JPH01308900A - Production of diamond semiconductor - Google Patents

Abstract

PURPOSE:To obtain the subject semiconductor having prescribed resistivity and crystallinity, in high accuracy and yield, by laminating an impurity- containing layer on a diamond crystal and heating the laminate to effect the solid-solid diffusion of the impurities into the diamond crystal. CONSTITUTION:A plasma-generation chamber 4 containing a substrate 5 is evacuated, supplied with H2 gas and a hydrocarbon gas from a reaction gas feeding system 6 and maintained under a prescribed pressure. Microwave generated by a microwave oscillator 7 is introduced through a wave guide 8 into the generation chamber 4 to generate the electrodeless microwave discharge in the chamber 4 to excite the hydrocarbon and effect the vapor growth of a polycrystalline diamond film 1 on the substrate 5. The polycrystalline film 1 is coated with a solvent solution containing impurities 2a such as group IIIb element or group Vb element, dried to form a thin film 2 containing the impurities on the substrate and calcined at 600-1200 deg.C in an atmosphere of N2, O2, etc., to effect the solid-solid diffusion of the impurities 2a into the polycrystalline film 1 and obtain the objective diamond semiconductor 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diamond semiconductor useful for electronic materials and the like.

[Prior Art] Conventionally, diamond crystals doped with impurities containing elements of the MB group or the VB group of the periodic table, so-called diamond semiconductors, have an extremely larger band gap than general semiconductors (5, It is known as an excellent semiconductor in terms of high hole mobility, high electron mobility comparable to that of Si, low specific dielectric constant, and high thermal conductivity.

As methods for producing diamond semiconductors, the following methods (a) to (C) are conventionally known.

(a) High-pressure synthesis method using a metal catalyst (b3 Method of injecting impurity ions into the diamond crystal by bringing the impurity ions into a high energy state and irradiating the impurity ions into the diamond crystal. (c) Substrate When performing vapor phase synthesis of diamond crystals on top,
A method of introducing a gas containing impurities (doping gas) together with the introduction of a raw material gas for diamond crystal [Problem to be solved by the invention] However, the conventional methods (a) to (C) above include the following:
Each of them had issues as described below.

The high-pressure synthesis method (a) requires expensive and large-scale high-pressure equipment, and metal catalysts, nitrogen, etc. are likely to be mixed into the diamond semiconductor.

In the method of implanting ions in (b) above, 20k
Because ions are implanted with high energy of eV or more,
The resulting diamond semiconductor is prone to defects due to radiation damage, and requires expensive equipment for ion implantation.

In the above method (C) of introducing a doping gas, if a substrate other than a diamond substrate is used, the resulting film tends to be amorphous, making it difficult to obtain the desired diamond crystal.

Therefore, the conventional manufacturing method was complicated and expensive, and it was not possible to obtain a diamond semiconductor having a desired specific resistance value and crystallinity with high precision, and the yield was also very low.

The present invention has been made to solve such problems, and its purpose is to solve the above-mentioned conventional methods (a) to (
An object of the present invention is to provide a method for manufacturing a diamond semiconductor that is more advantageous in terms of quality and cost than cl.

[Means for Solving the Problems] As a result of intensive studies to achieve the object, the present inventors found that the method of introducing impurities by solid phase-solid phase diffusion is the most effective method for introducing impurities in the production of diamond semiconductors. As a law,
They found that it is simple and extremely suitable, and have completed the present invention.

The method for manufacturing a diamond semiconductor of the present invention includes a step of introducing an impurity into a diamond crystal, a step of laminating a film containing the impurity on the diamond crystal, and a step of layering a film containing the impurity on the diamond crystal, and removing the impurity by heating. The method is characterized by comprising a step of solid-phase-solid-phase diffusion of from within the film into the diamond crystal.

More specifically, the method of the present invention first includes, for example, FIG.
), an impurity-containing film 2 is laminated on a diamond crystal 1, and then, as shown in FIG. 1(b),
This method includes a step of solid-phase-solid-phase diffusion of the impurity 2a in the film 2 into the diamond crystal 1 to form a diamond semiconductor 3 as shown in FIG. 1(c).

Hereinafter, the manufacturing method of the present invention will be explained in detail.

Diamond crystals used in the method of the present invention include, for example, diamond single crystals, Si, Ta, Mo, Si02
,Aj! These include a diamond polycrystalline film formed by a vapor phase method on a substrate such as No. 203, and a diamond epitaxial film formed by a vapor phase method on a diamond single crystal substrate.

Note that the shape of the diamond crystal used is not limited to a film shape.

Diamond crystal films synthesized by the vapor phase method are usually
It also contains parts that do not have a diamond crystal structure. When using a diamond crystal film containing such portions as a diamond crystal in the method of the present invention,
The present invention has the advantage that the heated portion is removed by heating in the solid phase-solid phase diffusion process of impurities, which will be described in detail later, and only diamond crystals are obtained.

The impurity in the method of the present invention is not particularly limited as long as it is a substance that can be introduced into the diamond crystal and changes its electrical conductivity, for example,
Compounds having IIT b-group elements such as B, Ai, Ga, In, and Tl; for example, compounds having vb-group elements such as N, P%As, Sb, and Bi.

In the method of the present invention, first, a film containing impurities as described above is laminated on a diamond crystal.

One embodiment of the layer forming method includes, for example, a method in which a liquid in which impurities are dispersed is applied onto a diamond crystal, and the coating film is solidified by an appropriate method.

The coating method is not particularly limited as long as it is possible to form a suitably uniform film, and for example, a spin code method can be used.

The dispersion liquid to be applied is not particularly limited as long as it has a suitably good film-forming property, and an appropriate solvent may be used depending on the type of impurity.

Further, in order to maintain the dispersibility of impurities, a suitable organic binder or the like may be added to prepare a dispersion liquid.

For example, when using a boron compound as an impurity, a polymer in which the boron compound is bonded to a molecular chain by reaction can be dissolved in an alcohol-based solvent, and the solution can be applied onto the diamond crystal. Next, the coating film is heated to 600 to 1200 in an atmosphere of N2 gas or 0□ gas.
A B2O3 film is obtained by firing at a temperature of about .degree.

Further, the above-mentioned impurities can be added to a silicon-based compound represented by the structural formula R, Si(○H)4-, to form a dispersion.

Furthermore, the impurities described above can be added to a suitable metal hydroxide colloid, metal acid ester, metal alcoholate, etc. to prepare a dispersion. Examples of metal alcoholates include ethylene silicate and silicon tetraethoxide.

In the method of the present invention, after the above-described film stacking is formed, impurities are solid-phase-solid-phase diffused from within the film into the diamond crystal by heating.

The heating conditions may be set so that the impurities undergo solid phase-solid phase diffusion to obtain a diamond semiconductor exhibiting the desired electrical conductivity. It needs to be set appropriately depending on the desired electrical conductivity of the diamond semiconductor, and is not particularly limited.

Further, the heating may be performed while introducing N2 gas, O2 gas, etc. into the reaction chamber. When the 02 gas is introduced, the organic binder is decomposed into CO2 and N20 and removed from the system, and the oxidation of the BaO2 film can be sufficiently promoted.

Furthermore, by controlling the heating conditions, the diffusion rate and state of impurities can be controlled, and the specific resistance value of the obtained diamond semiconductor can be controlled. In other words, diamond thin films usually contain amorphous or graphite components other than diamond crystals, but
In performing solid-phase diffusion in the present invention, parts other than diamond crystals, such as graphite components, are burned by being heated in the presence of O2, so the specific resistance value can be controlled. Therefore, to give an example, the heating temperature is about the combustion temperature of graphite (600 to 650°C).

After the impurity is diffused as described above and a desired diamond semiconductor is formed, if it is necessary to remove the impurity-containing film, it may be removed.

The removal method is not particularly limited, but it can be removed, for example, by etching. If the film to be removed is a B2O3 film, the film can be easily removed by etching using HF or the like, for example.

By the method of the present invention as explained above, a high quality diamond semiconductor can be manufactured.

That is, as mentioned earlier, diamond semiconductors obtained by the conventional manufacturing method (a) are often contaminated with metal catalysts, nitrogen, etc., and diamond semiconductors obtained by the conventional manufacturing method (b) are often contaminated with metal catalysts, nitrogen, etc. In many cases, defects are caused by radiation damage, and diamond semiconductors obtained by the conventional manufacturing method (c) are often amorphous, but diamond semiconductors manufactured by the method of the present invention do not have such defects. Therefore, it is a high quality semiconductor having desired specific resistance value and crystallinity.

Such diamond semiconductors are very useful as electronic materials such as high-temperature transistors, diodes, light emitting devices, and ultraviolet laser devices.

The manufacturing apparatus that can be used in the method of the present invention may be any apparatus that has means for heating to enable solid-phase diffusion of impurities as described above.

Therefore, the special and expensive equipment required to carry out the conventional manufacturing methods (a) and (b) as described above is
It is not necessary when carrying out the method of the invention.

FIG. 1 is a schematic diagram showing an example of an apparatus that can be used in the method of the present invention.

This apparatus is a microwave plasma CVD apparatus conventionally used for forming diamond thin films and the like.

According to this device, a diamond thin film is first formed by the microwave plasma CVD method, and then the method of the present invention can be performed using that thin film, making it possible to perform continuous steps and simplifying the process. has advantages.

This device includes a means for placing a substrate 5 inside a plasma generation chamber 4, a system 6 for supplying a reactive gas to the plasma generation chamber 4, and a waveguide 8 for introducing microwaves from a microwave oscillator 7. and an exhaust system 9.

When forming a diamond crystal film using this apparatus, first, the pressure inside the plasma generation chamber 4 is reduced, and hydrogen gas, hydrocarbon gas, etc. are introduced through the reaction gas supply system 6 while adjusting the flow rate, and the plasma is generated. The inside of the plasma generation chamber 4 is maintained at a predetermined pressure, and the microwave oscillator 7 generates a microwave nonpolar discharge inside the plasma generation chamber 4. This discharge generates hydrocarbons in an excited state, and a diamond thin film is formed on the substrate 5. can be grown in vapor phase.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 First, using the apparatus shown in FIG. 1, Si was prepared under the following conditions.
A diamond polycrystalline film with a thickness of 4 μm was formed on the substrate. Raw material gas: Co and N2 (Co/CO+H, = 5%) Gas pressure: 50 Torr Substrate temperature: 900°C Microwave: 2.45 GHz Discharge electric crab 550W The fact that the film is a diamond polycrystalline film It was confirmed that the Raman spectrum had a clear peak at 1332 cm''.

Next, a polymer having a structure represented by the following general formula (1) obtained by reacting and bonding a boron compound to an organic polymer and containing 1.4% by weight in terms of B2O3 with respect to the organic polymer ( Manufactured by Tokyo Ohka Kogyo, product name: PBF,
3M-31) in methyl cellosolve solvent,
A polymer solution was obtained.

Next, the polymer solution was applied onto the diamond polycrystalline film using a spinner at a rotation speed of 3000 rpm for 20 seconds.

The coating film was then beta-king in air at a temperature of 60° C. for 30 minutes.

Next, N2 gas and 02 gas were applied to the 3000A thick polymer solution coating at N2:0□=IA:
Solid phase-solid phase diffusion was performed in a diffusion furnace at a temperature of 1000° C. for 30 minutes while introducing at a flow rate of 0.0:l (at normal pressure).

Next, the polymer solution coating film on the diamond polycrystalline film was removed by etching with HF to obtain a diamond semiconductor.

The diamond semiconductor obtained as described above was a p-type semiconductor with a specific resistance of about 5 x 10' Ωcm. Also, the Raman spectrum of this diamond semiconductor is 1
A peak was observed near 332 cm-', confirming that it was a semiconductor having diamond crystals.

Example 2 First, a diamond polycrystalline film was formed in the same manner as in Example 1.

Next, the SiO□ concentration was 6.0% by weight, and the BzOz concentration was 1.0% by weight.
At 0 g/100 mA, 5 iOz, a boron compound (impurity concentration 1 g/100 cc), and a sugar additive for stably retaining B2O3 were dissolved in methyl cellosolve solvent.

Next, the solution was applied onto the diamond polycrystalline film.
The coating was applied using a spinner at a rotation speed of 3000 rpm for 15 seconds.

The coating film was then baked in air at a temperature of 500° C. for 30 minutes.

Next, the inside of the microwave discharge device was heated to 10-'Torr.
After evacuating to
Solid phase-solid phase diffusion was performed for 30 minutes at °C.

Next, the solution coating film on the diamond polycrystalline film was removed by etching with HF to obtain a diamond semiconductor.

The diamond semiconductor obtained as described above was a p-type semiconductor with a specific resistance of about 2xlO'Ωam. Also,
The Raman spectrum of this diamond semiconductor is 133
A peak was observed around 2 cm-', confirming that it was a semiconductor having diamond crystals.

Example 3 First, using the apparatus shown in FIG. 1, a diamond single crystal film having a thickness of about 3 μm was formed on the polished (110) plane of a Guyanmond substrate.

Next, the Si○2 concentration was 6.0% by weight, and the P2O5 concentration was 1.
5i02 and the phosphorus compound were dissolved in ethanol solvent at 0g/100ml.

Next, the solution is applied onto the diamond single crystal film,
The coating was applied using a spinner at a rotation speed of 2000 rpm for 15 seconds.

The coating film was then baked in air at a temperature of 500° C. for 20 minutes.

Next, solid phase-solid phase diffusion was performed on the 15008 mm thick solution coating film under the same conditions as in Example 2.

Next, the solution coating film on the diamond single crystal film was removed by etching with HF to produce a diamond semiconductor.

The diamond semiconductor obtained as described above was an n-type semiconductor with a specific resistance of about 2XlO'Ωcm. Also,
The Raman spectrum of this diamond semiconductor is 133
A peak was observed around 2 cm'', confirming that it was a semiconductor having diamond crystals.

〔Effect of the invention〕

As explained above, in the method of the present invention, films containing impurities are stacked and solid-phase diffused, so that a diamond semiconductor having desired characteristics can be easily manufactured with a high yield.

Furthermore, the method of the present invention can be easily carried out using simple equipment.

[Brief explanation of the drawing]

FIG. 1 (a) to (c) are schematic diagrams schematically showing the steps in the manufacturing method of the present invention. FIG. 2 is a schematic diagram showing an example of an apparatus that can be used in the manufacturing method of the present invention. It is. 1... Diamond crystal 2... Impurity-containing film 2a... Impurity 3...
・Diamond semiconductor 4...Plasma generation chamber 5...
・Substrate 6...Reactive gas supply system 7...
・Microwave oscillator 8... Waveguide 9... Exhaust system patent applicant Canon Corporation

Claims (1)

[Claims] A method for manufacturing a diamond semiconductor that includes a step of introducing an impurity into a diamond crystal, a step of laminating a film containing the impurity on the diamond crystal, and heating the impurity from the film to the diamond crystal. A method for manufacturing a diamond semiconductor, comprising a step of solid phase-solid phase diffusion.