JPH062953B2 - Thin film forming equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for forming a thin film using plasma.

Conventional technology High hardness carbon film has characteristics very similar to diamond,
By applying various properties such as high hardness, low friction coefficient, high insulation, high thermal conductivity, and high light transmittance to the product, it is possible to make the product with extremely high added value. Many announcements have been made regarding an apparatus for forming a high hardness carbon film, and they are roughly classified into a PVD apparatus and a CVD apparatus.

Fig. 4 shows an ion beam deposition device that is a typical conventional example of forming a high-hardness carbon film using a PVD device [AISENBERG et al., "JOURNAL OF APPLIED P
HYSICS) "Volume 42 (1971) P. 2953-P. 2958].

The operation of this conventional example will be outlined below. After the vacuum container 31 is evacuated by the vacuum pump 35, argon 33 is introduced into the source chamber 40 to supply 2 × 10 ⁻³ to 50 × 10 ⁻³ To.
Set to rr. On the other hand, at this time, the vacuum container 32 is evacuated by the vacuum pump 39 and set to 10 ⁻⁶ Torr. After this,
A voltage is applied between the carbon electrode 36 and the carbon target 37 to generate argon plasma, and the carbon target 37 is sputtered with argon ions in the argon plasma to knock out carbon atoms. The carbon atoms knocked out in this way are partially ionized by the fast electrons in the argon plasma to become carbon ions. This carbon ion is applied to the substrate 38 by the negative bias voltage applied to the substrate 38.
It is accelerated in the direction and reaches the substrate 38 and is deposited. As described above, in this conventional example, the high-hardness carbon film is formed on the substrate 38. However, since the high-hardness carbon film has high insulating properties, as the film formation progresses, a positive charge is formed on the formed film by carbon ions. Is accumulated. If this is left as it is, the effect of the negative bias voltage applied to the substrate 38 is reduced, and the film formation rate and the film quality are reduced. In this conventional example, however, an AC voltage is applied to the substrate 38 at appropriate times to form electrons in the plasma. By reaching the upper part and neutralizing the carbon ions, deterioration of the film forming rate and the film quality are suppressed. Another PVD device is, for example, an ion plating device, but when an insulating film such as a high hardness carbon film is formed by the ion plating device, a special neutralization for neutralizing the accumulation of positive charges is also required. Means are needed.

There are many conventional techniques for forming a high hardness carbon film with a CVD apparatus. (For example, Tezuka et al. “Proceedings of the 45th Academic Society of Applied Physics Academic Lectures”, (1984), p. 214, or Kato et al., “The 44th Proceedings of Applied Physics Society Academic Lectures”, (1983), P. .188). When a high-hardness carbon film is formed by a CVD apparatus, the film formation is a chemical reaction due to active chemical species, and the substrate is 50 to promote this reaction.
It is heated to about 0 to 1000 ° C.

Problems to be Solved by the Invention However, although the conventional techniques shown by the representative examples described above have their respective advantages, there are many problems particularly in practical application of a high hardness carbon film.

The problems in forming a high hardness carbon film with a PVD apparatus will be described below. Among the PVD devices, the ion plating device or the ion beam deposition device shown in the above-mentioned conventional example provides a relatively high hardness carbon film close to diamond at a substrate temperature close to room temperature in the conventional technique. It is excellent in that it can be formed at a high film formation rate. For example, in an ion beam deposition apparatus, an ion plating apparatus, etc., ions are accelerated by an electric field, and the surface of a film that is being formed is bombarded with high-speed ions. When the conditions for synthesizing diamond have been achieved and, for example, when a film is formed from a plasma of a hydrocarbon gas as is widely performed in the conventional technique, the undecomposed hydrocarbon bond taken in the film is removed. By improving the carbon purity of the high hardness carbon film by cutting with high speed ions, a high hardness carbon film having characteristics similar to diamond is formed. However, even if the substrate is a conductor such as a metal, a high-hardness carbon film that exhibits high insulation is formed on the substrate surface, so that positive charges are accumulated by the ions and the ions are not sufficiently accelerated by the electric field. Not only, but also the film forming rate decreases. The same applies when the substrate is an insulator.
As a countermeasure against this, in the conventional technique, for example, application of an AC voltage as described in the above-mentioned conventional example, or irradiation of electrons onto a forming film with an electron gun is performed. However, there are problems in industrialization such as the configuration and operation of the device are complicated, and the device is expensive.

Next, the problems of the high hardness carbon film forming apparatus using the CVD apparatus will be described. As described in the related art, in CVD, a film is formed by a chemical reaction by an active chemical species. Therefore, in order to accelerate the reaction and form an excellent high-hardness carbon film, the substrate is made to have a thickness of 500-100.
Heat to about 0 ° C. In such heating of the substrate, the substrate material for forming the high hardness carbon film is limited. For example, magnetic based on plastic film or plastic disc, or optical recording medium, plastic lens, or other metal micro Due to the mechanism, it becomes difficult to form a high hardness carbon film.

Further, since the CVD apparatus is provided with the additional device for heating the substrate as described above, the device cost increases. Further, the deposition rate of the high hardness carbon film by the CVD device is about 100 Å / min, which is smaller than the deposition rate of the PVD device of about 500 Å / min. This is also C
It is very disadvantageous in that the high hardness carbon film is applied to the product by the VD device and industrialized.

The object of the present invention is to solve the problems in the conventional techniques as described above when forming a high-hardness carbide film having an extremely high practical added value, to prevent the substrate from being heated, and to prevent the formation of complicated ions. It is an object of the present invention to provide a thin film forming apparatus capable of forming a high hardness carbon film having excellent characteristics similar to diamond at a film forming speed higher than that of the conventional technique without using a neutralizing means.

Means for Solving the Problems When forming, for example, a high hardness carbon film as a thin film, the means of the present invention for solving the above-mentioned various problems in the conventional technique is, for example, a hydrocarbon as a reactive gas. Acceleration neutralization means for converting mixed gas containing carbon atoms such as gas into plasma, accelerating at least ions in the plasma toward the substrate to form high-speed ions, and at least a part of the accelerated high-speed ions being high-speed neutral particles Is to form a high hardness carbon film with a thin film forming apparatus equipped with.

Operation By using the technical means according to the present invention as described above, the following operation occurs, and the problems in the conventional technology can be solved at once.

In ion beam deposition, ion plating, etc., since ions are deposited on the substrate while being accelerated toward the substrate, positive charges due to the ions are accumulated on the substrate, and deterioration of the film formation rate and film quality due to the accumulation of this positive charge is suppressed. Therefore, a special neutralizing means such as an electron gun was required. The thin film forming apparatus of the present invention is provided with a very simple ion accelerating neutralizing means, as shown in the following examples, and does not require any special neutralizing means. Further, for example, when a high hardness carbon film is formed by the thin film forming apparatus of the present invention, fast neutral particles having kinetic energy equivalent to fast ions in ion beam deposition, ion plating, etc., and fast ions are Since the surface of the film that is being formed is impacted, a high hardness carbon film can be formed whose substrate has excellent characteristics similar to diamond even at room temperature.

Further, as will be described in detail in Examples below, neutralization of ions in the thin film forming apparatus of the present invention is performed by electrons, but because some of the electrons accelerate excitation of undecomposed hydrocarbon gas molecules. In addition, the number of neutral particles and excited particles, which are the precursors of the high hardness carbon film, is remarkably increased as compared with the conventional PVD, and the film forming speed becomes faster.

Example FIG. 1 shows a schematic diagram of a first example in the case of forming a high hardness carbon film by the thin film forming apparatus of the present invention.

The first vacuum container 12 and the second vacuum container 1 are vacuum pumps 1.
It is evacuated to a high vacuum in advance at 3. Next, when forming a high hardness carbon film in the present invention, a hydrocarbon gas such as methane gas may be used as the reactive gas. Needless to say, the hydrocarbon gas may be acetylene gas, ethylene gas, ethane gas, butane gas, etc. other than methane gas. In addition, an auxiliary gas may be used to promote and stabilize the reaction and excitation of the reactive gas. As the auxiliary gas, for example, argon gas is desirable. Argon gas not only promotes and stabilizes the conversion of methane gas into plasma, but is also easy to handle and advantageous for industrialization, and is desirable for forming a high hardness carbon film having excellent characteristics. As the auxiliary gas, other than argon gas, for example, hydrogen gas may be considered, but hydrogen gas is not preferable because it is disadvantageous in industrialization in terms of handling. As shown in FIG. 1, a mixed gas containing these methane gas and argon gas is introduced into the first vacuum container 12 and set to a predetermined pressure. The mixed gas is turned into plasma in the plasma generation unit 9 by the excitation coil 4 and the high frequency power supply 8. As a plasma generating means, in addition to a high frequency power source, for example, a microwave,
Ion beam, electron beam, thermal decomposition, etc. have also been used in the prior art, but a high frequency power source is desirable because of high plasma efficiency and difficulty in raising the substrate temperature. Further, in the present embodiment, the excitation coil 4 is provided outside the plasma generator 9 as shown in FIG.
It is desirable to wind it on the outside and install it so that it is not directly exposed to plasma. This is because the constituent material of the excitation coil does not contaminate the plasma. For the plasma, for example, as shown in FIG. 1, the first electrode 5 is installed in the plasma generating unit 9, and the second electrode 10 is provided between the base 11 and the first electrode 5 so as to face the first electrode 5. It may also occur due to a potential difference such that 5 has a high potential. Ions in the plasma of the plasma generating unit 9 thus generated are installed between the base 11 and the first electrode 5 by installing the first electrode 5 in the plasma generating unit 9 as shown in FIG. 1, for example. When the facing second electrode 10 is provided and a potential difference is applied so that the first electrode 5 has a high potential, the first electrode 5 is accelerated toward the base 11. First
The shape of the electrode 5 is, for example, as shown in FIG. 1, when the methane gas 7 and the argon gas 6 are introduced from the rear of the first vacuum container 12, this mixed gas flows uniformly in the first vacuum container 12, In order to make the distribution of the film formed on the substrate 11 uniform, for example, a mesh shape is preferable. Further, for example, when the methane gas 16 and the argon gas 18 are introduced from the side of the first vacuum container 20 as shown in FIG. 2, the first electrode 17 may be, for example, a flat plate shape. Ions in the plasma are accelerated toward the substrate 11 due to the potential difference such that the first electrode 5 has a high potential with respect to the second electrode 10.
Some of the accelerated ions collide with the second electrode 10 to emit secondary electrons. A part of the accelerated ions is neutralized by the part of the secondary electrons in the vicinity of the second electrode to become a fast neutral particle, but the kinetic energy of the accelerated ions is larger than that of the secondary electrons. Therefore, the kinetic energy of the accelerated ions hardly decreases. Therefore, the high-speed neutral particles collide and deposit on the base 11 while having a large kinetic energy. There may also be high-speed ions that are accelerated and pass through the second electrode 10 to collide with and deposit on the substrate 11, but these ions pass through the secondary electrons emitted from the second electrode or pass through the second electrode 10. It is neutralized by the electrons in the plasma. In addition, since some secondary electrons accelerate the excitation of undecomposed hydrocarbon gas molecules, the number of neutral particles, excited particles, etc., which are precursors of the high hardness carbon film, is significantly increased as compared with the conventional PVD method, The film formation speed becomes faster.

Although plasma and undecomposed gas that have passed through the second electrode 10 exist between the second electrode 10 and the substrate 11, as shown in FIG. 1, the second electrode 10 and the substrate 11 or the substrate holder 11 ′ are connected to each other. If set to the same potential, the ions in the plasma,
Electrons reach the substrate in a molecular flow without being accelerated between the second electrode 10 and the substrate 11, so that charge accumulation does not occur. Further, the high-speed neutral particles may be ionized again, but the ions generated by this ionization have almost the kinetic energy of the high-speed neutral particles and therefore move toward the substrate as they are. Further, the electrons generated at the same time as the ions are pulled by the coulomb and are moved together with the ions. Therefore, for example, only the ions are not accumulated on the surface of the substrate 11 and no charge is accumulated.

As described above, in the present invention, charge accumulation in the substrate does not occur, there is no concern about deterioration of film quality during film formation and a decrease in film formation rate, and film formation on an insulating substrate is possible.

Next, a second embodiment of the present invention will be described. FIG. 3 shows a schematic diagram of the second embodiment of the present invention. In the first embodiment,
The accelerated ions collide with the second electrode 10 and are emitted 2
At least some of the accelerated ions were converted into fast neutral particles using secondary electrons. However, the amount of secondary electrons emitted varies depending on the amount of kinetic energy of ions, gas pressure, electrode material, etc., so the number of secondary electrons is small depending on the conditions,
It may be insufficient to neutralize the accelerated ions. The second embodiment of the present invention solves this problem. The basic structure of the second embodiment is the same as that of the first embodiment shown in FIG. 1, but the second electrode 10 of the first embodiment is replaced with a filament 37. First vacuum container 24
A methane gas 32 and an argon gas 31 are introduced therein, and plasma is generated by the high frequency power supply 34 and the excitation coil 30. First
A potential difference is provided between the electrode 33 and the filament 37 also serving as the second electrode by the DC power supply 29 so that the first electrode 33 has a high potential, and ions in the plasma are accelerated toward the substrate 40, and the filament heating power supply 38 Applies a voltage to the filament 37 to emit thermoelectrons. The accelerated ions are neutralized by these thermoelectrons and become fast neutral particles, but the kinetic energy of the accelerated ions at this time is much larger than the kinetic energy of the thermoelectrons, so the kinetic energy of the accelerated ions is high. Becomes the kinetic energy of fast neutral particles with almost no decrease. Since the number of thermoelectrons that neutralize the accelerated ions can be controlled independently of the accelerated ions by adjusting the filament heating power source 38, the number of thermionic electrons can be supplied without excess or deficiency. Therefore, the desired number of accelerated ions can be converted into high-speed neutral particles, charge accumulation in the substrate 40 does not occur, and there is no concern that the film quality will be deteriorated during film formation or the film formation speed will be reduced, and the insulating property will be improved. It is possible to form a film on the substrate. Also in this second embodiment, excitation of the undecomposed hydrocarbon gas molecules is promoted by some of the thermoelectrons, and the number of neutral particles and excited particles that are precursors of the high hardness carbon film is significantly increased as compared with the conventional PVD. , The film formation speed becomes faster.

As described above, according to the present invention, a high hardness carbon film having excellent characteristics similar to diamond is heated by using an extremely simple accelerating neutralization means for ions regardless of the substrate. It can be formed without any use, and its film forming speed is higher than that of the conventional technique. Further, even if an inert gas (eg, argon gas) is used as the auxiliary gas, a high-hardness carbon film having excellent characteristics can be formed, so that there is no danger of using hydrogen gas as the auxiliary gas as in the conventional technique. , Easy to industrialize. Moreover, since the present invention can be handled as a unit having the plasma generating means and the acceleration neutralizing means in the first vacuum container, it can be easily attached to an existing vacuum device.

The above is an example in which the present invention is applied to the formation of a high hardness carbon film. The present invention can be applied to other thin film formation by selecting introduced gas, applied DC power, applied AC power, etc. in addition to the formation of the high hardness carbon film. For example, titanium tetrachloride gas and methane gas are used to form a Tic film, and TiCl ₄ + CH ₄ → TiC _(s) + 4HCl _(g). To form a SiC film, silane gas and methane gas are used to form SiH ₄ + CH ₄ → Various kinds of films such as SiC _(s) + 4H2 ( _{2 (g)} can be formed.

Advantageous Effects of Invention The thin film forming apparatus of the present invention accelerates at least ions in a mixed gas containing a reactive gas that has been made into plasma as described above, and accelerates at least a part of the ions into electrons (secondary electrons). , Thermoelectrons, etc.). As an industrial effect, a highly hardened carbon film having excellent characteristics close to that of diamond, without heating the substrate, can be obtained by an extremely simple acceleration neutralization means as compared with the conventional one.
It can be formed at a much higher film formation rate than in the past. Further, as described above, since the thin film forming method and the forming apparatus of the present invention can be easily attached to the existing vacuum apparatus,
Very easy to industrialize. Furthermore, according to the present invention, various kinds of thin films can be formed by selecting and combining gas types, applied AC power, applied DC voltage, etc., and its industrial applicability is extremely large.

[Brief description of drawings]

FIG. 1, FIG. 2, and FIG. 3 are principle views of the thin film forming apparatus in the embodiment of the present invention, and FIG. 4 is a principle view of the thin film forming apparatus in the conventional example. 1 ... second vacuum container, 4 ... excitation coil, 5 ... first
Electrode, 10 ... Second electrode, 11 ... Substrate, 12 ... First
Vacuum container, 36 ... filament.

Claims (1)

[Claims] 1. A first vacuum container having a plasma generating means for converting a mixed gas containing a reactive gas into plasma, and at least ions in the plasma are accelerated toward a substrate, and at least the accelerated ions are at least accelerated. A thin film forming apparatus comprising: an accelerating neutralizing means, a part of which is neutral particles, and a second vacuum container in which a substrate is installed and which is connected to a first vacuum container so that a gas can flow therein.