JPH0323295A - Method for synthesizing semiconductor diamond - Google Patents

Abstract

PURPOSE:To synthesize semiconductor diamond having satisfactory crystallinity and superior characteristics by a vapor phase method by using a gaseous mixture of a gaseous carbon-contg. compd. with gaseous hydrogen and a gaseous org. phosphorus or boron compd. as a doping gas. CONSTITUTION:When semiconductor diamond is synthesized by a vapor phase method with microwave plasma, etc., a gaseous carbon-contg. compd. such as methane, acetylene or ethanol is mixed with gaseous hydrogen in 0.001-0.2 molar ratio and further mixed with a doping gas and the resulting gaseous mixture is led to the surface of a substrate kept at 600-1,200 deg.C preferably under 10-100Torr pressure. In the case of a p-type semiconductor, a gaseous org. boron compd. such as B(CH3)3 or BH(CH3)2 is used as the doping gas. In the case of an n-type semiconductor, a gaseous org. phosphorus compd. such as P(CH3)3 or PH(CH3)2 is used.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention relates to a method for synthesizing semiconductor diamond, and in particular to a method for synthesizing semiconductor diamond that exhibits good properties without deterioration of film quality due to doping. , [Conventional technology] Diamond has high hardness, high thermal conductivity, and has excellent insulation properties.
Due to its excellent physical properties, such as being quantitatively and chemically stable, it is expected to be used in a wide range of applications. Among them, diamond has 111 points in particular when used as a semiconductor, such as its large band gap, which allows it to be used at high temperatures, and its high thermal conductivity, which improves the characteristics of elements that generate a large amount of heat. It is believed that this market will develop into a large market in the future. There are three methods for converting diamond into a semiconductor: (1) Doping with boron, nitrogen, etc. in the high-pressure high-knitting synthesis method. (2) Injecting ions such as R elements and scales into the diamond crystal. (3) B2H6 and P113 gases are mixed in the gas phase method. Among these methods, method (1) requires high-pressure equipment and is costly. In addition, there are drawbacks such as contamination of impurities and doping elements not being doped uniformly. Method (2) is also costly because it requires expensive equipment. In addition, since ions are implanted with an energy of several tens of keV or more, there is a drawback that the diamond itself may be damaged. Method (3) was proposed as one that does not have the above drawbacks (for example, Japanese Patent Application Laid-Open No. 59-137
396). Semiconductor diamond can indeed be synthesized using this method, but there is a problem that increasing the doping amount deteriorates the film quality. In addition, with this method, p''R semiconductors can be synthesized relatively easily and have good characteristics, but there is a problem that synthesis of n-type semiconductors is difficult and has poor characteristics. [Problems to be Solved by the Invention J Purpose of the Invention The present invention solves the above problems and provides a method of synthesizing semiconductor diamond with good crystallinity and excellent properties by a vapor phase method. In order to solve the above problems, when a semiconductor diamond is synthesized on a substrate from a mixed gas consisting of a carbon-containing compound gas, hydrogen gas and a doping gas by a gas phase method, an organic boron compound gas or an organic compound gas is used as the doping gas. This provides a method for synthesizing semiconductor diamond characterized by using an isophosphorus compound gas, in which .B ((,f{3)3,BH (CH3
)2, BH2 (CI{a) . B (C
2 Hs ) 3BH (C2 Hs ) 2 .
One or more types selected from BH2 (Cz Hs) are preferable, and as the organic phosphorus compound gas, P(C
H3)3. P}l (CH3) 2. PH2
(CF{3)P (C2H5)2, PH2(C2
H5)3. PH (C2H5)2PF{2(C2
One or more selected from H5) is preferred. [
Effect 1 The effect of the present invention will be explained in more detail. The present invention relates to the synthesis of semiconductor diamond using a vapor phase method. B2 1{6 or P1 as doping gas
When using No. 13 gas, we encountered the phenomenon that film quality deteriorates when the doping amount is increased, and that p-type semiconductors can be synthesized relatively easily, but n-type semiconductors are difficult to synthesize and have poor characteristics. As a result of repeated research into this phenomenon, it was found that when boron and phosphorus are incorporated into diamond, a large amount of hydrogen is also incorporated at the same time, resulting in deterioration of crystallinity and deterioration of properties. In addition, when B2HG is used as a doping gas, B-B bonds originating from undecomposed gas may be incorporated into the film as is, and in this case, efficient or consistent bonding with boron atoms at carbon atom sites may occur. It was discovered that certain substitutions did not occur, resulting in deterioration of crystallinity and properties.
I-{:! We found that when boron is used as a doping gas, phosphorus segregates as the doping concentration increases, resulting in a decrease in crystallinity and properties, similar to the case with boron. This is thought to be due to the formation of P-P bonds in the gas phase and their incorporation into the membrane. Therefore, the doping gas is B(CH3)3 or P(CH3).
By changing to an organic compound such as 3, they discovered that even if the amount of doping was increased to a certain extent, there was no deterioration in crystallinity, and diamond with good properties could be synthesized. This is because the use of these doping gases causes B-B. B-H or P-P.
This is thought to be because it eliminates the bond between P-H and can supply more bonds between B-C or P-C, which are preferable for the synthesis reaction of semiconductor diamond. The present invention was completed based on this knowledge. The present invention will be explained in more detail with reference to Figures 1 and 2 below. FIG. 1 is an explanatory diagram of an example of a diamond synthesis apparatus used when carrying out the present invention using the microwave plasma CVD method. Here, l is carbon-containing compound gas, 2 is hydrogen gas, 3 is doping gas, 4 is a stop valve, 5 is a mass flow controller, 6 is a reaction vessel, 7 is a microwave generator, 8 is a waveguide, and 9 is a 10 is a substrate holder. In FIG. 1, carbon-containing compound gas 1, hydrogen gas 2, and doping gas 3 are mixed and introduced into a reaction vessel 6, with their flow rates being limited by a mass flow controller 5. Microwave plasma is generated in the reaction vessel 6 by operating the microwave generator 7. The base 9 is placed on a base boulder 10 and held in plasma. The carbon-containing compound gas and doping gas are excited and decomposed by the plasma, and semiconductor diamond is produced on the substrate.

FIG. 2 is an explanatory diagram of an example of a diamond synthesis apparatus used when carrying out the present invention using the hot filament CVD method. Here, 1 is a carbon-containing compound gas, 2 is a hydrogen gas, 3 is a doping gas, 4 is a stop valve, 5 is a mass flow controller, 6 is a reaction vessel, 9 is a substrate, and 10 is a substrate holder with a built-in heater. 11 is a raw material supply nozzle;
l2 is thermionic emitting material. 13 is a power supply for heating the thermal lightning tli elbow material, and 14 is a power supply for heating the base holder. In FIG. 2, a carbon-containing compound gas 1, a hydrogen gas 2, and a doping gas 3 are mixed and introduced into a reaction vessel 6 through a raw material supply nozzle 11, with Ml being controlled by a mass flow controller 5. The carbon-containing compound gas and the doping gas are thermally decomposed by the thermionic emitting material (2) heated by the thermionic emitting material heating power source (13), and semiconductor diamond is generated on the substrate 9 heated on the substrate holder (10). In this way, by using an organic compound as a doping gas when synthesizing semi-quadramid diamond, diamond with good properties can be synthesized without deterioration of crystallinity even if the amount of doping is increased to a certain extent. The doping gas used in the present invention is an organic compound when a p-type semiconductor is synthesized. As an organic & 1L compound. B(CHa)a, BH (CH3)
2, BH2 (CH3)13(C214
5.Mir. BH (C 2
H5) 28H2 (C2 H5). B ((
, 387) a13 (C4 Hg) 3, etc., but considering ease of handling and film-forming reaction, B
(CH3) 3. 13H (CH3) 2
BH2 (CH3). B (C2 H5)3B tl
(C2H5)2. B H 2
(C 2 H 5 ) is desirable. On the other hand, when synthesizing an n-type semiconductor, an organic phosphorus compound is used. As an isophosphorus compound, P(CH3)3Pli (C
}{3) 2. PH2 (CH3)P (
C2 Hs I 3. PH (C2 H5) 2
PH2 (C2 Hs). P (C3 87
)3P(C4H5)2, PH2(C2H5)3, etc. are used, but considering ease of handling and pus-forming reaction, P(CH3)3. P.H.
(CH3 1 2PH2 (CH3)
．． P (C2 Hs) 3P H (C2
Hs) 2. P t{ 2 ( C 2
115) is desirable. Note that the resistivity of the ′+ conductor diamond changes depending on the addition of doping gas. The carbon-containing compound gas is not particularly limited as long as it contains carbon. For example, hydrocarbons such as methane, ethane, broban, ethylene, acetylene, methanol,
These include #-containing carbon compounds such as ethanol and acetone carbon oxide, and #A-containing carbon compounds such as carbon tetrachloride and methyl chloride. Among these, methane, acetylene, ethanol, etc. are preferred because they are easy to handle and decompose.

The mixing ratio (volume ratio) of carbon-containing compound gas and hydrogen gas is not particularly limited, but carbon-containing compound/hydrogen = 0.001 to
A range of 0.2 is preferred. o. No film is formed when the ooi groove is not present, and when the value exceeds 0.2, a graphite-like H4 structure appears. The substrate is preferably one that will not be damaged at -E above 600°C, which is the synthesis temperature of diamond. Examples include metals such as molybdenum and tungsten, semiconductors such as silicon, and ceramics such as quartz di-alumina. Also, diamond may be used. The substrate temperature is 600°C to 1200°C. Diamonds do not form at temperatures below 600°C or above 1200°C. The pressure is O. Although it is possible in the range of 1 to 760 Torr, 10 to 100 Torr is preferable in consideration of the film formation rate and film quality. [Example 1 Example 1 A p-type semiconductor diamond was synthesized using a microwave plasma CVD apparatus shown in Fig. 1. Methane IsccM, hydrogen gas 995CCM as carbon-containing compounds,
B(Cf{a)3 is used as a doping gas, and the B/C ratio in a mixed gas of methane, hydrogen, and B(CH3)3 is 1.
00 ppm and used. Silicon was used as the substrate and it was placed on a substrate holder. Pressure is 30 Torr
As r, the microwave generator was activated and the output was adjusted to 300 W to generate microwave plasma in the reaction vessel. When the substrate was placed in plasma and reacted for 3 hours, p-silicon semiconductor diamond with a thickness of 3 μm was obtained. The specific resistance of this film was 10Ω·cm at room temperature.

Example 2 Using an apparatus using the hot filament CVD method shown in Fig. 2, silicon used as a substrate was placed on a substrate holder heated to 900°C, and the thermionic emissive material was heated to 2000°C using a power source for heating the thermionic emissive material. The mixture was heated to 100°C and the above mixed gas was sprayed from the mixed gas supply nozzle. Other conditions are Example 1
The same is true. As a result, a p-type semiconductor diamond with a thickness of 3 um was obtained, and the specific resistance of this film was 10 Ω・c at room temperature.
Example 3 B as the doping gas { (C I-1 3
) The procedure was the same as in Example 1 except that 2 was used. As a result, a p-type semiconductor with a thickness of 3 um was obtained. Is the resistivity of this III room? The resistance was 10Ωcm. Example 4 B(Ct{3)3 and B}I (
A mixture of C H 3 ) 2 at a ratio of 1:1 was used, and the other conditions were the same as in Example 1. The thickness of the joint is 3
A p-type semiconductor of um was obtained. The specific resistance of this film was IOΩcm at room temperature. Example 5 The same procedure as Example 1 was carried out except that P(C}{3)3 was used as the doping gas. As a result, an n-type semiconductor diamond with a thickness of 3 um was obtained, and the resistivity of this film was 10 at room temperature.
It was 4Ω・cm. Example 6 The procedure was the same as that of actual bmfIA2 except that P(Ct-+3)3 was used as the doping gas. As a result, an n-type semiconductor diamond with a thickness of 3 μm was obtained. The specific resistance of this film was 104 Ω·cm at room temperature.

Example 7 P F{ ( C [{ 3 )] as doping gas
The procedure was the same as in Example 1 except that 2 was used. As a result, an n-type semiconductor with a thickness of 3 um was obtained.6 The specific resistance of this film was 104 Ωcm at room temperature.

Example 8 P(CH3)3 and P H (C
A mixture of H 3 ) 2 at a ratio of 1=1 was used, and its 75) was the same as in Example 1. As a result, an n-pear semiconductor with a thickness of 3 am was obtained. The specific resistance of this model was 104 Ωcm at room temperature. Example 9 Example with only the doping gas concentration changed! , 2 and Example 5.6, p-type and n-type semiconductor diamonds were synthesized, respectively, and their characteristic values were measured. As a comparative example, B2H6 was used instead of B(CH3)3, and PH3 was used instead of P(CF{3)3. At this time, there was no difference in characteristic values between the microwave plasma CVD method and the filament CVD method. The measurement results are shown in Table 1.

From Table 1, it can be seen that the present invention allows synthesis of films with good properties without deterioration of film quality during doping. [Advantages of the invention 1] According to the present invention, in a method for synthesizing semiconductor diamond using a vapor phase method, it has become possible to synthesize semiconductor diamond with excellent properties without deterioration of crystallinity due to doping.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an example of an apparatus used when carrying out the present invention by microwave plasma CVD method, and Fig. 2 is an explanatory diagram of an example of an apparatus used when carrying out the present invention by hot filament CVD method. It is. l... Carbon-containing compound 2... Hydrogen gas 3... Doping gas 4... Stop valve 5... Mass flow controller 6... Reaction vessel T... Microwave generator 8... First conductor Wave tube 9...Substrate 0...Substrate holder 1...Mixed gas supply nozzle 2...Thermionic radiation material 3...Power source for heating the thermal lightning radiation material 4...Power source for heating the substrate holder

Claims (1)

[Claims] 1. When a semiconductor diamond is synthesized on a substrate from a mixed gas consisting of a carbon-containing compound gas, hydrogen gas, and a doping gas by a gas phase method, an organic boron compound gas or an organic phosphorus compound gas is used as the doping gas. A method for synthesizing semiconductor diamond characterized by the use of gas. 2. The organic boron compound gas according to claim 1 is B(CH_
3)_3, BH(CH_3)_2, BH_2(CH_3
), B(C_2H_5)_3, BH(C_2H_5)_
2. A method for synthesizing a semiconductor diamond which is one or more selected from BH_2 (C_2H_5). 3. The organic phosphorus compound gas according to claim 1 is P(CH_3)_3, PH(CH_3)_2, PH_2
(CH_3), P(C_2H_5)_3, PH(C_2
H_5)_2, PH_2 (C_2H_5) A method for synthesizing one or more semiconductor diamonds selected from PH_2 (C_2H_5).