JPH0735582B2 - Boron nitride formation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a boron nitride forming method for forming boron nitride on a substrate by using ions.

[Conventional technology]

Conventionally, as a thin film forming method, there is a method generally called a CVD method, which is a method of forming a thin film mainly by utilizing a chemical reaction in a high temperature space (including a substrate) or an activated space. is there.

Specifically, for example, a mixed gas of diborane (B ₂ H ₆ ), ammonia (NH ₃ ) and hydrogen (H ₂ ) is used to produce boron nitride (B 2
As for the case of forming N), there is a high frequency plasma CVD method shown in the journal of Precision Engineering (53/10/1987) as an example, which will be described with reference to FIG. In the figure, a heater (33) is arranged on the outer circumference of a quartz reaction tube (32) housed in a vacuum chamber (31), and a substrate (34) is set in the quartz reaction tube (32). A hot cathode (filament) (35) is arranged above the substrate (34). Quartz reaction tube (3
A reactive gas introduction pipe (36) is connected to 2), and a high frequency power supply (38) is connected to a high frequency coil (37) surrounding the quartz reaction pipe (32). (39) is a rotary pump.

When actually operating the high-frequency plasma CVD apparatus having such a structure, first, the rotary pump (39) is operated to adjust the flow rate of the gas introduced from the reactive gas introduction pipe (36), and the quartz reaction pipe In (32), for example, B
While introducing a reactive gas such as ₂ H ₆ , NH ₃ and H ₂ , the pressure inside the quartz reaction tube (32) is reduced to about 0.1 to 10 Torr.

The introduced reactive gas is turned into plasma by the input to the high frequency coil (37) by the high frequency power supply (38) and further activated by the hot cathode (35). Meanwhile, the heater (33)
Causes the substrate (34) to be heated to a high temperature to decompose, reduce or replace the reactive gas on the substrate (B ₂ H ₆ +2
NH ₃ → 2BN + 3H ₂ ) is performed, and the resulting boron nitride (BN) is deposited on the substrate to form a thin film.

[Problems to be Solved by the Invention]

The conventional method for forming boron nitride using a CVD apparatus has the above-described structure, and therefore involves a thin film formation process by a chemical reaction in a high-temperature atmosphere, so that a thin film cannot be formed by a low-temperature process. There was a point.

Further, since the parameters for controlling the film quality are only the gas pressure and the substrate temperature, it is difficult to form a high-performance thin film.

The present invention has been made to solve the above problems, and a method for forming boron nitride by using an ion source capable of forming a high quality thin film having strong adhesion to a substrate by a low temperature process. Aim to get.

[Means for Solving the Problems]

The method for forming boron nitride according to the present invention belongs to an ion beam method, in which a gas containing a boron element and a gas containing a nitrogen element are introduced into an ion source, and the gas is irradiated with an electron beam to excite the gas. , Dissociation and partial ionization, and the ions are accelerated by an electric field to irradiate the substrate.

[Action]

In the present invention, by irradiating the gas or vapor ejected in the shield plate with an electron beam, the gas or vapor such as diborane (B ₂ H ₆ ) or nitrogen (N ₂ ) is excited, dissociated or partially. An ion source is used that is ionized and activated to deposit free elements (for example, B, N) or boron nitride (BN) generated by the reaction on a substrate.

This ion source not only can efficiently excite, dissociate, ionize, or react gas or vapor by electron beam irradiation, but can also control the amount of ions generated by electron beam irradiation and further accelerate it. By changing the kinetic energy of the ions by the voltage applied to the electrodes, boron nitride, which has the effect of sputtering the surface of the ions and has a very strong adhesion to the substrate, can be formed by a low temperature process.

Further, by introducing B ₂ H ₆ and N ₂ gas into different ion sources and changing the ion kinetic energy of boron element and nitrogen element incident on the substrate and the incident amount of each ion, the crystallinity of boron nitride, Not only can the film quality such as hardness and thermal conductivity be freely controlled, but the amount of diborane consumed (the amount of exhaust gas) can be reduced by increasing the amount of nitrogen element ions, and boron nitride can be formed efficiently.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows an example of an ion source (20) used for forming boron nitride (13) on the surface of a substrate (12). The ion accelerating means is an extraction electrode (1) and an acceleration electrode (2). Is formed of a pair of aperture electrodes. The electron beam emitting means comprises a hot cathode (filament) (3) provided in the plasma chamber (70), an electric field shield plate (4), and a grid electrode (5), and the whole is surrounded by the shield plate (8). ing. Reference numeral (71) is a magnetic field applying means for rotating the electron beam emitted from the hot cathode in a spiral rotational motion, which is not particularly required. Gas or vapor such as diborane and nitrogen is introduced into the ion source by a gas injection nozzle (6) supported by an insulating ceramic (7). As a power source, an acceleration DC power source (9) for accelerating ions, an ionization for biasing a plasma chamber (70) composed of an electric field shield plate (4) and a grid electrode (5) to a positive potential with respect to a hot cathode (3). There is a power supply (10) and a hot cathode heating power supply (11).

Next, for the formation of boron nitride, a mixed gas of diborane and nitrogen is used to excite, dissociate, and partially ionize the mixed gas, and the surface of the substrate (12) is irradiated with boron ions, nitrogen ions, or the like to form boron nitride ( The case of forming 13) will be described.

First, a reaction containing diborane (B ₂ H ₆ ), nitrogen (N ₂ ) and the like, the flow rate of which is adjusted, in the ion source in the vacuum chamber (14) which is kept in a high vacuum by an exhaust system (not shown). Gas is introduced from a gas injection nozzle (6) insulated by an insulating ceramic (7), and the gas pressure in the vacuum chamber (14) is adjusted to be about 10 ^-5 to 10 ^-3 Torr.

On the other hand, the heating electrode (2), the electric field shield plate (4) and the grid electrode (5) are arranged so that the electron beam is emitted from the hot cathode (3) heated to about 2000 ° C. by the hot cathode heating power source (11). A negative bias voltage is applied by an ionization power source (10) to the plasma chamber (70) constituted by (1).

At this time, the electron beam is emitted into the plasma chamber (70) in a reaction range and collides with gas particles, so that the gas is efficiently excited, dissociated, and ionized. Further, the gas pressure in the ion source is kept higher than that in the vacuum chamber (14) by the shield plate (8), so that the excitation, dissociation and ionization of the gas can be performed more efficiently by the electron beam irradiation. Be seen.

Further, the magnetic field applying means (71) can make the electrons spiral to increase the efficiency.

On the other hand, when a voltage is applied between the extraction electrode (1) and the acceleration electrode (2) by the acceleration power supply (9), the above-mentioned ions are accelerated and kinetic energy is obtained to reach the substrate (12),
Boron nitride (13) is formed by the chemical reaction. The crystallinity of boron nitride (13) formed on the surface of the substrate (12) is changed to cubic (CBN) by changing the acceleration voltage at this time.
Can be changed to hexagonal (hBN) and electrical and mechanical properties can be changed.

As described above, a substrate provided with high-performance boron nitride formed by controlling the physical properties of boron nitride has a wide range of application fields such as a magnetic disk protective film and mechanical wear resistant parts.

Next, another embodiment will be described with reference to FIG. This is a case where boron nitride is formed using a plurality of ion sources (20a) and (20b).
In a) and (6b), for example, diborane (B ₂ H ₆ ) and nitrogen (N ₂ ) or ammonia (NH ₄ ) gas are introduced into the ion source. (70a) and (70b) excite each gas,
A plasma chamber that dissociates or ionizes. (1a),
(1b) and (2a), (2b) are extraction electrodes and acceleration electrodes that apply different accelerating voltages and make boron ions and nitrogen ions respectively enter the substrate (12) forming the boron nitride (13). .

With the above device, for example, diborane (B ₂ H ₆ ) and nitrogen (N ₂ ) gas are introduced into the respective ion sources from the gas injection nozzles (6a) and (6b), and the respective gases are introduced into the plasma chamber (70a). , (70b) are excited, dissociated, and partially ionized, and if different acceleration voltages are applied between the extraction electrodes (1a) and (1b) and the acceleration electrodes (2a) and (2b), they become boron ions. Since the energy of the nitrogen ions incident on the substrate (12) can be controlled independently, the crystallinity, electrical properties, and mechanical properties of the formed boron nitride (13) can be controlled more freely.

Specifically, if the amount of nitrogen ions incident on the substrate (12) and the kinetic energy thereof are made larger than the amount of boron ions incident on the substrate (12), the consumption amount of diborane, that is, it is not used for film formation. The amount exhausted can be reduced.

Also, when film formation is performed while implanting nitrogen ions into the substrate,
Mechanical properties such as hardness can be further improved.

In each of the above embodiments, the case where boron nitride is formed by using diborane and nitrogen is described, but this combination includes diborane and ammonia gas, a gas containing a boron element or a mixed gas containing a boron element and a nitrogen element. Boron nitride can be formed in any combination as long as it is a combination of gas containing or mixed gas containing nitrogen element.

Further, a microwave applying means may be used instead of the hot cathode (filament) (3).

〔The invention's effect〕

As described above, the present invention excites, dissociates, and partially ionizes gas by the ion source provided in the vacuum chamber and accelerates the ions to form boron nitride on the substrate. Boron nitride is obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an apparatus used in an embodiment of the present invention,
FIG. 2 is a vertical sectional view of an apparatus used in another embodiment, and FIG. 3 is a vertical sectional view of a conventional CVD apparatus. (1) …… Extraction electrode, (2) …… Acceleration electrode, (3)
... hot cathode, (4) ... electric field shield plate, (5) ... grid electrode, (6) ... gas injection nozzle, (7) ... insulating ceramic, (8) ... shield plate, (12) …… Substrate, (13) …… Boron nitride, (70) …… Plasma chamber,
(71) …… Magnetic field application means. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A gas containing a boron element and a gas containing a nitrogen element are introduced into an ion source, and the gas is irradiated with an electron beam in the ion source to excite, dissociate and partially ionize the gas. A method for forming boron nitride, wherein ions are accelerated by an electric field to irradiate the substrate to form boron nitride on the substrate.