitride.
(Configuration 5)
5. The method for manufacturing a MIS type semiconductor device according to any one of claims 1 to 4, wherein the insulating layer is made of a single crystal of boron nitride.
(Configuration 6)
6. The method for manufacturing a MIS type semiconductor device according to any one of configurations 1 to 5, wherein the insulating layer is made of hexagonal boron nitride (h-BN).
(Configuration 7)
7. The method for manufacturing a MIS type semiconductor device according to any one of configurations 1 to 6, wherein a density of charged impurities present at the interface between the semiconductor layer and the insulator layer is 0 cm ^-2 or more and 5×10 ¹¹ cm ^-2 or less.
(Configuration 8)
7. The method for manufacturing a MIS type semiconductor device according to any one of configurations 1 to 6, wherein a density of charged impurities present at the interface between the semiconductor layer and the insulator layer is 0 cm ^-2 or more and 1×10 ¹¹ cm ^-2 or less.
(Configuration 9)
9. The method for manufacturing a MIS type semiconductor device according to any one of configurations 1 to 8, wherein the inert gas is argon gas.
(Configuration 10)
3. The method for manufacturing an MIS type semiconductor device according to claim 1, wherein the pressure of the atmosphere is atmospheric pressure.

The present invention makes it possible to provide a manufacturing method for a MIS-type semiconductor device using a diamond semiconductor that is safe, energy-saving, and has high mobility and is suitable for high-speed operation.

1 is a cross-sectional view showing a structure of a MIS type semiconductor device according to the present invention; 1 is a bird's-eye view showing the crystal structures of a semiconductor layer and a gate insulator layer according to the present invention. 1A to 1C are cross-sectional views showing a manufacturing process of the MIS type semiconductor device of the present invention; 1A to 1C are cross-sectional views showing a manufacturing process of the MIS type semiconductor device of the present invention; FIG. 2 is a flow chart illustrating a manufacturing process of the MIS type semiconductor device of the present invention. FIG. 2 is a flow chart illustrating a manufacturing process of the MIS type semiconductor device of the present invention. 1A is a cross-sectional view showing the structure of the MIS-type semiconductor device of Example 1, in which (a) is a plan view seen from above, (b) is a cross-sectional view taken along the line connecting A and A' in (a), and (c) is a cross-sectional view taken along the line connecting B and B' in (a). 3A to 3C are cross-sectional views showing a manufacturing process of the MIS semiconductor device according to the first embodiment; 3A to 3C are cross-sectional views showing a manufacturing process of the MIS semiconductor device according to the first embodiment; 3A to 3C are cross-sectional views showing a manufacturing process of the MIS semiconductor device according to the first embodiment; 3A to 3C are cross-sectional views showing a manufacturing process of the MIS semiconductor device according to the first embodiment; 3A to 3C are cross-sectional views showing a manufacturing process of the MIS semiconductor device according to the first embodiment; 3A to 3C are cross-sectional views showing a manufacturing process of the MIS semiconductor device according to the first embodiment; FIG. 2 is a schematic diagram of a processing apparatus used in Example 1. FIG. 2 is a schematic diagram of a processing apparatus used in Example 1. 3 is a top view photograph of the MIS type semiconductor device fabricated in Example 1. FIG. 4 is a characteristic diagram showing the electrical characteristics of the MIS type semiconductor device fabricated in Example 1. FIG. 4 is a characteristic diagram showing the electrical characteristics of the MIS type semiconductor device fabricated in Example 1. FIG. 4 is a characteristic diagram showing the electrical characteristics of the MIS type semiconductor device fabricated in Example 1. FIG. 4 is a characteristic diagram showing the electrical characteristics of the MIS type semiconductor device fabricated in Example 1. FIG. 4 is a characteristic diagram showing the electrical characteristics of the MIS type semiconductor device fabricated in Example 1. FIG. 4 is a characteristic diagram showing the electrical characteristics of the MIS type semiconductor device fabricated in Example 1. FIG. 4 is a characteristic diagram showing the electrical characteristics of the MIS type semiconductor device fabricated in Example 1. FIG. 4 is a characteristic diagram showing the electrical characteristics of the MIS type semiconductor device fabricated in Example 1.

(Embodiment 1)
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

<Concept>
As mentioned above, in the case of hydrogen-terminated diamond semiconductors, it has been believed that negative charges attached to the surface of the diamond semiconductor or in the insulating film in contact with the diamond semiconductor are necessary for electrical conduction near the hydrogen-terminated semiconductor surface.
On the other hand, the inventors considered that this negative charge is not necessarily necessary, and rather that the negative charge reduces the mobility of charge carriers by Coulomb scattering and becomes a factor in causing normally-on operation (i.e., a positive threshold voltage V _TH ). Therefore, they found that by forming an insulating film in contact with a hydrogen-terminated diamond semiconductor without exposing it to the atmosphere after forming the hydrogen-terminated diamond surface, it is possible to reduce the negative charge density and achieve both high carrier mobility (hole mobility) and a negative threshold voltage V _TH .
In the present invention, the threshold voltage _VTH refers to the value of the gate voltage _V when, in a MIS semiconductor device, a characteristic curve of the square root of the absolute value of the drain current I _D flowing between the source and drain (|I _D | ^1/2 ) versus the gate voltage V _G applied to the gate relative to the source is linearly approximated and extrapolated to I _D = 0.

Here, the material of the gate insulating film is not limited, and examples thereof include a single layer film made of boron nitride, aluminum oxide, silicon oxide, silicon oxynitride, hafnium oxide, titanium oxide, tantalum oxide, yttrium oxide, zirconium oxide, lanthanum aluminum oxide, and calcium fluoride, or a composite film made of these films.
Among these, the gate insulating film is preferably made of boron nitride, more preferably of single crystal boron nitride, and even more preferably of hexagonal boron nitride (h-BN).When the insulating film is made into a composite film, the film on the surface in contact with the hydrogen-terminated diamond layer is preferably made of boron nitride, more preferably of single crystal boron nitride, and even more preferably of hexagonal boron nitride (h-BN).
When boron nitride, preferably single crystal boron nitride, and more preferably hexagonal boron nitride (h-BN), is used as the gate insulating film, the hole mobility can be further increased, and the threshold voltage V _TH becomes a larger negative voltage, thereby improving the controllability.

As a result of detailed investigations using experiments and simulations, in the method of the present invention, the negative charges attached to the surface of the diamond semiconductor and in the insulating film in contact with the diamond semiconductor are small in the electric conduction near the hydrogen-terminated semiconductor surface, the conduction of the diamond semiconductor layer near the hydrogen-terminated surface can be controlled by the voltage applied to the gate, and scattering due to negative charges can be suppressed.In addition, for example, when h-BN is used as the gate insulating film, the mobility is as high as 5×10 ² cm ² V ^-1 s ^-1 or more.

In a p-type MIS semiconductor device in which the threshold voltage _VTH is a negative potential, the drain current _ID does not necessarily become 0 when the gate voltage V _G is 0. If the drain current _ID characteristic with respect to the gate voltage V _G changes to have a tail near V _G = 0, that is, if the characteristic curve of |I _D | ^1/2 deviates from the approximation line near I _D = 0, the drain current _ID may flow at V _G = 0.

However, in the configuration of the present invention, for example, when hexagonal boron nitride (h-BN) is used as the gate insulating film, the approximation line of |I _D | ^1/2 closely matches the actual measurement of |I _D | ^1/2 , and the drain current I _D is less than 4×10 ^-4 mA·mm ^-1 when V _G =0. That is, the MIS-type semiconductor device of the present invention has a characteristic suitable for energy saving, that is, no current flows when no voltage is applied to the gate electrode. In the standby state where no voltage is applied to the gate electrode, no drain current I _D flows, so it is also excellent in terms of safety. In addition, since the hole mobility is high as described above, the on-resistance can be reduced, which suppresses the conduction loss, resulting in energy saving even during operation.

The inventor also discovered that, as a method of forming a gate insulating film in contact with the hydrogen-terminated diamond semiconductor layer surface and making the threshold voltage _VTH a negative voltage, the atmosphere between the hydrogen-terminated semiconductor layer forming step and the insulator layer forming step may be any one selected from the group consisting of vacuum, hydrogen gas, inert gas, and hydrogen gas with inert gas added thereto. Note that, as the steps between the hydrogen-terminated semiconductor layer forming step and the insulator layer forming step, for example, a sample transport step and a sample temporary storage step may be mentioned. Here, as the insulating film, as mentioned above, boron nitride is preferable, single crystal boron nitride is more preferable, and hexagonal boron nitride (h-BN) is even more preferable.

<Structure and Features>
1, the MIS type semiconductor device 101 of the present invention has a diamond substrate 21, a diamond semiconductor layer 22, a gate insulator layer (gate insulating film) 23, and a conductive layer (gate electrode) 24 as basic components, and also has a source electrode and its wiring 28, a drain electrode and its wiring 29, a gate electrode wiring 27, an insulating film 25, and a low resistance layer 26. At least the first main surface of the diamond semiconductor layer 22 is hydrogen-terminated as described later.
Here, even if the substrate is other than diamond, a thin film made of diamond may be formed on the substrate, and this may be used as the diamond semiconductor layer 22. Also, the diamond substrate 21 may be used as the semiconductor layer, and the surface layer of the diamond substrate 21 may be used as the diamond semiconductor layer 22. What is essential is that the semiconductor layer made of diamond is in contact with the gate insulating film 23. Here, the semiconductor layer made of diamond (diamond semiconductor layer) 22 may contain a dopant.

The present invention relates to an MIS-type semiconductor device having a semiconductor layer made of diamond, a material with excellent electrical properties. One of the characteristics of the structure of the MIS-type semiconductor device of the present invention that enhances its effectiveness is that the gate insulator layer 23 is made of boron nitride, more preferably made of single crystal boron nitride, and even more preferably made of hexagonal boron nitride (h-BN).

Known boron nitride structures include amorphous boron nitride (a-BN) with an amorphous structure, turbostratic boron nitride (t-BN) with a disordered stacking structure in the c-axis direction, cubic boron nitride (c-BN) with a cubic zinc-blende structure, hexagonal boron nitride (h-BN) with a hexagonal graphite structure, and wurtzite boron nitride (w-BN) with a hexagonal wurtzite structure.
Of these boron nitrides (BN), hexagonal boron nitride (h-BN) is most preferable for the gate insulator layer 23 from the viewpoint of reducing charge traps in the gate insulator layer 23, and it is more preferable that h-BN is in the form of a single crystal.

In the MIS-type semiconductor devices (diamond field-effect transistors) using diamond semiconductors reported so far, the gate insulator layer (gate insulating film) is mostly an amorphous film, and has been formed mainly by vapor deposition or atomic layer deposition (ALD). Gate insulator layers formed by these methods have a relatively high charge trap density due to atomic vacancies, and a relatively high interface state is formed at the interface with the diamond semiconductor layer. Charges captured in such traps (states) are a factor in reducing carrier mobility.

Diamond is made up of a crystal in which each carbon atom is covalently bonded to the four surrounding atoms. On the surface of diamond, there are extra bonds. These dangling bonds are unstable and act as surface states.
The dangling bonds can be stabilized by bonding with hydrogen, a state called hydrogen termination.
For example, the surface of diamond produced by chemical vapor deposition is hydrogen-terminated because it is exposed to hydrogen plasma during synthesis. Using such a hydrogen-terminated diamond surface can reduce the surface state density on the diamond side.
On the other hand, the surface of h-BN has no dangling bonds due to its structure. Therefore, the interface state density at the junction interface between h-BN and hydrogen-terminated diamond is low. Furthermore, the trap density in the insulator layer (insulator film) made of single crystal h-BN is small. For these reasons, carrier scattering due to charges captured in traps or interface states in the insulator layer can be reduced.

In addition, h-BN has a large dielectric breakdown field (parallel to the c-axis) of approximately 12 MV/cm, which induces high-density carriers, resulting in low on-resistance. Furthermore, the lattice mismatch between h-BN and the hydrogen-terminated diamond (111) surface is approximately 0.7%, which is suitable for forming an interface with few lattice defects and distortion. This also contributes to improving the characteristics of MIS-type semiconductor devices. For reference, a bird's-eye view schematic diagram of the crystal structure of h-BN and hydrogen-terminated diamond crystal (111) is shown in Figure 2. In Figure 2, 11 represents carbon, 12 represents hydrogen, 13 represents boron, and 14 represents nitrogen atoms.

The gate insulator layer 23 preferably has a thickness of one atomic pair layer of boron and nitrogen or more and 300 nm or less, and more preferably has a thickness of 1 nm or more and 100 nm or less.
A dense film of one atomic pair layer or more suppresses leakage current and is more likely to function as a gate insulator layer. In order to suppress leakage current including tunnel current, a thickness of 1 nm or more is preferable.
Furthermore, when the thickness of the gate insulating layer 23 is 300 nm or less, it becomes easier to obtain a sufficient capacitance as an MIS type semiconductor device.

The diamond semiconductor layer 22 is preferably a single crystal with a (100) or (111) crystal face.

The density of the charged impurities present at the interface between the diamond semiconductor layer 22 and the gate insulator layer 23 (interface concentration) is preferably 0 cm ^-2 or more and ^5x1011 cm ^-2 or less, more preferably 0 cm ^-2 or more and ^1x1011 cm ^-2 or less. When the density of the charged impurities is within this range, scattering of holes moving through the channel layer formed near the hydrogen-terminated surface of the diamond semiconductor layer 22 by the charged impurities is suppressed, and it is possible to provide a MIS-type semiconductor device 101 with high mobility.
Here, the MIS semiconductor device 101 induces holes in the channel layer by a negative potential applied to the gate electrode 24. On the other hand, when no voltage is applied to the gate electrode 24, the device is shut off and the MIS semiconductor device 101 operates normally off. When the density of the charged impurities is within the above range, the number of holes induced by the charged impurities is extremely small, and therefore the leakage current between the source and drain when no voltage is applied to the gate electrode 24 is very small.

The inventors have found that it is possible to keep the density of charged impurities within the range of 0 cm -2 to 5 x 10 ¹¹ cm ^-2 by a relatively simple process of placing the sample in a vacuum or in an inert gas environment such as Ar gas after hydrogen ^termination until the hydrogen-terminated surface is covered with the gate insulator layer 23. It is possible to keep the density of charged impurities within the above range without requiring washing, cleaning heat treatment, or surface treatment.

Both diamond and h-BN have wide bandgaps (5.47 eV and 5.97 eV), making them suitable for high-temperature operation. h-BN has a high thermal conductivity of 4 W/cm K at room temperature, which is comparable to that of copper, and this, combined with the high thermal conductivity of diamond (22 W/cm K at room temperature), contributes to excellent heat dissipation from the channel. In addition, h-BN is known to act as a coating material that prevents oxidation at high temperatures of 1000°C. Therefore, it also functions to protect the hydrogen termination on the diamond surface at high temperatures. On the other hand, the low dielectric constants of diamond and h-BN (5.7 and 5.1 (c-axis parallel)) are desirable characteristics for high-speed and high-frequency operation.

It is preferable that the gate insulator layer 23 be in direct contact with the surface of the terminated diamond semiconductor layer 22, without any layers of water, hydrocarbons, resist residues, etc. sandwiched between them. This is because interfacial states are likely to occur if such layers are sandwiched between them.

In the conventional structure using _an amorphous film such as _Al2O3 as the gate insulator layer 23, there is a tendency for many traps (charge traps) to be included in the gate insulator layer 23 and at the interface between the gate insulator layer 23 and the diamond semiconductor layer 22. Therefore, carrier conduction is scattered, and carrier mobility is low.
On the other hand, in the structure of the present invention in which boron nitride, preferably single crystal boron nitride, more preferably h-BN, and even more preferably single crystal h-BN is used as the gate insulator layer (gate insulating film), there tends to be fewer charge traps in the gate insulator layer 23. Therefore, carrier conduction is less scattered, and high carrier mobility can be obtained.

The diamond substrate 21 preferably has few crystal defects, high cleanliness, and a flat, smooth surface so that the diamond semiconductor layer 22 formed thereon will be a high-quality crystal with few defects. In addition, to reduce the effects of surface roughness scattering, it is preferable that the surface of the semiconductor layer is also flat and smooth.

The gate electrode 24 is made of a conductive material having a work function such that the threshold voltage V _TH is a negative voltage. Specifically, conductive films such as metal, graphite (C), or polysilicon to which a dopant is added can be mentioned. Examples of metals include copper (Cu), tungsten (W), titanium (Ti), aluminum (Al), chromium (Cr), and tantalum (Ta). In addition, alloys such as AlCu, CuNiFe, and NiCr, silicides and polycides such as WSi and TiSi, and metal compounds such as WN, TiN, CrN, and TaN can also be used. The gate electrode 24 can be made of an appropriate material selected from these materials, taking into account the conductivity, work function, processability, and the like.
The threshold voltage V _TH depends on the material of the gate electrode 24, the material and thickness of the gate insulator layer 23, the material of the semiconductor channel layer, impurities and their concentrations, and the like.
Furthermore, when the MIS semiconductor device of the present invention is used as an integrated circuit, various heat treatments are added as part of the integration, and the materials must be selected taking into consideration the diffusion of the materials in these heat treatments.

The source electrode and its wiring 28, the drain electrode and its wiring 29, and the gate electrode wiring 27 are made of a conductive film such as metal, graphite, or polysilicon to which a dopant is added. Examples of metals include gold (Au), silver (Ag), Cu, platinum (Pt), palladium (Pd), W, Ti, Al, Cr, and Ta. In addition, alloys such as AlCu, CuNiFe, and NiCr, polycides using W or Ti, and metal compounds such as WN, TiN, CrN, and TaN can also be used.
These conductive films are preferably capable of making ohmic contact at the part in contact with the diamond semiconductor layer 22. For example, it is preferable to use a metal having a high work function such as gold (Au) or palladium (Pd) as the conductive film. These high work function metals have the characteristic of being capable of making ohmic contact by direct contact. Titanium (Ti) can also be used. Here, it is preferable to anneal Ti to react with diamond and form TiC. On the other hand, since Ti is easily oxidized, when making electrical contact with the diamond semiconductor layer 22, it is preferable to make a conductive film structure in which Ti is laminated from the diamond semiconductor layer 22 side, and a material such as Pt, Au or W is laminated thereon.

In addition, in order to ensure ohmic contact with the source electrode 28 and the drain electrode 29 and to reduce the resistance of the diamond semiconductor layer 22 other than the channel portion, it is preferable to form a low-resistance layer 26 at the interface between the diamond semiconductor layer 22 and the source electrode 28 or the drain electrode 29. For example, when the source electrode 28 and the drain electrode 29 are made of Ti, an example of the low-resistance layer is TiC formed by annealing.

The insulating film 25 provides electrical insulation and prevents the diffusion of moisture and impurities, thereby playing a role in the stable operation of the MIS semiconductor device 101. Examples of materials for the insulating film 25 include a silicon oxide ( _SiO2 ) film, a silicon nitride (SiN) film, a silicon oxynitride (SiNO) film, _a silicon carbide (SiC) film, a silicon carbonitride (SiCN) film, a silicon carbonitride oxide (SiCNO) film, an alumina ( _Al2O3 ) film, a boron nitride (BN) film, and an organic film such as polyimide.

<Production Method>
Next, a method for manufacturing this MIS type semiconductor device 101 will be described with reference to FIGS. 3 and 4 showing the cross-sectional structure and FIG. 5 showing a flow chart.
3A, a diamond substrate 21 is prepared. As the diamond substrate, for example, a Ib type or IIa type substrate with a crystal face of 100 or 111 can be preferably used.
Here, the surface of diamond substrate 21 is preferably flat (planar) and atomic level smooth. For the electrical characteristics of field effect transistor, the flatness and smoothness of the interface between diamond semiconductor layer 22 and gate insulator layer 23 are important, and in order to make the flatness and smoothness of the interface sufficiently high, it is necessary to sufficiently increase the flatness, smoothness and cleanliness of diamond substrate 21 surface.

Thereafter, as shown in FIG. 3(b), a diamond semiconductor layer terminated with hydrogen is epitaxially grown on the diamond substrate 21 to form a hydrogen-terminated diamond semiconductor layer 22 (S1 in FIG. 5).
The hydrogen-terminated diamond semiconductor layer 22 can be formed by, for example, microwave plasma CVD (Chemical Vapor Deposition) using CH ₄ gas and H ₂ gas.
The thickness of the diamond semiconductor layer 22 is preferably 10 nm or more. If the thickness is 10 nm or more, it is possible to suppress the intrusion of impurities from the substrate, particularly in the case of an Ib substrate.

A dopant may be added to the diamond semiconductor layer 22. An example of a hole-based dopant is boron (B), and an example of an electron-based dopant is phosphorus (P). The amount of dopant added is preferably 10 ¹⁶ /cm ³ or more and 10 ¹⁹ /cm ³ or less. If the amount is less than 10 ¹⁶ /cm ³ , the effect of dopant addition is small, and if the amount exceeds 10 ¹⁹ /cm ³ , carrier scattering occurs, resulting in a decrease in performance such as mobility.

Next, immediately after the surface (at least the first main surface) of the diamond semiconductor layer 22 is hydrogen-terminated, evacuation and/or inert gas replacement is performed so that the environment in which the sample is placed is one selected from the group consisting of vacuum, hydrogen gas, inert gas, and hydrogen gas with inert gas added (S2 in FIG. 5). As the inert gas, noble gases such as Ar gas, Kr gas, and Xe gas, and _N2 gas can be mentioned. Here, this one environment selected from the group consisting of vacuum, hydrogen gas, inert gas, and hydrogen gas with inert gas added is maintained at least until just before forming the insulating film 23a described later. By doing so, the charged impurities at the interface between the diamond semiconductor layer 22 and the insulating film 23a are reduced, and high hole mobility can be obtained.

If the next step of forming the insulating film 23a is a process such as CVD that is carried out in a vacuum environment, it is efficient and preferable to keep the sample environment in a vacuum, and if the insulating film 23a is formed by bonding or the like, it is preferable to place it in an inert gas environment from the standpoint of work efficiency. In addition, Ar gas is the most preferable inert gas, taking into consideration the degree of inertness, assurance of purity, and cost.

When placed in a vacuum, the degree of vacuum is preferably about 1×10 ⁻⁵ Pa in consideration of the effect and the burden on the equipment.
When an inert gas is used, atmospheric pressure is preferable because of ease of handling. Here, atmospheric pressure refers to pressure in an atmospheric environment including low pressure, high pressure, and high altitude, as well as pressure in a glove box or the like that is pressurized to prevent outside air from being mixed in.
In addition, it is preferable that the concentration of oxygen gas ( _O2 gas) in the environment is 0.5 ppm or less, and the dew point is -80°C or less.
The surface of hydrogen-terminated diamond is chemically stable, and in this level of environment, it is possible to obtain a surface state that serves as a semiconductor layer suitable for obtaining high hole mobility with few charged impurities and little scattering of charged impurities.

After that, as shown in Fig. 3(c), an insulating film 23a is formed on the diamond semiconductor layer 22 terminated with hydrogen or the like (S3 in Fig. 5). Here, as the insulating film 23a, boron nitride is preferable, boron nitride single crystal is particularly preferable, h-BN is more preferable, and h-BN single crystal is even more preferable. Below, the case where the insulating film is boron nitride, which is highly effective, is taken as an example for explanation.
The insulating film 23a can be formed by laminating a boron nitride thin film obtained by cleavage, a chemical vapor deposition method such as thermal CVD or plasma CVD, a physical vapor deposition method such as sputtering, a physical chemical vapor deposition method, etc. Specific examples include a metal-organic chemical vapor deposition method (MOCVD: Metal-Organic Chemical Vapor Deposition) using triethylborane (TEB) and ammonia (NH ₃ ) as source gases and hydrogen (H ₂ ) as a carrier gas, and a molecular beam epitaxy method (MBE: Molecular Beam Epitaxy) using active nitrogen produced by RF plasma and boron heated and supplied by an electron gun.
In addition, when the insulating film 23a is formed by laminating a boron nitride thin film obtained by cleavage, the lamination environment is preferably any one selected from the group consisting of vacuum, hydrogen gas, inert gas, and hydrogen gas with an inert gas added thereto. That is, the environment for the formation process of the insulating film 23a is preferably any one selected from the group consisting of vacuum, hydrogen gas, inert gas, and hydrogen gas with an inert gas added thereto.

In addition, in order to remove the adsorbed matter at the interface between the diamond semiconductor layer 22 and the insulating film 23a and to clean the surface of the insulating film 23a, it is preferable to carry out annealing using a mixed gas of inert gas and hydrogen (H ₂ ) gas after forming the insulating film 23a. Here, the inert gas can be, for example, argon (Ar).

Thereafter, as shown in FIG. 3D, a gate electrode 24 is formed (S4 in FIG. 5).
The gate electrode 24 may be formed by depositing a conductive material constituting the gate electrode 24 on the insulating film 23a by sputtering, deposition, CVD, lamination, or the like, forming a resist pattern by lithography, and then etching the gate electrode 24. Dry etching is preferably used as the etching method from the viewpoint of fine processing, but wet etching can also be used. Wet etching has the advantage that it is easy to suppress damage to the MIS semiconductor device 101 being fabricated.
Alternatively, a resist pattern for lift-off may be formed on the insulating film 23a, and then a conductive material for forming the gate electrode 24 may be deposited by sputtering, evaporation, CVD or the like, followed by lift-off.

Here, examples of sputtering methods include DC sputtering and RF sputtering, with RF sputtering being more preferred from the viewpoint of throughput. Examples of deposition methods include thermal deposition and electron beam deposition. When polysilicon is used as the material for the gate electrode 24, the CVD method is preferably used as the method for forming the polysilicon film. At this time, it is preferable to add a dopant such as phosphorus (P) to reduce the resistance.

Thereafter, an insulating film 25a is formed by a sputtering method, an ALD method, a CVD method, a bonding method, or a coating method such as SOG (Spin on Glass) (FIG. 4A).
Here, since the formed insulating film 25a often contains voids and undesired water that hinder the stabilization of electrical characteristics, it is preferable to perform annealing.

Next, desired openings are formed in the insulating film 25a and the gate insulating film 23a by lithography and etching to form the insulating film 25 and the gate insulating layer (gate insulating film) 23, respectively (Figure 4(b)).

After that, a low-resistance layer 26 is formed on the exposed surface of the diamond semiconductor layer 22 at the opening, which provides ohmic contact between the electrode and the semiconductor layer and also provides low resistance (Fig. 4(c)). The low-resistance layer 26 can be obtained by depositing a metal that forms a carbide with diamond, such as Ti or Mo, and then annealing to form a metal carbide. For the hydrogen-terminated semiconductor layer, deposited high-work function metals such as Au, Pd, and Pt can be used as the low-resistance layer.

Thereafter, a conductive film is deposited, and lithography and etching are performed to form a gate electrode wiring 27, a source electrode and its wiring 28, and a drain electrode and its wiring 29 (FIG. 4(d)).
The low resistance layer 26 may be formed by annealing after forming these electrodes and/or wiring.
By the above steps, the MIS type semiconductor device 101 having the diamond semiconductor layer 22 and the gate insulator layer 23 made of h-BN is fabricated.

The MIS semiconductor device 101 of the present invention has high carrier mobility (hole mobility), consumes little power when off (standby) due to normally-off operation, and has high mutual conductance _gm and low on-resistance even when on, making it an ideal semiconductor device for energy saving with low power consumption. It is also preferable from the viewpoint of security because it barely conducts electricity during standby.
Therefore, the present invention provides a high-performance MIS type semiconductor device that combines high levels of both mobility and carrier density.

The above describes a method for fabricating a single MIS-type semiconductor device 101, but a MIS-type semiconductor device in which multiple MIS-type semiconductor devices 101 are mounted and integrated can also be fabricated in the same manner. In this case, an insulating layer is provided between each MIS-type semiconductor device 101, and element isolation is performed as necessary.

(Embodiment 2)
In the first embodiment, a method for manufacturing the MIS type semiconductor device 101 through the hydrogen-terminated diamond semiconductor layer formation step S1, that is, the step of forming the diamond semiconductor layer 22 terminated with hydrogen on the diamond substrate 21, has been described.
In the second embodiment, instead of the hydrogen-terminated diamond semiconductor layer forming step S1, as shown in FIG. 6, a diamond semiconductor exposed member preparation step S11 and a hydrogen-termination treatment step S12 are performed, and the other steps are performed in the same manner as in the first embodiment to provide a MIS type semiconductor device.

In the second embodiment, first, prepare a member with exposed diamond semiconductor (step S11).As the member with exposed diamond semiconductor, it can be exemplified by a diamond semiconductor substrate, and a member with a part of the first main surface of the diamond semiconductor exposed and a part of the conductive layer or/and an insulating layer for element isolation or the like formed.
Thereafter, at least a portion of the exposed diamond semiconductor is hydrogen-terminated (step S12).
The hydrogen termination treatment can be performed by plasma or heat treatment under hydrogen gas. For example, a MP-CVD apparatus is used, and the treatment is performed for 10 minutes under the conditions of _H2 flow rate of 500 sccm, pressure of 4 KPa, heater temperature setting of 600°C, and microwave output of 300 W.
Hereinafter, the vacuum or inert gas environment treatment (S13) may be the same as the vacuum or inert gas environment treatment (S2) in embodiment 1, the boron nitride insulator layer formation process (S14) may be the same as the boron nitride insulator layer formation process (S3) in embodiment 1, and the conductor layer formation process (S15) may be the same as the conductor layer formation process (S4) in embodiment 1.
As a result, a MIS semiconductor device having the same characteristics as those of the first embodiment can be provided.

The present invention will be described in more detail below with reference to examples. However, these examples are provided merely to aid in understanding the present invention and are not intended to limit the present invention.

Example 1
<Element structure>
The element structure of the MIS type semiconductor device 201 of the first embodiment will be described with reference to Fig. 7, which is a cross-sectional view of a main part. Fig. 7(a) is a plan view seen from above, and Fig. 7(b) and Fig. 7(c) are cross-sectional views taken along lines connecting A and A' and B and B' in Fig. 7(a), respectively. In Fig. 7, the components are simplified by using rectangles, etc., in order to make the configuration easier to understand.
The MIS type semiconductor device 201 comprises a diamond substrate 31, a hydrogen termination layer 32, a gate insulating film 33, a gate electrode 34 _G , a source electrode 37 _S , a drain electrode 37 _D , a gate electrode wiring 62 _G , a source electrode wiring 62 _S , a drain electrode wiring 62 _D and an insulating film 61.
Here, the source electrode _37S and the drain electrode _37D are composed of, from the top, a conductive film 36 made of platinum (Pt) and having a thickness of 5 nm, a conductive film 35 made of Ti and having a thickness of 5 nm, and a low resistance layer 42 made of titanium carbide (TiC) generated at the interface between the diamond substrate 31 and the Ti of the conductive film 35.
The gate insulating film 33 is made of hexagonal boron nitride (h-BN) and has a thickness of 23 nm.

The diamond substrate 31 has a hydrogen termination layer 32 in the channel region located directly below the gate insulating film 33, a low resistance layer 42 made of TiC located directly below the conductive film 35, and an oxygen termination layer 43 in the remaining surface region.

The gate electrode _34G is made of graphite having a thickness of 20 nm. A gate electrode wiring (bonding pad wiring) _62G is formed by sequentially laminating a Ti film having a thickness of 10 _nm and a Au film having a thickness of 100 nm on the gate electrode 34G.

The source is composed of a conductive film for ohmic contact (35, 36 in FIG. 7) made of 5 nm thick Ti and 5 nm thick platinum (Pt) and a source electrode wiring (bonding pad wiring) _62S . Here, the source electrode wiring _62S has a structure in which 5 nm thick Ti, 5 nm thick Pt, 10 nm thick Ti, and 100 nm thick Au are laminated in this order. In addition, a low resistance layer 42 made of TiC is formed in the boundary region between the conductive film 35 and the diamond substrate 31.
Similarly, the drain is made up of a conductive film for ohmic contact made of 5 nm thick Ti and 5 nm thick Pt (respectively 35 and 36 in FIG. 7) and a drain electrode wiring (bonding pad wiring) 62 _D. Here, the drain electrode wiring 62 _D has a structure in which 5 nm thick Ti, 5 nm thick Pt, 10 nm thick Ti, and 100 nm thick Au are laminated in this order, and a low resistance layer 42 made of TiC is formed in the boundary region between the conductive film 35 and the diamond substrate 31.

In order to sufficiently insulate the channel layer 32 from the gate electrode wiring (bonding pad wiring) 62 _G , an insulating film 61 for element isolation is formed so as to cover an edge portion (boundary between oxygen-terminated and hydrogen-terminated regions) 71 of the gate insulating film 33 where the gate electrode wiring 62 _G is formed. The insulating film 61 is also made of hexagonal boron nitride (h-BN) and has a thickness of 63 nm.

<Production Method>
The element fabrication process will be described below with reference to the cross-sectional views of Fig. 8 to Fig. 13. Here, Fig. 8-10 are cross-sectional views taken along the line connecting A and A' in Fig. 7(a), and Fig. 11-13 are cross-sectional views taken along the line connecting B and B' in Fig. 7(a).

1. Preparation of the substrate A high-temperature, high-pressure synthesis IIa (111) diamond single crystal substrate manufactured by the TISNCM Institute in Russia was prepared as the diamond substrate 31, and the substrate was cleaned by a conventional method using hot mixed acid and organic cleaning. The size of the diamond substrate 31 used here was 2.5 mm x 2.5 mm x 0.3 mm.

2. Formation of Alignment Mark Alignment marks (not shown) were formed on the diamond substrate 31 by laser lithography.
The process of forming the alignment marks will now be described.
First, the surface of the diamond substrate 31 was spin-coated with a lower layer resist PMGI-SF6S (manufactured by Microchem) and baked at 180° C. for 5 minutes. Then, a photoresist AZ-5214E (manufactured by Merck Performance Materials) was spin-coated and baked at 110° C. for 2 minutes.
Next, an alignment mark pattern was written using a high-speed maskless exposure device (DL-1000/NC2P, manufactured by Nano System Solutions). After development with 2.38% TMAH (tetramethylammonium hydroxide) for a total of 150 seconds, the substrate was washed with pure water for a total of 120 seconds, and then nitrogen was blown.

Thereafter, Ti to a thickness of 10 nm, Pt to a thickness of 15 nm, Au to a thickness of 60 nm, and Pt to a thickness of 25 nm were successively deposited by means of an electron gun type deposition apparatus.
Thereafter, the sample was immersed in NMP heated in a water bath set to 80° C., and lift-off was carried out.
Finally, the diamond substrate 31 was rinsed with acetone and IPA, and then nitrogen was blown to form alignment marks at predetermined positions on the diamond substrate 31.

3. Fabrication of Ohmic Electrode An electron beam resist gL-2000DR2.0 (manufactured by Gluon Lab) was spin-coated onto the diamond surface of the diamond substrate 31, and baked at 180° C. for 5 minutes.
Then, Espacer 300Z (Showa Denko) was spin-coated, and a pattern of an ohmic electrode was drawn using a 100 kV electron beam drawing device (ELS-7000, Elionix). After drawing, the substrate was washed with pure water for 60 seconds to remove the Espacer, and then nitrogen was blown. Then, the substrate was developed with xylene for 60 seconds, washed with IPA for 60 seconds, and nitrogen was blown to form a resist pattern 51 on the diamond substrate 31 (FIG. 8(a), FIG. 11(a)).

Next, a conductive film 35a made of Ti and having a thickness of 5 nm and a conductive film 36a made of Pt and having a thickness of 5 nm were successively deposited by an electron gun type deposition apparatus (FIGS. 8(b) and 11(b)).
Thereafter, the sample was immersed in NMP heated in a water bath set at 80° C. to perform lift-off. After rinsing with acetone and IPA, nitrogen was blown.
Thereafter, annealing was performed for 35 minutes in an _H2 atmosphere ( _H2 flow rate 500 sccm, pressure 80 Torr) in an MPCVD apparatus (Seki Technotron, AX5200-S) to form a low resistance layer 42 made of TiC at the interface between the diamond and Ti (Figures 8(c) and 11(c)). The set temperature during annealing was raised to 650°C in about 31 minutes and held at 650°C for 35 minutes.

4. Hydrogen Termination of Diamond Surface and Removal of Resist Residues Following the formation of the ohmic electrodes described above, the diamond was exposed to hydrogen plasma for 10 minutes in an MPCVD apparatus (AX5200-S, manufactured by Seki Technotron) to hydrogen-terminate the surface and remove the resist residues, forming a hydrogen-terminated layer 32 on the exposed surface of the diamond substrate 31 (FIG. 8(d) and FIG. 11(d)).
The hydrogen plasma conditions were: H ₂ flow rate 500 sccm, pressure 30 Torr, heater set temperature 600° C., and microwave output 300 W.
Further, annealing was performed for 35 minutes in a _H2 atmosphere ( _H2 flow rate 500 sccm, pressure 80 Torr) in another MPCVD apparatus (AX5000, manufactured by Seki Technotron) that can be connected to a vacuum transfer chamber. The set temperature during annealing was raised to 710°C in about 34 minutes and held at 710°C for 35 minutes.
The diamond was exposed to hydrogen plasma for 10 minutes in an MPCVD apparatus (AX5000 manufactured by Seki Technotron) to remove surface adsorbates. The hydrogen plasma conditions were _H2 flow rate of 500 sccm, pressure of 30 Torr, heater temperature setting of 670°C, and microwave output of 300 W.

The diamond substrate 31 that had been subjected to hydrogen plasma treatment was then transported to a glove box with an argon gas atmosphere via a sample transport path that was kept in vacuum, without being exposed to the atmosphere. The details are explained below with reference to Figures 14 and 15, which are cross-sectional diagrams of the device configuration.

FIG. 14 is a cross-sectional view showing an outline of a processing apparatus 1001 for performing hydrogen plasma processing.
The main components of the processing apparatus 1001 are a hydrogen termination treatment chamber 1011 and a sample transfer and temporary storage chamber 1025. The processing apparatus 1001 is broadly divided into a hydrogen termination processing section E1 mainly composed of the hydrogen termination treatment chamber 1011, and a sample transfer section E2 mainly composed of the sample transfer and temporary storage chamber 1025, and the sections E1 and E2 can be separated beyond a gate valve 1024 (the connection between the gate valve 1024 and the transfer intermediate chamber 1027).

The hydrogen termination treatment chamber 1011 is connected to a sample transfer and temporary storage chamber 1025 via two gate valves 1024 and 1026 and a transfer intermediate chamber 1027, and a sample rod 1029 allows the sample to be transferred from the hydrogen termination treatment chamber 1011 to the sample transfer and temporary storage chamber 1025. Here, the transfer intermediate chamber 1027 is provided with a flange 1028 for connecting a vacuum exhaust system, and is closed by the flange (blank flange) 1028 when the vacuum exhaust system is not connected.
A turbo exhaust set 1075 is connected to the sample transfer/temporary storage chamber 1025 via a pipe 1071, a valve 1072, a flange 1073, and a bellows pipe 1074. Here, the turbo exhaust set 1075 is a T-Station 75D (manufactured by Edwards) consisting of a turbo molecular pump and a diaphragm pump.

The hydrogen termination treatment chamber 1011 is a treatment chamber in which the exposed surface of the first main surface (diamond semiconductor layer) of the diamond substrate 31 is hydrogen-terminated by hydrogen plasma, and specifically, is the treatment chamber of the above-mentioned MPCVD apparatus (AX5000, manufactured by Seki Technotron).
The hydrogen termination chamber 1011 is connected to a turbo pump (STP-iX455, manufactured by Edwards) 1013 via a gate valve 1012, and the turbo pump 1013 is connected to a scroll pump (nXDS15i, manufactured by Edwards) 1016 via a valve 1014 and a pipe 1015. This results in a so-called oil-free vacuum pump configuration. The degree of vacuum in 1011 can be read by a vacuum gauge 1063 (ionization vacuum gauge TG200, manufactured by Ampere).

The hydrogen termination chamber 1011 is also provided with an exhaust path connected to the scroll pump 1016 via a valve 1017 and a pipe 1018 for the purpose of rough evacuation. For hydrogen termination control, valves 1019 and 1061 and a pipe 1062 are provided, and the hydrogen termination chamber 1011 is also provided with a path connecting the hydrogen termination chamber 1011 to the scroll pump 1016 via the valves 1019 and 1061 and a pipe 1062.
The hydrogen termination treatment chamber 1011 is designed so that a process gas (H ₂ gas) 1023 can be introduced through a valve 1022 .
The hydrogen termination chamber 1011 is also equipped with a Baratron vacuum gauge 1020 for monitoring the pressure inside the chamber 1011 when hydrogen termination is being performed.

FIG. 15 is a cross-sectional view showing an outline of a processing apparatus 1002 used in attaching an insulating film 33a made of h-BN to a sample.
The processing apparatus 1002 mainly comprises a bonding processing chamber (glove box) 1031 and a sample transfer and temporary storage chamber 1025. The sample transfer section E2, which mainly comprises the sample transfer and temporary storage chamber 1025, is connected to a bonding processing section E3 via a gate valve 1043, so that the sample can be transferred to the bonding processing chamber (glove box) 1031 without being exposed to the atmosphere.

Here, a vacuum exhaust system E4 is connected via a flange 1028 so that the sample is not exposed to the atmosphere in the transfer intermediate chamber 1027 when the sample is transferred from the sample transfer/temporary storage chamber 1025 to the bonding processing chamber (glove box) 1031.
The vacuum exhaust system E4 includes a chamber 1101 equipped with bellows piping 1109, 1111, a valve 1110, and a vacuum gauge (crystal/cold cathode combination gauge CC-10, manufactured by Tokyo Denshi) 1112, an angle valve 1102, a turbo pump (nEXT300D, manufactured by Edwards) 1103, a valve 1104, piping 1107, and a scroll pump (nXDS15i, manufactured by Edwards) 1105, and further includes piping 1107 and a valve 1106 for roughing the chamber 1101 with the scroll pump 1105.

The bonding process chamber 1031 is a process chamber in which an h-BN insulating film that becomes the insulating film 33a is bonded to the sample, and is connected to a pass box 1034 via a partition door 1032, and the pass box 1034 is connected to a scroll pump (nXDS15i, manufactured by Edwards) 1037 via a valve 1035 and piping 1036. The bonding process chamber 1031 is equipped with piping and a valve 1038 to enable direct evacuation by the scroll pump 1037, and the pass box 1034 is equipped with a pressure gauge 1039.

The bonding process chamber 1031 is filled with an inert gas (Ar gas) at atmospheric pressure.
Ar gas is supplied from an Ar gas cylinder 1052 to the bonding processing chamber 1031 and the pass box 1034 through a pipe 1053. Here, the pipe 1053 leading to the bonding processing chamber 1031 and the pass box 1034 is provided with valves 1054 and 1055, respectively.
This Ar gas is constantly purified by an inert gas circulation refiner 1040 connected to the bonding processing chamber 1031 via pipes 1042, 1045 and valves 1041, 1044, and is kept at an oxygen concentration of 0.5 ppm or less and a dew point of −79° C. or less. This purified Ar gas can be introduced into the sample transport section E2 via a vacuum exhaust system E4 connected via a valve 1108.
The bonding processing chamber 1031 is a so-called glove box, and is provided with butyl rubber gloves for performing bonding work while isolating the atmosphere from the outside. The bonding processing chamber 1031 is also connected to an Ar gas cylinder 1052 via a valve 1054, and to a scroll pump 1037 via a valve 1038, so that the pressure inside the bonding processing chamber 1031 can be adjusted when the hand is put into the glove. Furthermore, a microscope (not shown) is provided, and bonding work on the order of microns can be performed in an environment that is isolated from the outside in terms of atmosphere (gas). The image of the microscope can be observed on a monitor outside the bonding processing chamber 1031 without damaging the inert gas environment.
The outer wall of the bonding processing chamber 1031 is made of stainless steel and glass, and the internal volume of the bonding processing chamber 1031 is about 310 liters.

The steps after the hydrogen termination and before the h-BN bonding are shown below.
First, in a pre-processing step, the gate valves 1012, 1024, 1026 and the valve 1014 are opened, and the hydrogen termination treatment chamber 1011, the intermediate transfer chamber 1027 and the sample transfer/temporary storage chamber 1025 are evacuated using the turbo pump 1013 and the scroll pump 1016. The vacuum at this time was set to 3×10 ⁻⁵ Pa or less as read by the vacuum gauge 1063.
Thereafter, the gate valves 1012, 1024, 1026 and the valve 1014 were closed, and the valves 1022, 1019, 1061 were opened to perform the above-mentioned hydrogen termination treatment. During this treatment, the valves 1072 and 1026 were opened, and the sample transfer/temporary storage chamber 1025 and the transfer intermediate chamber 1027 were evacuated to a vacuum using the turbo exhaust set 1075.

After the hydrogen termination treatment was completed, the valves 1022 and 1019 were closed, the gate valve 1012 and the valve 1014 were opened, and the hydrogen termination treatment chamber 1011 was evacuated to a vacuum using the turbo pump 1013 and the scroll pump 1016 .
Thereafter, the valve 1072 was closed, and the turbo exhaust set 1075 was shut down. The bellows piping 1074 was removed. The gate valves 1024 and 1026 were opened, and the sample was moved to the sample transfer/temporary storage chamber 1025 using the sample transfer rod 1029. When the transfer was completed, the gate valve 1026 was closed.
Thereafter, the gate valve 1012 was closed, and the valve 1022 was opened to introduce Ar gas to set the pressure in the hydrogen termination treatment chamber 1011 and the intermediate transfer chamber 1027 to atmospheric pressure, and then the valve 1024 was closed.

Thereafter, the sample transfer unit E2 was separated from the hydrogen termination unit E1 at the connection between the gate valve 1024 and the transfer intermediate chamber 1027, and the sample transfer unit E2 was connected to the bonding unit E3 at the gate valve 1043.
Also, the vacuum exhaust system E4 was connected to the sample transport section E2 at the flange 1028, and the transport intermediate chamber 1027 was evacuated by the turbo pump 1103 and the scroll pump 1105. When the vacuum dropped to 1×10 ⁻³ Pa or less, the gate valve 1026 was opened. After the angle valve 1102 was closed, Ar gas was introduced into the transport intermediate chamber 1027 and the sample transport/temporary storage chamber 1025 via the bellows piping 1111, the valves 1108 and 1110, the chamber 1101, and the bellows piping 1109. Here, the bonding processing chamber (glove box) 1031 to which the bellows piping 1111 is connected is filled with Ar gas in a refined state at atmospheric pressure by the Ar gas cylinder 1052 and the inert gas circulation refiner (Ar gas circulation refiner) 1040.

Thereafter, the gate valve 1043 was opened, and the sample transport rod 1029 was operated to transport the sample to the bonding processing chamber 1031. Then, the gate valve 1043 was closed.
After that, the h-BN was attached as shown below.

5. Attachment of h-BN (hexagonal boron nitride) The sample in which the exposed first main surface of the diamond substrate 31 was hydrogen-terminated in the hydrogen-termination chamber 1011 as described above was transferred to a glove box 1031 filled with Ar gas via a sample transfer and temporary storage chamber 1025 maintained in a vacuum. In this state, the oxygen concentration in the glove box 1031 was 0.6 ppm or less, and the dew point was −79° C. or less.

In a glove box 1031, single crystal h-BN (synthesized in the National Institute for Materials Science) was cleaved by the Scotch tape method. The cleaved h-BN was transferred onto PDMS (Polydimethylsiloxane) attached to an acrylic substrate. Using an optical microscope, the h-BN on the PDMS film was aligned with the channel region of the diamond, and then the h-BN and diamond were bonded together to form an insulating film 33a (FIGS. 9(a) and 12(a)). Here, it took about 2 hours from when the sample was transported to the glove box 1031 until the bonding of the h-BN was completed.
Thereafter, annealing was performed in a glove box using a sequence of heating from 20° C. to 100° C. in 16 minutes, holding at 100° C. for 30 minutes, heating to 200° C. in 20 minutes, holding at 200° C. for 30 minutes, and heating to 300° C. in 20 minutes, holding at 300° C. for 3 hours.

6. Graphite attachment Graphite (Kish graphite, manufactured by CoorsTek) was cleaved by the Scotch tape method in the glove box 1031. The cleaved graphite was transferred onto the PDMS attached to the acrylic substrate. The graphite on the PDMS film was aligned with the channel region of the diamond using an optical microscope, and the graphite was attached onto the h-BN/diamond.
Thereafter, annealing was performed in a glove box 1031. At this time, a sequence was used in which the temperature was increased from 20° C. to 100° C. in 16 minutes and held at 100° C. for 30 minutes, the temperature was increased to 200° C. in 20 minutes and held at 200° C. for 30 minutes, and the temperature was increased to 300° C. in 20 minutes and held at 300° C. for 1 hour.

7. Formation of Gate Electron After removing the sample from the glove box 1031, a Hall bar pattern was written by the above-mentioned electron beam lithography method. Here, PMMA-A6 (manufactured by Microchem) was used as the resist, a 125 kV electron beam lithography system (manufactured by Elionix, ELS-F125) was used for writing, and a mixture of MIBK (methyl isobutyl ketone):IPA=1:3 was used as the developer.
Then, the graphite was dry etched for 3 minutes using a CCP-RIE device except for the region that was to become the gate electrode. The plasma conditions were _N2 flow rate 96 sccm, _CHF3 flow rate 2 sccm, _O2 flow rate 2 sccm, pressure 10 Pa, and RF output 35 W. During this etching, the h-BN was etched partway in the film thickness direction.
Thereafter, the sample was placed in acetone to remove the resist used as an etching mask. After cleaning with IPA, nitrogen was blown to form a gate electrode _34G made of graphite. During this etching, the exposed area of the first main surface of the diamond substrate 31 was oxidized to form an oxygen termination layer 43a (FIGS. 9(b) and 12(b)).

8. Shaping of h-BN After the gate electrode _34G was formed, a resist pattern 52 was formed by the above-mentioned laser lithography (FIG. 9(c), FIG. 12(c)). The resist was a single layer of AZ-5214E.
Then, the h-BN was dry etched for 3 minutes using a CCP-RIE apparatus. The plasma conditions were _N2 flow rate 96 sccm, CHF3 flow rate ₂ sccm, O2 flow rate ₂ sccm, pressure 10 Pa, and RF output 35 W. The sample was then placed in acetone to remove the resist used as an etching mask. During this etching, the oxygen termination layer 43a was further oxidized, and the oxygen termination layer 43a was changed into a densely oxidized oxygen termination layer 43 (FIG. 9(d), FIG. 12(d)).

9. Adhesion of h-BN for Element Isolation Using the above-mentioned bonding technique, h-BN (61) for running the gate electrode wiring _62G from the gate electrode _34G was bonded to the boundary 71 between the oxygen-terminated and hydrogen-terminated regions to prevent electrical contact between the gate electrode wiring _62G from the gate electrode 34G and the hydrogen-terminated channel portion 32 (FIGS. 10(a) and 13(a)).

10. Fabrication of Wiring Using the above-mentioned laser lithography, a resist pattern 53 for forming the gate electrode wiring (62 _G ), the source electrode wiring (62 _S ), the drain electrode wiring (62 _D ) and their respective bonding pads was formed. The resist was a single layer of AZ-5214E.
Thereafter, Ti with a thickness of 10 nm and Au with a thickness of 100 nm were successively evaporated by an electron gun type evaporation device to deposit a conductive film 62a made of Ti and Au (FIG. 10B, FIG. 13B).
Thereafter, the sample was immersed in acetone to perform lift-off, rinsed with IPA, and then dried with nitrogen blow to produce a MIS type semiconductor device 201 in which a gate electrode wiring 62 _G having bonding pads, a source electrode wiring 62 _S, and a drain electrode wiring 62 _D are formed (FIG. 10( c), FIG. 13( c)).
For reference, FIG. 16 shows an optical microscope photograph of the fabricated MIS type semiconductor device 201 taken from above.

<Electrical characteristics>
The electrical characteristics of the FET (field effect transistor) of the MIS type semiconductor device 201 fabricated by the above-mentioned method were examined. Here, the measuring instruments used were a source measure unit B2901A (manufactured by Keysight Technologies), a function generator 33220A (manufactured by Agilent Technologies), amplifiers 1201 and 1211 (manufactured by DL Instruments), and a digital voltmeter 34401A (manufactured by Agilent Technologies). In addition, a Hall effect measurement was performed using a refrigerant-free cooling device (manufactured by Niki Kogei) equipped with a superconducting magnet and the above-mentioned measuring instruments.

The measurement data of the gate voltage and the Hall mobility are shown in Fig. 17, and the measurement data of the gate voltage and the Hall sheet carrier density are shown in Fig. 18. Here, the thickness of the gate insulating film made of h-BN is 23 nm, and the measurement temperature is 300K.
It is confirmed from FIG. 17 that a high Hall mobility exceeding 600 cm ² V ^-1 s ^-1 can be obtained.
Furthermore, FIG. 18 demonstrates that the Hall sheet carrier density increases linearly as a negative voltage is applied to gate electrode _34G , and that a high Hall sheet carrier density exceeding 6× ¹⁰ cm ⁻² can be obtained when a voltage of −10 V is applied to gate electrode _34G .

Figure 19 shows the plot of the relationship between Hall density and Hall mobility based on the data in Figures 17 and 18. The figure also shows the data disclosed in Non-Patent Document 5 (not necessarily data obtained from Hall effect measurements) in the case where the environment was air after hydrogen termination of the exposed surface of the diamond substrate 31 until the insulating film 33a (h-BN) was bonded. In addition, the figure also shows a theoretical curve of the Hall density dependence of Hall mobility due to the effects of acoustic phonons, surface roughness, surface charge impurities, and the sum of these. The calculation method for the theoretical curve is described in detail below.

The relaxation times τ _imp , τ _ac , and τ _r due to scattering due to negative charges on the surface, acoustic phonon scattering, and surface roughness scattering were calculated from the following equations (A1) to (A3), respectively, and the relaxation time τ due to all of these scatterings was calculated from the following equation (A4).
Here, the formulas (A1)-(A4) are based on the formulas (1), (2), (4) and (5) in Non-Patent Document 6, respectively, but unlike Non-Patent Document 6, the calculations were performed for the heavy hole band, the light hole band and the spin-orbit split-off band. In addition, the effective mass was also distinguished between parallel and perpendicular to the surface. As with the sample prepared, the surface of the diamond is considered to be (111). The mobilities of each were calculated from μ _HH =eτ _HH /m _c ^HH* , μ _LH =eτ _LH /m _c ^LH* and μ _SO =eτ _SO /m _c ^SO* .

where is the reduced Planck constant, n _imp ^(2D) is the surface charged impurity concentration, m _c ^* is the effective mass parallel to the surface, m _z ^* is the effective mass perpendicular to the surface, e is the elementary charge, k _F is the Fermi wave vector, ε ₀ is the vacuum dielectric constant, ε _S is the relative dielectric constant of diamond, q is the two-dimensional wave vector, d is the distance from the surface where the surface charged impurity is located, q _TF is the Thomas-Fermi wave number, p _s2D is the two-dimensional Hall gas sheet density, k _B is the Boltzmann constant, ρ is the crystal mass density, u _l is the longitudinal acoustic phonon velocity, T is the temperature, Δ is the root-mean-square surface roughness, L is the transverse relaxation length of the surface roughness, and D _ac is the acoustic deformation potential.

The theoretical curves of the mobility μ and carrier density n shown in Fig. 19 were obtained from the following formulas (A5) and (A6). Here, taking into consideration that the mobility and carrier density were obtained by the Hall effect in a low magnetic field in the experiment, the following formulas for the mobility and carrier density in a low magnetic field were used.
μ = (n _HH μ _HH ² +n _LH μ _LH ² +n _SO μ _SO ² )/(n _HH μ _HH +n _LH μ _LH +n _SO μ _SO )
... (A5)
n = (n _HH μ _HH +n _LH μ _LH +n _SO μ _SO ) ² /(n _HH μ _HH ² +n _LH μ _LH ² +n _SO μ _SO ² )
... (A6)
Here, _nHH , _nLH , and _nSO are the areal carrier densities of holes belonging to the heavy hole band, light hole band, and spin-orbit split-off band, respectively. For a certain total carrier density, how the carriers are distributed among _nHH , _nLH , and _nSO is found by simultaneously solving the Schrödinger equation and the Poisson equation from the following equations (A7)-(A10).

Here, i represents any of the states in the heavy hole band HH, the light hole band LH, and the spin-orbit split-off band SO.
_mz ⁱ is the effective mass perpendicular to the surface ( _mzHH ^* , _mzLH ^* , _mzSO ^* ), m _// ⁱ is the effective mass parallel to the surface ( _mcHH ^* , _mcLH ^* , _mcSO ^* ), eφ(z) is the potential energy, E _n ⁱ is the eigenenergy (the highest energy of the nth subband where i = HH, LH, SO), Ψ _n ⁱ is the wave function perpendicular to the surface corresponding to the eigenenergy E _n ⁱ , E _F is the Fermi level, n _n ⁱ is the planar carrier density of holes filling the nth subband where i = HH, LH, SO, and n _2D is the total hole carrier density.

The parameters used in the calculation are as follows:
Temperature T=300 K
The dielectric constant of diamond is ε _S = 5.7
Density ρ=3515 kgm ^-3
Longitudinal acoustic phonon velocity u _l = 17536 ms ^-1
Deformation potential D _ac =8 eV
Root mean square (RMS) surface roughness Δ=0.25nm
Lateral relaxation length of surface roughness L = 2 nm
Distance from the surface of the negative charge d = 0
Effective mass parallel to the surface m _c ^*
Heavy hole band m _c ^HH* = 0.299 m ₀
Light hole band m _c ^LH* = 0.503 m ₀
Spin-orbit split-off band m _c ^SO* = 0.375m ₀
( _m0 is the rest mass)
Effective mass in the direction perpendicular to the surface m _z ^*
Heavy hole band m _z ^HH* = 0.763 m ₀
Light hole band m _z ^LH* = 0.248 m ₀
Spin-orbit split-off band _mzSO ^* = _0.375m0
Spin-orbit gap energy Δ ^SO = 6 meV
Donor density N _D =1.76×10 ¹⁶ cm ⁻³ (0.1 ppm)

It can be seen from Figure 19 that an FET (MIS type semiconductor device) fabricated using hydrogen-terminated diamond as the semiconductor layer, h-BN as the gate insulating film ³³ , and in an environment of vacuum or atmospheric Ar gas from the formation of the hydrogen-terminated layer until the ^bonding of the h-BN, can achieve a high hole (Hall) mobility of 5 x ¹⁰² cm2 ^{V -1} s ^-1 or more in the hole (Hall) density range of 2 x ¹⁰¹¹ cm-2 to 6 x 1012 cm ^-2 .
This Hall mobility is about twice as high as that of an FET fabricated under air conditions from the formation of the hydrogen-terminated layer to the bonding of the h-BN. It is also significantly higher than the mobility of the diamond FET previously reported (shown in FIG. 19) and the mobility of the surface conduction of hydrogen-terminated diamond exposed to air, as disclosed in Non-Patent Document 5.
In addition, when comparing the simulation results calculated by incorporating the effects of acoustic phonons, surface roughness and surface charge impurities with the experimental results, it can be seen that the experimental results of the FET of the present invention are in good agreement with the theoretical calculation when the surface charge impurities are 5×10 ¹¹ cm ⁻² . From this, the surface charge impurities of the FET of Example 1, which uses hydrogen-terminated diamond as the semiconductor layer of the present invention, h-BN as the gate insulating film 33, and is fabricated in an environment of vacuum and atmospheric Ar gas from the formation of the hydrogen-terminated layer until bonding the h-BN, is considered to be about 5×10 ¹¹ cm ⁻² . Furthermore, when the surface charge impurities are reduced to 1×10 ¹¹ cm ^{−2 ,} it is theoretically calculated that a high mobility of 1×10 ³ cm ² V ⁻¹ s ⁻¹ or more can be obtained in the carrier density region of 2×10 ¹¹ cm −2 to 6 ^{×10 12} cm ⁻² described above.
In the FET of Example 1, in the carrier density region of 10 ¹² to 10 ¹³ cm ^-2 , the mobility is less suppressed by the surface charge present at the interface between the diamond semiconductor layer 22 and the gate insulator layer 23, and the high mobility characteristic of the diamond semiconductor material can be brought out, resulting in a high mobility.

20 shows the drain voltage dependence of the drain current density of the fabricated MIS type semiconductor device 201. Here, the gate length L _G is 8 μm, the gate width L _W is 0.8 μm, and the thickness of the gate insulating film 33 made of h-BN is 23 nm. The measurement temperature was 300 K, and the gate voltage V _G was −10 V. Although slight hysteresis was observed, good FET operation was obtained for the p-type.

Fig. 21 shows the gate voltage V _G dependency of the drain current density when the source-drain voltage V _DS is -10 V. The gate length L _G , gate width L _W , thickness of the gate insulating film 33, and measurement temperature are the same as those in Fig. 20. It is seen from this result that a high ON/OFF ratio of six or more orders of magnitude is obtained, and the drain current density when the gate voltage V _G is 0 V is smaller than 4 x 10 ^-4 mA mm ^-1 . It was confirmed that the fabricated MIS type semiconductor device 201 is a FET with low power consumption.

Fig. 22 shows the dependence of the mutual conductance _gm on the gate voltage _V. In this case, too, the gate length _L , gate width _L , thickness of the gate insulating film 33, source-drain voltage V _, and measurement temperature are the same as those in Fig. 21. It is seen that the fabricated MIS type semiconductor device 201 has good mutual conductance _gm characteristics.

Fig. 23 shows the relationship between gate voltage V _G and drain current I _D . Fig. 24 shows the gate voltage V _G dependency of the square root of the drain current |I _D | ^1/2 plotted based on the measured data. Here, the gate length L _G is 8 μm, the gate width L _W is 0.8 μm, and the thickness of the gate insulating film 33 made of h-BN is 23 nm. The measurement temperature was 300K, and the drain voltage V _D was -10V.
From this result, the threshold voltage V _TH was calculated to be -0.792 V, proving that the MIS type semiconductor device 201 fabricated in Example 1 performs a normally-off operation.

According to the present invention, it is possible to provide a method for manufacturing a MIS type semiconductor device that has high carrier mobility (hole mobility) and low power consumption in standby mode, thereby contributing to energy conservation, by using a diamond semiconductor that has excellent material properties such as pressure resistance and heat resistance.
Therefore, the present invention paves the way for semiconductor devices capable of handling high power, high frequency, and high temperatures, such as logic circuits that can be used in high temperature environments, and power devices such as inverters that can be used in high temperature environments, and is expected to be widely used in industry.

11: Carbon 12: Hydrogen 13: Boron 14: Nitrogen 21: Diamond substrate 22: Diamond semiconductor layer 23: Gate insulator layer (gate insulating film)
23a: insulating film 24: conductive layer (gate electrode)
25: Insulating film 25a: Insulating film 26: Low resistance layer 27: Gate electrode wiring 28: Source electrode and its electrode wiring 29: Drain electrode and its electrode wiring 31: Diamond substrate 32: Hydrogen termination layer 33: Gate insulating film (gate insulator h-BN)
33a: insulating film _34G : gate electrode (graphite)
35: Conductive film 35a: Conductive film 36: Conductive film 36a: Conductive film _37S : Source electrode _37D : Drain electrode 42: Low resistance layer 43: Oxygen termination layer 43a: Oxygen termination layer 51, 52, 53: Resist pattern 61: Insulating film (h-BN for element isolation)
62: Conductive film (electrode wiring)
62a: Conductive film _62G : Gate electrode wiring (bonding pad wiring)
62 _S : Source electrode wiring (bonding pad wiring)
62 _D : Drain electrode wiring (bonding pad wiring)
71: Boundary between oxygen termination and hydrogen termination regions 101: MIS type semiconductor device 201: MIS type semiconductor device 1001: Processing device 1002: Processing device 1011: Hydrogen termination processing chamber 1012: Gate valve 1013: Turbo pump 1014: Valve 1015: Pipe 1016: Scroll pump 1017: Valve 1018: Pipe 1019: Valve 1020: Baratron vacuum gauge 1022: Valve 1023: Process gas 1024: Gate valve 1025: Sample transfer/temporary storage room 1026: Gate valve 1027: Transfer intermediate room 1028: Flange 1029: Sample transfer rod 1031: Bonding processing room (glove box)
1032: Partition door 1034: Pass box 1035: Valve 1036: Piping 1037: Scroll pump 1038: Valve 1039: Pressure gauge 1040: Inert gas circulation refiner (Ar gas circulation refiner)
1041: Valve 1042: Piping 1043: Gate valve 1044: Valve 1045: Piping 1052: Ar gas cylinder 1053: Piping 1054: Valve 1055: Valve 1061: Exhaust rate adjustment valve 1062: Piping 1063: Vacuum gauge 1071: Piping 1072: Valve 1073: Flange 1074: Bellows piping 1075: Turbo exhaust set 1101: Chamber 1102: Angle valve 1103: Turbo pump 1104: Valve 1105: Scroll pump 1106: Valve 1107: Piping 1108: Valve 1109: Bellows piping 1110: Valve 1111: Bellows piping 1112: Vacuum gauge E1: Hydrogen termination processing unit E2: Sample transfer unit E3: Bonding processing unit E4: Vacuum exhaust system

Claims (10)

forming a semiconductor layer having a first major surface comprised of hydrogen-terminated diamond;
forming an insulator layer in contact with at least a portion of the hydrogen-terminated surface of the semiconductor layer;
forming a conductive layer on at least a portion of the insulating layer;
an atmosphere during the period from immediately after forming the semiconductor layer to immediately before forming the insulator layer is any one selected from the group consisting of a vacuum, hydrogen gas, an inert gas, and hydrogen gas to which an inert gas has been added ;
a density of charged impurities present at the interface between the semiconductor layer and the insulator layer being equal to or greater than 0 cm ⁻² and equal to or less than 5×10 ¹¹ cm ⁻² . forming a semiconductor layer having a first major surface comprised of hydrogen-terminated diamond;
forming an insulator layer in contact with at least a portion of the hydrogen-terminated surface of the semiconductor layer;
forming a conductive layer on at least a portion of the insulating layer;
an atmosphere during the period from immediately after forming the semiconductor layer to immediately before forming the insulator layer is any one selected from the group consisting of hydrogen gas, an inert gas, and hydrogen gas to which an inert gas has been added ;
a pressure of the atmosphere is atmospheric pressure . preparing a member having a first main surface on which at least a portion of a semiconductor layer made of diamond is exposed, and at least a portion of the semiconductor layer is hydrogen-terminated ;
forming an insulator layer in contact with at least a portion of the hydrogen-treated portion of the semiconductor layer;
forming a conductive layer over at least a portion of the insulating layer;
the hydrogen-terminated semiconductor layer is placed in an atmosphere selected from the group consisting of vacuum, hydrogen gas, inert gas, and hydrogen gas with an inert gas added thereto, from immediately after the hydrogen-terminated semiconductor layer is formed until immediately before the insulator layer is formed;
a density of charged impurities present at the interface between the semiconductor layer and the insulator layer being equal to or greater than 0 cm ⁻² and equal to or less than 5×10 ¹¹ cm ⁻² . preparing a member having a first main surface on which at least a portion of a semiconductor layer made of diamond is exposed, and at least a portion of the semiconductor layer is hydrogen-terminated ;
forming an insulator layer in contact with at least a portion of the hydrogen-treated portion of the semiconductor layer;
forming a conductive layer over at least a portion of the insulating layer;
the hydrogen-terminated semiconductor layer is placed in an atmosphere selected from the group consisting of hydrogen gas, an inert gas, and hydrogen gas to which an inert gas has been added, during the period from immediately after the hydrogen-terminated semiconductor layer is formed to immediately before the insulator layer is formed;
a pressure of the atmosphere is atmospheric pressure . 5. The method for manufacturing a MIS type semiconductor device according to claim 1, wherein the atmosphere in which the insulator layer is formed is any one selected from the group consisting of vacuum, hydrogen gas, inert gas, and hydrogen gas with an inert gas added thereto . 6. The method for manufacturing a MIS type semiconductor device according to claim 1, wherein said insulating layer is made of boron nitride. 7. The method for manufacturing a MIS type semiconductor device according to claim 1, wherein said insulating layer is made of single crystal boron nitride. 8. The method for manufacturing a MIS type semiconductor device according to claim 1, wherein said insulating layer is made of hexagonal boron nitride (h-BN). 9. The method for manufacturing a MIS type semiconductor device according to claim 1, wherein a density of charged impurities present at the interface between said semiconductor layer and said insulator layer is 0 cm ⁻² or more and 1×10 ¹¹ cm ⁻² or less. 10. The method for manufacturing a MIS type semiconductor device according to claim 1, wherein said inert gas is argon gas.