JPH0582467B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a vapor-deposited thin film (hereinafter referred to as
The present invention relates to a method and apparatus for forming a thin film that can control the crystallinity, purity, and film composition of the film (simply referred to as "thin film"), and can be adhered to a substrate with excellent adhesion.

<Prior art> As a method of coating a predetermined substrate surface with a thin film,
Conventionally, thin film forming substances have been deposited using vacuum heating evaporation, RF sputter evaporation, ion beam sputter evaporation, ion plating, and chemical vapor deposition (hereinafter referred to as "CVD").
It is known that this can be done by However, these vapor deposition methods have problems with the adhesion between the film and the substrate, tending to cause non-uniformity, peeling, etc., and also make it impossible to control the crystal purity, crystal shape, and film composition of the thin film. There were problems such as.
For example, the deposition of boron nitride films has traditionally been
Although the film was coated on a substrate by the CVD method, the resulting boron nitride thin film had only hexagonal crystals, and it was not possible to form other crystal systems. Moreover, there was a drawback that a large amount of B ₂ O ₃ was mixed into this thin film.

As a way to improve such thin film formation methods, the European academic journal "Japan Journal of Applied Physics" published by the Japan Society of Applied Physics has been published.
In Volume 22 (1983) No. 3 pp171-172,
A paper published by Mamoru Sato and one other person titled “Formation of cubic boron nitride thin film by boron evaporation and nitrogen ion beam bombardment” (English title: Formatio of Cubic
Boron Nitride Films by Boron Evaporation
and Nitrogen Ion Beam Bombardment), while vacuum evaporating boron on the substrate,
It has been reported that a mixed crystal film of hexagonal wurtzite structure and cubic boron nitride can be deposited by irradiation with a kilovolt high-speed ion beam (hereinafter, we will refer to the deposition thin film formation using this method). The method is called the "ion beam irradiation method").

This ion beam irradiation method improves the adhesion of the formed thin film by controlling the current density during ion beam irradiation and the vacuum deposition rate of boron.
Although it has the advantage of being able to control crystal purity and film composition, if the deposited thin film to be formed is an insulating material, the ion beam charge may cause dielectric breakdown.
In the case of semiconductor materials, there are drawbacks such as increased interface state density and damage caused by charged particles.

<Means for Solving the Problems> As a result of various studies to eliminate the drawbacks of conventional vapor-deposited thin film formation methods, the present inventors have developed a thin film conductivity and It is believed that if a high-speed atomic beam, which is unrelated and can affect the constituent atoms of a thin film, is irradiated during the deposition of a deposited film, the crystallinity, film composition, etc. of the deposited film can be controlled according to the irradiation conditions. The present invention was achieved through repeated experiments.

That is, the present invention is characterized in that a thin film-forming substance is deposited on a substrate, and the surface of the deposited film on the substrate is irradiated with a high-speed atomic beam to control the film characteristics of the deposited film.

In the thin film forming method according to the present invention, it is preferable that the high-speed atomic beam irradiated onto the surface of the substrate vapor-deposited film is a high-speed beam that has enough energy to affect the arrangement state and crystallinity of the constituent atoms of the substrate vapor-deposited film, In normal state, atomic beams have too low energy,
High-speed atomic beams accelerated to tens of kiloelectron volts or higher are undesirable because they damage the crystallinity of the deposited film. Furthermore, as for the type of atoms, inert atoms that do not react with the elements constituting the deposited film, such as nitrogen, argon, xenon, helium, and neon, are preferable.

In addition, in order to control the film characteristics of the machine-deposited film, for example, the deposition rate of the thin film-forming substance, the type of atoms of the irradiated high-speed atomic beam, and the excitation conditions (current density, voltage conditions, etc. during atomic beam excitation) must be adjusted. This is done by adjusting one or more of the following:

Further, an apparatus for implementing the thin film forming method according to the present invention includes a thin film forming substrate, a thin film forming substance evaporation source for depositing a thin film forming substance on the thin film forming substrate surface, and a thin film forming substrate surface in a vacuum chamber. The device is characterized by being equipped with a high-speed atomic radiation source that emits accelerated atomic beams.

As a thin film forming substance evaporation source in the thin film forming apparatus according to the present invention, a sputter evaporation apparatus that irradiates a target containing a thin film forming substance with a high speed ion beam or atomic beam in a vacuum chamber to evaporate sputters, and It is preferable to form a vapor deposited film on a thin film forming substrate using a vacuum heating vapor deposition apparatus using heating, high frequency heating, electron beam heating, etc., and irradiating a high speed atomic beam while forming the vapor deposited film.

Furthermore, as a fast atomic radiation source, a certain amount of gas is introduced into a vacuum chamber, and by discharging it with direct current, high frequency, etc., it is turned into plasma, and an electric field is applied to this plasma to accelerate the ions. A high-speed atomic beam is generated by charge exchange collision with gas, etc. In order to focus only the atomic beam on the thin film forming substrate, it is desirable to provide an ion beam deflection voltage or an atomic beam focusing electromagnetic lens in the atomic beam radiation path.

<Function> As described above, the thin film forming method of the present invention deposits a thin film forming substance onto a substrate and irradiates the deposition surface with a high-speed atomic beam. This improves adhesion, controls film composition, improves crystallinity, and prevents dielectric breakdown of thin films.

However, for the sake of simplicity, high-speed nitrogen atoms are formed on the surface of a vapor-deposited film formed by sputtering boron (B) and nitrogen (N) vapor-deposited atoms by irradiating a boron nitride target (hereinafter referred to as "BN target") with ion beam irradiation. Although the formation of a thin film by ray irradiation will be described as a specific example, a thin film is formed by the same mechanism when using other vapor-deposited particles or high-speed atomic beams.

○B Improving adhesion to the substrate At the initial stage of thin film formation, boron 3 and nitrogen vapor deposited atoms 2 sputtered from the BN target undergo reaction due to collision with nitrogen atoms 2a emitted from the high-speed atomic beam for irradiating the substrate. It jumps into the substrate as shown in FIG.

Further, nitrogen atoms themselves are also injected into the substrate 1, and a new mixed phase is formed between the substrate and the deposited boron nitride film. Due to the formation of this mixed phase, the boundary between the substrate 1 and the boron nitride thin film becomes a flash, and as the boundary layer disappears, the adhesion to the substrate becomes stronger.

○B Control over film composition Also, among the boron and nitrogen atoms released from the BN target, the numbers of atoms that reach the substrate are N _T ^B and N _T ^B , respectively. Further, the number of nitrogen atoms emitted from the fast atomic radiation source for irradiating the substrate is assumed to be N _B ^N . Furthermore, if the probability of attachment of boron and nitrogen atoms on the substrate is 1, then the film composition B _X N _y
can be expressed by the following formula.

y/x=N _T ^B +N _B ^N /N _T ^B Therefore, if the number of boron and nitrogen atoms emitted from the BN target is constant (sputtering conditions are constant), the high-speed atomic beam for substrate irradiation is Number of nitrogen atoms emitted from the radiation source N _B ^N
By changing the chemical composition of the boron nitride film deposited on the substrate, it is possible to control the chemical composition of the boron nitride film deposited on the substrate, and it is possible to produce a deposited film in which B:N=1:1.

○C Improving crystallinity Cubic boron nitride is produced under high temperature and high pressure like diamond. If it has an energy of E = 1 (kiloelectrovolt), then this atomic beam is 10 ⁷ (〓) due to the following relationship:
It has an isothermal temperature T of

E=k·T (electron volt) where k represents Boltzmann's constant.

When atoms with such energy are irradiated into a solid, the temperature of the surface layer of the solid is thought to rise locally and rapidly in a short period of time. In addition, atoms in the solid surface layer irradiated with high-speed atomic beams,
As a result, the crystallinity of amorphous boron nitride or hexagonal boron nitride can be improved from amorphous boron nitride or hexagonal boron nitride to cubic boron nitride by simultaneously irradiating high-speed atomic beams during sputter deposition of boron and nitrogen atoms. can.

○D Prevention of dielectric breakdown of thin films due to charge accumulation Since the BN thin film used in this invention is a high resistance film (insulating film) like a diamond thin film, dielectric breakdown will not occur if charges are accumulated in the thin film. It has been reported by Halverson et al. (J.Vac.Sci.Technol.A3 1985 p2141-2146).
In other words, when a BN thin film is irradiated with ions. Cracks occur due to accumulation of surface charge,
While peeling of the film may occur, by neutralizing the charge by irradiating electrons at the same time as ion irradiation, dielectric breakdown of the film is prevented and a smooth, uniform thin film with good adhesion can be formed. However, it is practically difficult to maintain a balance by equalizing the amount of ions and electrons irradiated onto a thin film. On the other hand, unlike ions, high-speed atomic beams consist of particles that have no charge. Therefore, since the device of the present invention can irradiate high-speed atoms (neutral particles),
It has the same effect as simultaneous ion and electron irradiation, and can form a thin film more stably than neutralization.

<Example> Hereinafter, specific embodiments of the present invention will be described.

FIG. 2 shows a schematic configuration of a thin film forming apparatus used in the thin film forming method of the present invention. This device includes a thin film forming substrate 6, a target 7 made of a thin film forming material, and an ion radiation source 8 for emitting ion beams to the target 7, in a vacuum chamber 4 that is evacuated by a vacuum pump 5. A sputter deposition apparatus 9 and a high-speed atomic beam source 10 for emitting high-speed atomic beams onto the deposition surface of the thin film forming substrate 6 are provided.

The ion radiation source 8 is provided with an anode 8c in a chamber surrounded by a cathode wall 8c and a cathode wall 8b on a mounting flange 8a as shown in FIGS. 3A and 3B in a niche of the vacuum chamber 4. A graphite mesh 8d is provided on the target side wall surface of 8b,
The structure is such that argon gas can be supplied from a gas supply source (not shown) into the cathode wall 8b through an introduction pipe 11.

The fast atomic radiation source 10 is located in the niche at the lower right side of the vacuum chamber 4, as shown in FIG. 4, and has the same structure as the ion radiation source 8 shown in FIGS. 3A and 3B.
It has a structure in which a cathode wall 10b is provided in a, an anode 10c is provided in a chamber surrounded by the cathode wall 10b, and a graftite mesh 10d is provided on the target side wall surface of the cathode wall 10b. And the introduction pipe 13
Through the inlet pipe 13 from a gas supply source (not shown)
The structure is such that atomic gas is supplied into the cathode wall 10b through the cathode wall 10b. This fast atomic beam radiation source 10 is
Because it is a cold cathode type, in addition to high-speed atomic beams, ion beams are also emitted in the high-speed energy rays 16 that are emitted, with the ratio of ion beams being 90% and the remaining approximately 10%.
Since this is only a high-speed nitrogen atomic beam, slits 17, 17 are normally arranged in the radial direction of the atomic beam radiation flow of the grafted eye mesh 10d of the high-speed atomic beam radiation source 10, as shown in FIG. Deflection electrodes 18, 18 are provided between the slits 17, 17, and a voltage is applied to these deflection electrodes 18, 18 to prevent the ion beam from being emitted toward the thin film forming substrate 6 side.

Furthermore, if the fast atomic beam radiation source 10 is of the thermionic emission structure type, the emission ratio of the ion beam and the fast beam can be set to 50% each.

Next, a method for depositing a boron nitride film on the thin film forming substrate 6 using the above-described apparatus will be described.

First, the vacuum evacuation pump 5 is operated to create a vacuum in the vacuum chamber 4 of about 1×10 ^-7 to 1×10 ^-8 Torr, and the gas inlet pipe 11 is connected from a gas supply source (not shown).
Argon gas is introduced into the ion radiation source 8 through the ion source 8, and the gas pressure is set to about 10 ^-1 to ^{10 -2} Torr.

Then, the cathode 8b and the anode 8 of the ion radiation source 8
When a high voltage of several tens of volts to several tens of kilovolts is applied between c and a discharge is caused, an argon ion beam 14 is irradiated toward the target 7 through the graphite mesh 8d.

As a result, nitrogen particles and boron particles 15 are sputtered from the surface of the target 7 by the impact of the irradiated argon ion beam, and a vapor deposited film 12 of boron nitride is deposited on the upper surface of the thin film forming substrate 6.

Simultaneously with the operation of the ion beam radiation source 8 described above, nitrogen gas is introduced into the fast atomic beam radiation source 10 from a gas supply source (not shown) through the gas introduction gap 13 on the fast atomic beam radiation source 10 side, and the cathode 10b and anode 1
When a high voltage of several tens of volts to several tens of kilovolts is applied between 0c and a voltage of several tens of kilovolts is applied to generate a discharge, and a voltage is applied between the deflection electrodes 18, 18, the thin film forming substrate 6 is applied across the graftite mesh 10d.
The upper boron nitride vapor deposited film 12 is irradiated with nitrogen atoms, and the adhesion, film composition, and crystallinity between the vapor deposited film 12 and the raised plate 6 can be controlled.

An electron diffraction photograph of the boron nitride vapor deposited film 12 deposited on the substrate 6 by the above method is shown in FIG.
The nitrogen atoms emitted from the fast atomic radiation source 10 had an energy of about 1 kiloelectron volt. ). A clear diffraction pattern is observed in FIG. 5, indicating that the film is a boron nitride film containing a mixture of cubic and hexagonal boron nitride.

On the other hand, the conditions for sputter deposition of boron nitride film (BN
Irradiates the target with 3 kiloelectron volts)
FIG. 6 shows an electron diffraction photograph of a thin film obtained in the same manner as described above, but without irradiation with a high-speed atomic beam during boron nitride vapor deposition. From this photograph, it can be seen that only an amorphous boron nitride film is formed, exhibiting a halo pattern.

Furthermore, it is clear from the infrared absorption spectrum curve diagram in FIG. 7 that impurities in the deposited film can be removed by high-speed atomic beam irradiation. Curve a in FIG. 7 is obtained by irradiating the BN target 7 with a high-speed atomic beam energy of approximately 3 kiloelectron volts using the apparatus shown in FIG. 2, and sputtering boron atoms and nitrogen base atoms to coat the deposited film 12. , curve b is curve a
While depositing the substrate 6 in the same manner as above, the gas inlet 1 is
3, _N2 gas is introduced, and the deposited film 12 is irradiated with a fast atomic beam of nitrogen having an energy of about 1 kiloelectron volt from a fast atomic beam source 10.

In curve a in Figure 7, in addition to the absorption spectrum of boron nitride (~4000 cm ^-1 ), the absorption spectrum of B ₂ O ₃ (3400 cm ^-1 , 1200 cm ^-1 ) is observed, indicating that oxygen is mixed into the film as an impurity. I know what you're doing. On the other hand, in curve b, the absorption spectrum of B ₂ O ₃ disappears. That is, it has become clear that B ₂ O ₃ can be decomposed by high-speed atomic beam irradiation to form a film containing only B and N atoms.

Furthermore, high-speed atomic beam irradiation can improve adhesion by forming an interface between the substrate and the deposited film, which is highly effective.

In this example, when boron nitride was vapor-deposited, a sputter vapor deposition method was used, but the film-forming substance may be vapor-deposited by a method such as vacuum heating, high-frequency heating, or electron beam heating. A sputter deposition method using a high-speed atomic beam may also be used.

<Effects of the Invention> As is clear from the above description, according to the thin film forming method of the present invention, surface charge of the deposited film and dielectric breakdown of the insulating material can be prevented by controlling the crystallinity and controlling impurities in the film. It is possible to control removal, film composition, and form a thin film with high adhesion to the substrate.

Furthermore, the thin film formation of the present invention has the advantage that it can be applied to metal films, insulating films, semiconductor films, composite films of these, etc., which were not possible using conventional ion beam irradiation methods.

In particular, it can be applied to the formation of thin films that require high temperature and pressure, such as boron nitride films, and has high mechanical strength.
It can be applied to various mechanical parts including radiation-resistant containers.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining the mechanism of thin film formation by the thin film forming method according to the present invention, FIG. 2 is a schematic configuration diagram of an apparatus used in an embodiment of the thin film forming method according to the present invention, and FIG. A and B are a cross-sectional view of the main part of the ion beam radiation device in the device shown in FIG.
5 is an electron diffraction photograph showing the crystal structure of a boron nitride vapor-deposited thin film formed on a substrate by the thin film forming method according to the present invention, and FIG. 6 is a conventional atomic beam radiation device according to the present invention. An electron diffraction photograph showing the crystal structure of a boron nitride vapor-deposited thin film formed on a substrate by the ion beam irradiation method according to the present invention, and FIG. 7 is an infrared absorption spectrum of a boron nitride vapor-deposited thin film formed on a substrate by the thin film forming method according to the present invention. It is a line diagram. In the drawing, 4 is a vacuum chamber, 6 is a film forming substrate, and 7 is a vacuum chamber.
is the target, 8 is the ion beam radiator, 10
1 is a high-speed atomic beam radiation device, and 12 is a vapor-deposited thin film.

Claims (1)

[Scope of Claims] 1. A thin film characterized by depositing a thin film-forming substance on a substrate and irradiating the deposition surface of the substrate with a high-speed atomic beam to deposit a vapor-deposited film while controlling the film properties of the vapor-deposited film. Formation method. 2. A patent claim characterized in that the film characteristics of the vapor deposited film deposited on the substrate surface are controlled by controlling at least one of the vapor deposition rate of the thin film forming substance, the type of atoms of the irradiated atomic beam, and the radiation conditions. The thin film forming method according to scope 1. 3. A thin film forming substrate, a thin film forming substance evaporation source for evaporating a thin film forming substance onto the surface of the thin film forming substrate, and a high speed atomic beam radiation source emitting accelerated atomic beams onto the thin film forming substrate surface are provided in the vacuum chamber. A thin film forming apparatus characterized by: 4. As a thin film forming substance evaporation source, a sputter evaporation device that applies a high-speed ion beam or atomic beam to a target and evaporates the thin film forming substance onto the surface of the thin film forming substrate or a vacuum heating evaporation device that heats and evaporates the thin film forming substance is provided. A thin film forming apparatus according to claim 3, characterized in that: 5 Gaseous atoms introduced at a constant pressure into a fast atomic beam radiation source are turned into plasma, which is accelerated by applying a constant electric field, and an ion beam deflector is provided in the radiation direction of the accelerated atomic beam. A thin film forming apparatus according to claim 4.