JPS6270295A - Production of n-type semiconductive diamond film - Google Patents

Abstract

PURPOSE:To enable the production of a diamond film exhibiting N-type semiconductor characteristics, by carrying out the thermal decomposition or plasma decomposition of a dopant gas containing P, As and/or Sb and a reaction gas containing a hydrocarbon and hydrogen at a specific ratio thereby depositing the film on a substrate. CONSTITUTION:A diamond film is synthesized in vapor phase from a mixed gas of hydrocarbon and hydrogen containing P, As and/or Sb as a dopant by the following procedure. A hydrocarbon gas such as CH4, C2H6, etc., and H2 gas are mixed to a dopant-containing gas such as PH3, AsH3, etc., capable of easily releasing an impurity such as P, As, Sb, etc., by decomposition. The molar ratio of C to H2 in the mixed gas is adjusted to 0.001-0.02 and the molar ratio of the dopant element such as P, As, Sb, etc., to C is adjusted to 0.0001-0.002. The hydrocarbon in the mixed gas is thermally decomposed by plasma CVD process or CVD process to obtain a diamond thin film having N-type semiconductor characteristic and usable effectively for electronic device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a diamond film exhibiting n-type semiconductor characteristics used in electronic devices and the like.

[Background of conventional technology]

Carbon (C) belongs to the lVb group in the periodic table, and is thought to have the potential to be used as a semiconductor material like Si, which is in the same group. However, graphite is highly conductive and cannot be used as a semiconductor, whereas diamond is insulating, so it is theoretically possible to use it as a semiconductor by adding impurities or other methods.

Most naturally occurring diamonds have an electrical resistance of 10 Ω.
Although it is an insulator with a value exceeding the
There is a type with a low resistance value, which is called the nb type. 1
Detailed investigation has revealed that this nb-type semiconductor is a p-type semiconductor, which can be artificially produced by ultra-high pressure and high temperature synthesis. However, diamond, which is an n-type semiconductor, not only does not exist naturally, but also there is no example of its production by ultra-high pressure synthesis.

Both p- and n-type semiconductors are essential for the production of diamond semiconductor devices, and to make this possible, attempts have been made to manufacture n-type semiconductors using the 9.9-on method. Ta. As a result, an ion-implanted layer of Sb, ^r, C, etc. and B
It has been reported that the junction with the injection layer has V-■ characteristics close to rectifying action. However, it has not yet been confirmed that it is an n-type semiconductor.

[Disclosure of the invention]

In order to solve the above-mentioned problems, the present invention provides an n-type film using a thin film method.
The present invention provides a method for manufacturing a type semiconductor layer.

A feature of the present invention is that a gas that easily decomposes and releases impurities (dopants) such as P and ^S is introduced during vapor phase synthesis of a diamond film from a mixed gas of hydrocarbons and hydrogen. We believe that when impurities are introduced in this type of vapor phase synthesis, they are contained much more uniformly than in high-pressure synthesis, and the impurity atoms can enter into more reasonable positions than in ion implantation, making it easier to produce the effect as a dopant. The present invention was realized based on this idea, and succeeded in synthesizing an n-type semiconductor that could not be synthesized by conventional high-pressure synthesis methods or ion implantation methods.

In order to carry out the present invention, it is necessary to use a thin film diamond synthesis method, and plasma CVD or CVD is preferable for forming a film with good crystallinity without residual carbon.

In this case, it is appropriate that the reaction gas has a molar ratio of hydrocarbon C to H a of 0.001 or more and 0.02 or less.

If it is less than 0.001, the growth rate of the film will be extremely slow and uneconomical, and if it is more than 0.02, the crystallinity of the film will be poor and it will not be possible to add sufficient performance as a semiconductor layer.

In addition, as dopant elements, P, ^s, and Sb are ordinary S.
This had the same effect as when t was made n-type.

The molar ratio between the dopant element and C is 0.0001 or more and 0.0001 or more.
It should be 002. If it is less than 0.0001, sufficient conductivity as a semiconductor cannot be achieved. Moreover, if it is more than 0.002, strain will occur in the film, resulting in a film with many defects, making it difficult to apply to semiconductor devices.

If the film produced in this way is formed on a diamond single crystal, it can be epitaxially grown to obtain a single crystal film, so that it can be used as a semiconductor element.

Further, as a thin film forming method, either plasma CVD or CVD can be used. As a gas excitation means, any means such as high frequency, microwave, electron beam, laser, etc. will have the same effect, and it is also within the scope of the present invention to further strengthen the excitation using a magnetic field.

Next, a detailed explanation will be given with reference to Examples.Example 1 Using a known plasma CVD method (in which plasma is ignited using 2.45 Gb of microwave), CH 0.5%
, Plh: A 0.5 μ
A diamond film with a thickness of m was formed. The electrical resistance of this film was measured to be 1X10'Ω, and as a result of measuring the Hall effect, it was confirmed that it was an n-type semiconductor.

Example 2 Diamond films each having a thickness of 0.3 μm were prepared using the same method as in Example 1 using the reaction gas having the composition shown in Table 1, and the electrical resistance and electron mobility were measured. The results are shown in the table.

Table 1 Example 3 C/Hz = 0.0 by known CVD (pyrolysis with a tungsten filament heated to about 210 l)
05. CJa+ASHt+H so that A s / C = 0.001! When the gas was mixed and a 0.3 μm film was formed on an artificial diamond single crystal and the electrical resistance and ball effect were measured, the resistance was 1.5 x 10-Ωl and it was identified as n-type, and the electron mobility was 720CII+ /ν,s
It was ec.

Procedural amendment June 1986

Claims (3)

[Claims] (1) A method for producing an n-type semiconductor diamond film, characterized in that a reaction gas consisting of a gas containing a dopant element, a hydrocarbon gas, and hydrogen is thermally decomposed or plasma decomposed and deposited on a substrate. (2) The method for producing an n-type semiconductor diamond film according to claim 1, wherein the dopant element is one or more selected from the group consisting of P, As, or Sb. (3) The molar ratio of carbon atoms to hydrogen molecules in the reaction gas is 0
．． 001 to 0.02, and the molar ratio of dopant atoms to carbon atoms is 0.0001 to 0.002.