JPH0745706B2 - Method for forming titanium nitride thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention utilizes an ion beam on the surface of a metal material or an organic material used for tools and various devices used in the metal industry, machinery, equipment industry, etc. The present invention relates to a method for forming a thin film to improve surface performance (hardness, abrasion resistance, heat resistance, corrosion resistance, etc.).

[Conventional technology]

An example of a conventional apparatus for forming a compound thin film by an ion mixing method using an ion beam will be described with reference to FIG. In FIG. 5, (1) is a film forming chamber, (2) is a substrate, (3) is a metal evaporation source (for example, by electron beam heating), (4) is an evaporated metal beam, (5) is an ion beam source, (6) is an accelerated high-energy ion beam, (7) is a substrate holder provided with a heater for heating the substrate, (8) is a vacuum pump, and (9) is a metal to be evaporated.

In the above apparatus, the film forming chamber (1) evacuated to high vacuum
Among them, the metal beam evaporated from the metal evaporation source of (3) (4), for example, the beam of titanium (Ti), and the energy generated from the ion beam source of (5) 10 keV to several 100 keV
For example, nitrogen ion beam (▲ N ⁺ ₂ ▼ and / or N ⁺ )
By irradiating (6) and (6) with a substrate (2) made of steel or the like at the same time, titanium nitride (Ti
The conventional ion mixing method is to form a thin film of N).

[Problems to be Solved by the Invention]

In the conventional method, one component (eg Ti) of the compound (TiN in the above example) is supplied from the evaporated metal beam (4) and the other component (eg N) is supplied from the ion beam (▲ N ⁺ ₂ ▼ and / or Or N ⁺ )
Although the compound film is formed by supplying from (6), since the ion beam incidence frequency on the substrate is generally lower than the metal beam incidence frequency, the compound film formation rate is determined by the ion beam incidence frequency. Film formation was difficult. In addition, since a large current density is required to increase the incidence frequency of the ion beam, it becomes expensive and there is a problem in terms of economy. Further, there is a problem that the hardness of the compound film formed, for example, the titanium nitride film is not constant.

The present invention has been made in view of the above problems, using a nitrogen ion beam of low current density, by an ion mixing method,
It is an object of the present invention to provide a method for forming a titanium nitride thin film at a high film forming rate, and further a method for forming a titanium nitride thin film having high hardness.

[Means for Solving the Problems]

The above-mentioned object is to form a titanium nitride thin film on a substrate by ion mixing by vapor-depositing titanium on the substrate in a nitrogen gas atmosphere and simultaneously irradiating it with a nitrogen ion beam. Titanium nitride characterized by adjusting the flow rate of the nitrogen gas to be introduced and the current density of the nitrogen ion beam to be irradiated so that the X-ray diffraction intensity ratio of the titanium thin film is (111) / (200) ≈0.75. And a thin film forming method.

[Work]

According to the present invention, titanium vapor-deposited on a substrate strongly chemisorbs (dissociates) nitrogen gas (N ₂ ) in the atmosphere. In this state, restrained nitrogen ion beam (▲ N ⁺ ₂ ▼ and / or N ⁺ )
When irradiated with nitrogen, some of the nitrogen atoms (N) adsorbed on the titanium surface are sputtered and released from the surface and released into the atmosphere, while the remaining N is mixed by the ion beam (cascade, mixing, acceleration) It is taken into the film by diffusion or the like) to form a titanium nitride (TiN) thin film.
That is, the N component of titanium nitride is supplied from the nitrogen gas in the atmosphere in addition to the ion beam, and the compound film can be formed at high speed by using the nitrogen ion beam having a low current density.

In addition, compared to conventional reactive vapor deposition (for example, a method of evaporating titanium in a nitrogen gas atmosphere),
By irradiating with an ion beam, the film structure changes,
The film characteristics can be changed greatly. That is, a titanium nitride thin film having high hardness can be obtained by adjusting the flow rate of the nitrogen gas to be introduced and the current density of the nitrogen ion beam to be irradiated.

〔Example〕

An embodiment will be described with reference to the apparatus of FIG. 1 for carrying out the present invention.

A flow rate of 7SCCM (standard cubic centimeterper minute) was applied by a mass flow controller (18) into the film formation chamber (11) which was evacuated to _a high vacuum (10 ^-5 Pa) by a vacuum pump (22).
The adjustment nitrogen gas (N ₂₎ (20) to introduce the nozzle (19), keeping the vacuum degree in the reaction chamber to 1.7 × 10 ^-3 P _a by adjusting the opening degree of the pressure regulating valve (21) . Substrate holder (13)
Substrates made of silicon wafer (1
2) was heated and kept at 200 ° C. In this state, the titanium (23) of the metal evaporation source (14) was heated with an electron beam to evaporate the neutral beam (15) of titanium and irradiate the substrate (12).
The deposition rate of titanium is 10Å / sec. At the same time, a nitrogen ion beam (▲ N ⁺ ₂ ▼ and / or N ⁺ ) (17) was generated from the ion accelerator (16) and irradiated onto the substrate (12). The energy of the nitrogen ion beam (17) was 40 keV, and the current density was 5 μA / cm ² .

With the above operation, the thickness of the film formed on the substrate (12) is 1.
It continued until it became 5 μm. The obtained film was densified microcrystalline titanium nitride (TiN).
The intensity ratio of (11) and (200) was close to that of non-oriented (111) / (200) = 0.75. When the hardness of this film was measured, it was a Vickers hardness of 2300 Kgf / mm ² .

Various conditions can be used for carrying out the present invention, in addition to the conditions shown in the above-described embodiments. FIG. 2 shows how the crystal structure of the produced titanium nitride (TiN) film changes as the current density of the nitrogen ion beam changes. The X-ray diffraction intensity ratio (111) / (200) of the crystal plane is taken as an indication of the change in crystal structure. The conditions for film formation are
Substrate temperature: 200 ℃, nitrogen ion beam energy: 40k
eV, titanium deposition rate: 10 Å / sec, nitrogen gas flow rate is 7 SCCM
And 10 SCCM. At this time, the pressure in the film forming chamber (11) was 1.7 × 10 ⁻³ Pa and 2.6 × 10 ⁻³ Pa, respectively. In FIG. 2, when the current density of the nitrogen ion beam is 0, it corresponds to reactive vapor deposition (a method of evaporating titanium in a nitrogen gas atmosphere), but as the current density of the nitrogen ion beam increases as compared to that case. , You can see that the crystal structure is changing. FIG. 3 shows the relationship between the change in crystal structure of the TiN film and the change in hardness (Vickers hardness). The temperature of the substrate (12) has been tested for two types, 40 ° C and 200 ° C. In both cases, (111) / (200)
The hardness of the film is high when it is close to the non-oriented crystal structure of 0.75, and the Vickers hardness is 2000 Kgf / mm ² or more.
An iN film was obtained. The change in the film structure can be seen by observing the film cross-sectional structure with a scanning electron microscope.

It was also observed that the TiN film became dense with the irradiation of the nitrogen ion beam.

Next, FIG. 4 shows the results of measuring the hardness of the TiN film obtained by changing the conditions of the nitrogen gas flow rate and the current density of the nitrogen ion beam. The deposition rate of titanium is 10Å / sec, and the energy of nitrogen ion beam is 40 keV. Although the experimental results vary depending on the temperature of the substrate, it is clear that the hardness of the compound film obtained by flowing the nitrogen gas increases in any case.

As shown in FIG. 2, the titanium deposition rate 10
The current density of the nitrogen ion beam used to obtain Å / sec was less than 30 μA / cm ² . Literature on conventional ion mixing methods (M.Kiuchi, et.al., Japanese Journal of
Applied Physics vol.26, No.6, (1987), pp.L938-L94
According to (0), the current density of the nitrogen ion beam used to obtain the titanium deposition rate of 6.8-7.8Å / sec is 100-300μ.
It is A / cm ² . By the method according to the present invention, it is found that a titanium nitride (TiN) film having a high ion beam hardness, which is as small as about 1/10 of that of the above document, is obtained.

Therefore, according to the method of the present invention, when the same amount of ion beam is used, it is possible to form a film five times or more faster than in the case of the conventional ion mixing method. By adjusting the flow rate of the nitrogen gas introduced at this time and the current density of the nitrogen ion beam to be irradiated, the X-ray diffraction intensity ratio (111) / (200) ≈0.75 of the titanium nitride thin film to be formed is obtained. A titanium nitride thin film having a Vickers hardness of 2000 Kgf / mm ² or more can be obtained.

Although the embodiments of the present invention have been described above, needless to say, the present invention is not limited to these, and various modifications can be made based on the technical idea of the present invention.

For example, in the above embodiment, nitrogen gas, nitrogen ion beam,
An example in which a titanium nitride compound film is formed using a titanium neutral beam has been shown, but various combinations of these are conceivable. In this case, what is important is that the reaction gas used as the atmosphere gas must be strongly chemically (dissociated) adsorbed to the metal film. Many refractory metals (Ti, Ta, M
(O, Nb, Zr, V, etc.) chemically (dissociate) adsorb gases such as N ₂ , NH ₃ , C ₂ H ₂ , and O ₂ , so that these refractory metals are vapor-deposited in these gas atmospheres. And at the same time ▲ N ⁺ ₂ ▼
(And / or N ⁺ ), C ⁺ , O ₂ (and or O ⁺ ) ion beams are irradiated, and these nitrides, carbides, oxides, or compounds composed of a plurality of these, that is, complex compounds, are accelerated. It is possible to form. The reaction gas may be another gas that separates N, C, or O as long as it is strongly chemically (dissociatively) adsorbed to the metal film.

〔The invention's effect〕

Since the present invention is configured as described above, it has the following effects.

That is, the present invention is a method of vapor-depositing titanium in a nitrogen gas atmosphere and simultaneously irradiating a nitrogen ion beam to form a titanium nitride thin film on a substrate, wherein the nitrogen gas strongly adheres to the vapor-deposited titanium film on the substrate. The adsorbed nitrogen atoms are also taken into the film by chemical (dissociative) adsorption, and the ion mixing action of the nitrogen ion beam simultaneously irradiated in that state also forms titanium nitride. Therefore, according to the present invention, since the nitrogen component of titanium nitride is supplied not only from the irradiated nitrogen ion beam but also from the nitrogen gas as the atmospheric gas, the current density of the ion beam can be reduced. The titanium nitride thin film can be formed at a low cost and at a high film forming rate. Further, at this time, the X-ray diffraction intensity ratio (111) / (200) ≈ 0 of the titanium nitride thin film formed.
The Vickers hardness is adjusted by adjusting the flow rate of the nitrogen gas to be introduced and the current density of the nitrogen ion beam to be irradiated so that it becomes 75.
It is possible to obtain a titanium nitride thin film of 2000 Kgf / mm ² or more.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention, and FIG. 2 is a view showing a relationship between a crystal structure of a titanium nitride film obtained by the present invention and a current density of a nitrogen ion beam, FIG. Is a diagram showing the relationship between the crystal structure of the obtained titanium nitride film and its hardness, and FIG. 4 is a diagram showing the relationship between the nitrogen gas flow rate, the current density of the nitrogen ion beam, and the hardness of the obtained titanium nitride film. FIG. 5 is a schematic sectional view showing an example of an apparatus used in a conventional ion mixing method. In the figure, (12) …… Substrate (15) …… Titanium neutral beam (17) …… Nitrogen ion beam (20) …… Nitrogen gas

Claims (2)

[Claims] 1. When forming a titanium nitride thin film on a substrate by an ion mixing method, titanium is vapor-deposited on the substrate in a nitrogen gas atmosphere, and at the same time, a nitrogen ion beam is irradiated to form a titanium nitride film. A titanium nitride thin film, characterized in that the flow rate of the nitrogen gas to be introduced and the current density of the nitrogen ion beam to be irradiated are adjusted so that the X-ray diffraction intensity ratio of the thin film becomes (111) / (200) ≈0.75. Forming method. 2. The method for forming a titanium nitride thin film according to claim 1, wherein the titanium nitride thin film to be formed has a Vickers hardness of 2000 Kgf / mm ² or more.