JPH0499871A - Synthetic method for cubic carbon nitride - Google Patents

Abstract

PURPOSE:To deposite a c-BN film on a heated substrate by adding hydrogen and inert gas to the gaseous starting material in the process of synthesizing c-BN by vapor-phase chemical vapor deposition and then passing the gaseous starting material in microwave discharge region using no electrode. CONSTITUTION:The vapor deposition chamber 13 is equipped with a device 12 to supply BCl3 gas to the chamber 13, N2 gas supplying device 14, H2 gas supplying device 15, and He gas supplying device 16, and the chamber 13 is surrounded by a microwave cavity 17 connected to a microwave generator 18. On a susceptor 19 in the chamber 13, a substrate comprising a Si wafer is mounted. In this reactor structure, the chamber 13 is evacuated through an evacuating tube 21, to which each of BCl3 gas, N2 gas, H2 gas and He gas is introduced to obtain 2Torr inner pressure of the chamber 13. Then electrodeless discharge is generated with the microwave generator 18 to form a c-BN film on the substrate 20. The substrate 20 is heated to 300-1300 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for synthesizing cubic boron nitride, which is used as a tool material such as a cutting tool or an electronic material such as a heat sink.

[Prior art] Cubic boron nitride (c-BN) has hardness and thermal conductivity second only to diamond, is extremely chemically stable to iron group alloys, and is highly durable for cutting tools, molds, etc. A wide range of applications can be considered, such as application to improving the properties of semiconductor devices, light emitting devices, etc. Generally, various manufacturing methods using plasma are known for manufacturing c-BH.

Conventionally, Japanese Unexamined Patent Publication No. 62-280365 discloses a method of adding hydrogen to raw material gas. This is done by using boron trichloride, nitrogen 43 and hydrogen as raw material gases and heating the substrate temperature to 300-1500'C.
This is a synthesis method in which the amount of hydrogen gas in the raw material gas is in the range of 0.01 to (1,999) in terms of volume ratio.

Further, Japanese Patent Application Laid-Open No. 63-134661 discloses a method of adding an inert gas to a raw material gas.

The reaction apparatus used in this method is as shown in FIG. 4, where 1 is a boron atom-containing gas supply device that supplies the gas into the chamber 2.

Further, separately from this gas supply device 1, a nitrogen atom-containing gas supply device 3 that supplies a nitrogen atom-containing gas into the chamber 2, and an inert gas supply device 4 that supplies an inert gas are provided. .

A microwave cavity 5 is installed around the outer periphery of the chamber 2, and this microwave cavity 5 is connected to a microwave oscillator 6.

On the other hand, a susceptor 7 is installed in the chamber 2, and a substrate 8 is placed on the susceptor 7. Further, an exhaust device 9 for evacuating the chamber 2 is connected to the chamber 2 . 1o is an exhaust port provided in the exhaust device 9. 11 indicates a valve.

According to this reactor, each gas supply device 1, 3 and 4
A boron atom-containing gas, a nitrogen atom-containing gas, and an inert gas are introduced into the chamber 2 and passed through a microwave electrodeless discharge, and then the substrate 8 is heated to 300 to 1300°C.
c-BN is deposited on the surface. Here, the ratio of the number of boron atoms in the boron atom-containing gas to the number of nitrogen atoms in the nitrogen atom-containing gas is B/N・0.1 to 10, and (number of boron atoms + number of nitrogen atoms)/inert gas The ratio of the number of atoms is in the range of 0.01 to 100.

[Problems to be Solved by the Invention] In the prior art described above, either hydrogen or an inert gas is added to the raw material gas. On a substrate heated to a high temperature, when only the raw material gas is introduced, c-BN
Along with the structure, h-BN (hexagonal boron nitride) and a-BN (
An amorphous boron nitride (boron nitride) structure is also formed. For this reason, a method of adding either hydrogen or an inert gas has been used for the purpose of selectively etching away BN structures other than the c-BN structure.

However, when only an inert gas was added to the raw material gas, it was difficult to generate sufficient c-BN. Furthermore, depending on the selected inert gas, the energy of the excited state may be high and may even damage the film.

On the other hand, when only hydrogen gas is added to the source gas, especially when the excitation method is microwave, the concentration of generated hydrogen atoms is low, making it difficult to obtain a sufficient c-BN structure. In addition, due to the low concentration of hydrogen atoms produced,
There was a problem that the reproducibility of the composition of the formed film was poor.

The present invention was made in view of such conventional problems, and is capable of producing uniform c-BN with good reproducibility (c
- It is an object of the present invention to provide a method for synthesizing BN.

[Means for Solving the Problems] In order to achieve the above object, the invention according to claim 1 uses a boron atom-containing gas and a nitrogen atom-containing gas as raw material gases to produce C-BN by a vapor phase chemical vapor deposition method. c- to synthesize
In the method for synthesizing BN, hydrogen and an inert gas are added to the raw material gas, and the gas is passed through a microwave electrodeless discharge to inject c-
It was decided to deposit a BN film.

The invention according to claim 2 provides a c-BN synthesis method in which c-BN is synthesized by a vapor phase chemical vapor deposition method using a boron atom-containing gas and a nitrogen atom-containing gas as raw material gases, in which hydrogen and an inert gas are After passing through a waveless electrode discharge, it was introduced into a chamber together with the raw material gas, and further exposed to microwave or high frequency plasma for 300 minutes.
A c-BN film was deposited on the surface of the substrate heated to -1300°C.

In the present invention, it is preferable to use nitrogen gas as the nitrogen atom-containing gas.

[Function] When hydrogen and an inert gas are simultaneously introduced into the plasma as a raw material gas, hydrogen atoms are generated according to the following formula. ■
The equation shows the excitation of inert gas molecules by plasma, and the equation (2) shows the generation of hydrogen atoms due to the collision of excited inert gas molecules. This process is known as dissociative Penning ionization.

A+e-→ A・・・・・・・・・・・・・■
H2+ A ・→H+ H” + e −+ A
・= =・ ■A; Inert gas molecules A・; Inert gas molecules in an excited state The lifetime of the excited state of inert gas molecules excited by plasma is relatively long (several 5 - m5), so the high-pressure In the case of microwave plasma that is stable in this region, it ionizes very efficiently. That is, hydrogen atoms are efficiently generated. When hydrogen atoms are generated in high concentration, h due to hydrogen atoms
The selective etching effect of -BN and a-BN works more advantageously, making it possible to produce a c-BN film with a desired composition on the substrate. Here, since an inert gas is also added, h due to excited molecules and ions of the inert gas itself
-BN and a-BN selective etching effects can also be expected.

Furthermore, when nitrogen is used as the nitrogen atom-containing raw material gas, the same etching effect as described above can be expected.

Nz+A・-Nz"+e-+A ・・・・・・・・・
・・・・■N 2 + e−→N2・ ・
・・・・・・・・・・・・■H2+ N 2 ・→H+
H" + 6- + N 2 =...-■N 2
+N2・→N 2 + e −+ N 2 ・・・・
......■Excitation, dissociation, and ionization as shown in the above equation can be considered as molecular processes of nitrogen. ■Equation represents the generation of nitrogen molecule ions through collisions of inert gas molecules in an excited state, ■Equation represents the excitation of nitrogen molecules by plasma, Equation 0 represents the generation of hydrogen atoms through collisions of excited nitrogen molecules, ■Equation show the production of nitrogen molecule ions due to collisions of excited nitrogen molecules. Therefore, hydrogen atoms (H) and nitrogen molecule ions (N2'') are generated from these processes.

Molecular nitrogen ions, like hydrogen atoms, are known to result in selective etching of the h-BN and a-BN structures involved in c-BN formation. Therefore, selecting nitrogen gas as the raw material gas also makes c-BN production advantageous.

[Example] (First Example) Figure 1 shows the reaction apparatus used in this example.
2 is B C10, a gas supply device, and chamber 1
This is to supply B cg 3 gas into the chamber. Also,
Separately from this B Cff 3 gas supply device 12, there is an N2 gas supply device 14 that supplies N2 gas into the chamber 13.
, a N2 gas supply device 15 that supplies N2 gas, and a He gas introduction device 16 that supplies He gas. A microwave cavity 17 is installed around the outer periphery of the chamber 13, and this microwave cavity 17 is connected to a microwave oscillator 18. On the other hand, chamber 13
A susceptor 19 is installed inside the susceptor 1.
A substrate 20 made of an S1 wafer is placed on top of the substrate 9 . Reference numeral 21 indicates an exhaust pipe.

With the reactor having such a configuration, the pressure inside the chamber 13 is reduced through the exhaust pipe 21, and then BCf2.3 gas,
N2 gas, N2 gas, and He gas at flow rates of 1 cc/min, 10 cc/mjn, and 20 cc, respectively.
/min and 50 cc/min, and the pressure inside the chamber 13 was set to 2 Torr. And 245
Electrodeless discharge is generated by a 0MHz microwave oscillator 18, and a 2 μm thick carbon is applied to the surface of the substrate 20 in 2 hours.
- A BN film was formed. Note that the temperature of the substrate 20 is 900°C.
And so.

When this c-BN film was examined by FT-IR (Fourier transform infrared absorption spectrum), it showed remarkable absorption at 105105O', confirming the formation of a c-BN film.

(Second Example) FIG. 2 shows a reaction apparatus used in this example. Components similar to those of the apparatus shown in FIG. 1 are designated by the same reference numerals, and their explanation will be omitted.

In FIG. 2, 22 is an Ar gas supply device that supplies Ar gas into the chamber 13. In addition, 23 is a substrate 20
This is a high-frequency coil that surrounds the

Using the reaction apparatus shown in FIG. 2, the pressure inside the chamber 13 was reduced through the exhaust pipe 21. Then, N2 gas and Ar gas, which are assist gases, are supplied at 10 cc/min and 3
The mixture was mixed at a flow rate of Q Cc/min, and an electrodeless discharge was generated using a 2450 MHz microwave oscillator 18 provided in front of the chamber 13. In addition, apart from this, B
CJ2, gas and N2 gas at 1cc/mi each
The gas was introduced into the chamber 13 at a flow rate of n and 5 cc/min, and mixed with the assist gas. Furthermore, the substrate 20
The above-mentioned mixed gas was flowed nearby, high-frequency plasma was generated by the high-frequency coil 23, and a c-BN film with a thickness of 1 μm was formed on the surface of the substrate 20 in 2 hours. The pressure inside the chamber 13 was I Torr, and the temperature of the substrate 20 was 950°C.

When this c-BN film was examined by FT-IR, it was found that 1051
05O' was observed, and formation of a c-BN film was confirmed.

(Third Example) FIG. 3 shows a reaction apparatus used in this example. Components similar to those of the apparatus shown in FIG. 1 are designated by the same reference numerals, and their explanation will be omitted.

In FIG. 3, 24 is a B2H gas supply device that supplies 82H6 gas into the chamber 13. Further, 25 is NH that is supplied into the NHaHe gas chamber 13.

This is a gas supply device.

Using the reaction apparatus shown in FIG. 3, the pressure inside the chamber 13 was reduced through the exhaust pipe 21. Then, N2 gas and He gas, which are assist gases, are supplied at 10 cc/min each.
The mixture was mixed at a flow rate of 20 cc/min, and an electrodeless discharge was generated using a 2450 MHz microwave oscillator 18 provided in front of the chamber 13. In addition, apart from this, B, H,
Gas, NH, and gas were introduced into the chamber 13 at flow rates of 3 cc/min and 1 cc/min, respectively, and mixed with the assist gas. Furthermore, the above-mentioned mixed gas was flowed near the substrate 20, microwave plasma was generated by another microwave oscillator 18, and a c-BN film with a thickness of 1 μm was formed on the surface of the substrate 20 in 1 hour. chamber 1
The pressure inside 3 is 1 Torr, and the temperature of the substrate 20 is 920°C.
And so.

When this c-BN film was examined by FT-IR, it was found that 105
Remarkable absorption was observed at 105O', confirming the formation of a c-BN film.

[Effects of the Invention] As described above, according to the c-BN synthesis method of the present invention,
Since hydrogen gas and inert gas were added to the source gas, a uniform c-BN film could be synthesized with good reproducibility.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are the first and second embodiments of the present invention, respectively.
A schematic diagram of the reactor used in the second and third examples,
FIG. 4 is a schematic diagram of a reaction apparatus used in a conventional synthesis method. 12...BCρ3 gas supply device 13...
・Chamber 14...N2 gas supply device 15...N2 gas supply device 16...He gas supply device 17...Microwave cavity 8...・・・
Microwave oscillator 0...Substrate 2...Ar gas supply device 3...High frequency coil 4...B2H6 gas supply device 5...NH3 gas supply device

Claims (3)

[Claims] (1) A method for synthesizing cubic boron nitride in which cubic boron nitride is synthesized by a vapor phase chemical vapor deposition method using a boron atom-containing gas and a nitrogen atom-containing gas as raw material gases, in which hydrogen and an inert gas are added to the raw material gases. 1. A method for synthesizing cubic boron nitride, which comprises adding a cubic boron nitride film to a substrate surface heated to 300 to 1300° C. by passing it through a microwave electrodeless discharge. (2) In a method for synthesizing cubic boron nitride by vapor phase chemical vapor deposition using boron atom-containing gas and nitrogen atom-containing gas as raw material gases, hydrogen and inert gas are heated using microwaves without an electrode. After passing through the discharge, it is introduced into a chamber together with the raw material gas, and is further exposed to microwave or high frequency plasma.
A method for synthesizing cubic boron nitride, which comprises depositing a cubic boron nitride film on the surface of a substrate heated to 300°C. (3) The method for synthesizing cubic boron nitride according to claim 1 or 2, characterized in that nitrogen gas is used as the nitrogen atom-containing gas.