JPH05201794A - Production for diamond semiconductor - Google Patents

Abstract

PURPOSE:To provide a producing method for a diamond semiconductor able to grow the single crystalline diamond semiconductor with a substrate inexpensive and easy to obtain. CONSTITUTION:In the producing method for the diamond semiconductor by the vapor phase synthesis, after the 1st growth by growing a polycrystalline diamond on the substrate by the vapor phase synthesis, the diamond single crystal grains 12 are separated from the polycrystalline diamond and the 2nd growth by growing the diamond on the growing surface of the diamond single crystal grains in the 1st growth by the vapor phase synthesis while doping impurities totally or partially is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a diamond semiconductor by a vapor phase synthesis method.

[0002]

2. Description of the Related Art In such a diamond semiconductor manufacturing method, a semiconductor single crystal substrate such as a Si single crystal substrate is
High frequency plasma CVD method or microwave plasma C
A method of synthesizing film diamond while doping impurities by a vapor phase synthesis method such as the VD method has been considered.
According to this method, a diamond semiconductor can be synthesized using an inexpensive and easily available substrate.

[0003]

However, the film-like diamond semiconductor synthesized as described above can only obtain a polycrystalline structure due to the difference in the lattice constant of the substrate and the lattice constant of diamond, and the single crystal is obtained. However, it cannot be used for a semiconductor device that is required to meet the requirements, and there is a problem in that its use as a semiconductor is limited. The present invention has been made in view of the above circumstances, and an object thereof is to provide a diamond semiconductor manufacturing method capable of growing a single crystal diamond semiconductor while using an inexpensive and easily available substrate. It is in.

[0004]

The diamond semiconductor manufacturing method of the present invention is based on the vapor phase synthesis method, and the first feature thereof is to grow polycrystalline diamond on a substrate by the vapor phase synthesis method. 1, the diamond single crystal grains are separated from the polycrystalline diamond, and the whole or part of the diamond single crystal grains are grown on the growth surface of the first growth by the vapor phase synthesis method. The point is to perform a second growth in which diamond is grown while doping impurities. A second feature of the present invention limits the embodiment of the first feature, wherein the substrate is Si.
The point is that the polycrystalline diamond is composed of a single crystal on the (100) plane of the substrate.

[0005]

According to the first feature described above, after the polycrystalline diamond is grown on the substrate by the vapor phase synthesis method, the diamond single crystal grains on the substrate are separated from the single crystal substrate by, for example, plasma etching or chemical etching. .. The separated diamond single crystal grains are arranged on the growth surface in the first growth in the direction in which the diamond further grows, and the diamond is grown again by the vapor phase synthesis method. In the growth in the polycrystalline state, it grows in the direction normal to the growth surface, but in the growth in the direction parallel to the growth surface, the diamond single crystal grains in the polycrystalline diamond collide with each other and grow. Although they interfere with each other, by separating the diamond single crystal grains as described above, the obstacle can be eliminated, and while utilizing the growth surface in the polycrystalline state in the first growth, By the growth, not only the height of the crystal in the direction normal to the growth surface can be increased, but also the area of the growth surface can be increased, and a large-sized single crystal diamond can be obtained. In the second growth, impurities that form acceptors or donors in the diamond single crystal can be doped with good controllability because of the vapor phase synthesis method, and the p-type diamond single crystal or the n-type diamond can be doped. A single crystal is obtained, and the diamond single crystal can be used as a diamond semiconductor. According to the second feature, since the diamond single crystal grains forming the polycrystalline diamond in the first growth grow in an inverted quadrangular pyramid shape, the second growth effectively grows in a direction parallel to the growth surface. be able to.

[0006]

According to the first feature of the present invention, a diamond semiconductor composed of a large-sized single crystal can be synthesized with good controllability while using the above-mentioned inexpensive and easily available substrate. The manufacturing cost of the diamond semiconductor can be reduced as much as possible. Further, according to the second feature, since the shape of the diamond single crystal grains forming the polycrystalline diamond can be made into an inverted quadrangular pyramid shape, the area of the diamond single crystal can be effectively increased, and the second growth can be performed. When arranging the diamond single crystal grains in front of, the concaves are formed on the pedestal to be arranged, and the tip of the quadrangular pyramid is simply inserted into the concaves to form the growth surfaces of the first growth and the second growth. It is possible to combine them and facilitate the work of synthesizing the diamond semiconductor.

[0007]

Embodiments of the present invention will be described with reference to the drawings.
The microwave plasma CVD apparatus shown in FIG. 1 is an apparatus that performs vapor deposition by a microwave plasma CVD method, which is a type of vapor phase synthesis method. Plasma is generated by the energy of microwaves, and material gas is further generated by the plasma. It is a device that dissociates and deposits the dissociated material on a substrate.

In FIG. 1, a substrate support 2 is arranged in a reaction tube 1, and a microwave generated by a microwave oscillator 3 and guided by a waveguide 4 is supplied to the vicinity of the substrate support 2. To be done. Further, in the reaction tube 1, a gas cylinder 5,
Methane gas which is a material gas, hydrogen gas and argon gas which generate plasma are supplied from 6 and 7, respectively, and further, B ₂ H ₆ gas (diborane) and n type which are p-type impurity gases are supplied from the gas cylinders 16 and 17. PH ₃ gas (phosphine), which is an impurity gas, is supplied, and the inside of the reaction tube 1 is exhausted from the exhaust port 8 by the vacuum pump 9.

A process of manufacturing a diamond semiconductor by the above microwave plasma CVD apparatus will be described below. First, the Si single crystal substrate 10 as a substrate is
The reaction tube 1 is placed on the substrate support 2 so that the (00) surface becomes the growth surface, and the inside of the reaction tube 1 is evacuated by the vacuum pump 9. Thereafter, methane gas and hydrogen gas are introduced into the reaction tube 1 from the gas cylinders 5 and 6 while mixing the argon gas from the gas cylinder 7 as needed. When the gas pressure in the reaction tube 1 reaches a predetermined value, microwaves of predetermined power are supplied to the reaction tube 1 to generate plasma. Methane gas is dissociated by this plasma and carbon is deposited on the Si single crystal substrate 10 to form a film-like polycrystalline diamond 11 which becomes an aggregate of minute single crystal grains as shown in the sectional view of FIG. Make the first growth. At this time, the Si single crystal substrate 10
Does not require any special heating means because it is heated by microwaves, but if necessary for setting growth conditions, a heater is provided in the substrate support base 2 to provide the Si single crystal substrate 10 May be heated.

Next, the polycrystalline diamond 11 on the Si single crystal substrate 10 is subjected to air plasma etching mainly containing N ₂ to remove graphite and poor quality diamond grains on the surface of the growth substrate. This etching work
An N ₂ gas cylinder and an O ₂ gas cylinder were added to the above microwave plasma CVD apparatus to obtain a microwave plasma CV.
D device may be used, or another device may be used.

Then, the Si single crystal substrate 10 after the etching treatment is dipped in an etchant containing a mixture of hydrofluoric acid and nitric acid to remove the Si single crystal substrate 10 by etching.
As a result, the polycrystalline diamonds 11 grown on the Si single crystal substrate 10 are separated and the diamond single crystal grains 12 are obtained. The shape of the diamond single crystal grains 12 is a quadrangular pyramid whose bottom surface is the growth surface in the first growth as shown in FIG.

Next, the diamond single crystal grains 12 are
As shown in FIG. 3, the prismatic small holes 14 provided in the support base 13
Then, with the growth surface in the first growth, that is, the bottom surface of the quadrangular pyramid facing upward, the tip of the quadrangular pyramid is inserted and placed on the support base 13. The fine holes 14 of the support 13 can be easily formed by a general etching technique, and the etching shape thereof is not only the prismatic shape as described above but also an inverted pyramid shape, a groove shape, etc. It may be determined according to the 12 shapes. The diamond single crystal grains 12 and the support 13 arranged in this way are again subjected to microwave plasma C
The growth material is placed on the substrate support base 2 of the VD apparatus so that the growth material is supplied in the direction of arrow 15 shown in FIG. 3, and the second growth is performed on the diamond single crystal grains in the same manner as the first growth. I do.

By this second growth, the diamond single crystal grains 12 grow not only in the direction normal to the growth surface but also in the direction parallel to the growth surface because there is no factor that hinders the growth. That is, a large grain single crystal diamond can be obtained. Then, when the diamond single crystal grows to a predetermined size, B ₂ H ₆ gas which is a p-type impurity gas or PH ₃ gas which is an n-type impurity gas is supplied from the gas cylinder 16 or the gas cylinder 17 at a predetermined flow rate.
It is introduced into the reaction tube 1 together with the material gas from the gas cylinders 5, 6 and 7 to synthesize a p-type diamond semiconductor or an n-type diamond semiconductor having a predetermined carrier concentration. At this time, by switching from the introduction state of the p-type impurity gas to the introduction state of the n-type impurity gas, as shown in FIG. 4, the p-type layer 18 and the n-type layer 19 are stacked and stacked to form a p-n layer.
Bonds can also be formed.

[Other Embodiments] In the above embodiment, the Si single crystal substrate was used as the single crystal substrate 10, and the (100) plane was used as the growth surface. However, other materials such as sapphire may be used, or other crystal planes may be used. May be used as the growth surface. As the apparatus used for growing diamond, a high frequency plasma CVD apparatus, a hot filament CVD apparatus, a photo CVD apparatus, an ion beam vapor deposition apparatus, or the like may be used in addition to the microwave plasma CVD apparatus of the above embodiment. Further, the material gas may be other hydrocarbon gas than the above methane gas, and the gas for generating plasma may be other inert gas other than the above hydrogen gas and argon gas. Further, the impurity gas may be gasified with Al, Sb, or the like.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a microwave CVD apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a growth cross section of a polycrystalline diamond according to an example of the present invention.

FIG. 3 is a diagram showing the arrangement of diamond single crystal grains according to an example of the present invention.

FIG. 4 is a diagram showing a growth state of a diamond semiconductor according to an example of the present invention.

[Explanation of symbols]

 10 substrate 11 polycrystalline diamond 12 diamond single crystal grain

Claims (2)

[Claims] 1. A method for producing a diamond semiconductor by a vapor phase synthesis method, the method comprising: first growing a polycrystalline diamond (11) on a substrate (10) by the vapor phase synthesis method; The diamond single crystal grains (12) are separated from 11), and the whole or a part of the diamond single crystal grains (12) on the growth surface of the first growth by the vapor phase synthesis method. A method for manufacturing a diamond semiconductor, which comprises performing a second growth for growing diamond while doping. 2. The method for producing a diamond semiconductor according to claim 1, wherein the substrate (10) is made of Si single crystal, and the polycrystalline diamond (11) is synthesized on the (100) plane of the substrate (10).