JPH0233786B2 - KAGOBUTSUMAKUNOKEISEIHOHO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming a compound film by reactive vapor deposition using hollow cathode discharge.

Conventional technology The activated reactive vapor deposition method has traditionally been used to form compound films such as carbides and nitrides used for tools, decorations, corrosion-resistant coatings, etc., and SiC films, which are also being used as semiconductors. There is. This is a method of ionizing a reaction gas to vapor deposit a compound in order to increase reaction efficiency. Conventional examples include JP-A-48-60088, JP-A-49-52186, and JP-B-Sho 57-2271. Examples thereof include those described in Japanese Patent Publication No. 58-41351 and the like.

For example, Japanese Patent Application Laid-Open No. 49-52186 discloses that a carbide coating is formed by reactively depositing activated metal vapor and hydrocarbon gas atoms in the vapor phase in the space between the substrate and the metal source. A source metal is heated by an electron beam and vaporized in a vacuum chamber, providing metal vapor electrons to a reaction zone. Then, a hydrocarbon gas is introduced into the reaction zone, and some electrons of the metal heating electron beam are deflected into the reaction zone by a low voltage electric field from a deflection electrode provided in the reaction zone, and the atoms of the metal vapor and gas are heated. is activating. Activation of the reactants increases the probability of reaction, allowing the reaction between metal vapor and hydrocarbon gas to occur with high efficiency.

Furthermore, the above-mentioned Japanese Patent Publication No. 58-41351 describes an activated reaction vapor deposition method for forming a metal carbide or nitride film on a substrate, and in this case, a hollow hot cathode type electron gun is used. An electron gun is used to control the temperature of the substrate and the pressure of the reaction gas to obtain a stoichiometrically stable coating with high efficiency.

Furthermore, Japanese Patent Publication No. 57-2271 describes an activation reaction vapor deposition apparatus for forming a metal carbide or nitride film on a substrate, and in this case, separate supply of atmospheric gas and reaction gas is required. In order to avoid complicated control, the reaction gas is introduced into the processing chamber via a hollow hot cathode type electron gun.

Problems to be Solved by the Invention However, in such reactive deposition using hollow cathode discharge, group elements such as boron and silicon are deposited, and hydrocarbons, nitrogen, ammonia, etc. are used as the reaction gas. When forming carbide and nitride films, the activation energy is large;
Since the reaction rate is slow, the amounts of carbon and nitrogen become saturated below the stoichiometric composition at low substrate temperatures, making it impossible to obtain a compound film with the desired composition.

On the other hand, as a recent trend, higher rate and lower temperature processes are becoming necessary due to demands for base material selectivity and cost reduction due to applications in various fields as mentioned above.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a compound film that can meet these demands and also allows the composition of the compound film to be controlled arbitrarily, which has been difficult with conventional low-temperature processes.

Means for Solving the Problems In order to achieve this object, the method for forming a compound film according to the present invention provides a method for forming a compound film using a hollow cathode discharge. It is characterized by drawing some of the electrons into the reactive gas inlet using an electric field, activating the reactive gas, and increasing the reactivity in chemical vapor deposition.

Effect In the method of the present invention configured as described above,
Electrons are drawn into the reactive gas inlet by applying a positive direct current or alternating current voltage to the reactive gas inlet nozzle, thereby making it possible to generate reactive gas plasma and perform activation.
Furthermore, different reaction gases can be activated separately using a plurality of activation nozzles, thereby making it possible to arbitrarily change the composition of the multi-element compound (for example, B-C-N, etc.). Therefore, not only high melting point transition metals but also elements that require large activation energy can be controlled arbitrarily in the amount of carbon and nitrogen in the carbide and nitride films, and the amount of carbon and nitrogen at or above the stoichiometric composition can be obtained. It is possible to form a compound film containing an amount.

Embodiments Hereinafter, the present invention will be described by way of embodiments with reference to the accompanying drawings.

FIG. 1 shows the configuration of an example of an apparatus for carrying out the method of the present invention, in which 1 is a vacuum vessel, inside this vacuum vessel 1 are a water-cooled copper hearth 2 containing an evaporated substance;
A reaction gas introduction nozzle 3, a hollow cathode electron gun 4, a substrate 5, and a heater 6 are arranged as shown. In addition, 7 is a power supply for operation, 8 is a DC power supply, 9
is a DC or AC power source, and each of these power sources are connected as shown.

A hollow hot cathode discharge is caused by the action of a power source 7 between the water-cooled copper hearth 2 containing the evaporated material and the electron gun 4, and this discharge is generated at a low voltage and large current (~30V, 100~300A). be. In this manner, the evaporated substance within the hearth 2 is melted by the electron beam emitted by the electron gun 4. At the same time, the evaporated atoms are activated by collisions between the evaporated atoms and electrons. The action of these active atoms promotes the reaction between the reaction gas from the reaction gas introduction nozzle 3 and the evaporated substance on the substrate 5. Furthermore, since the ionization efficiency is high, a film with better adhesion can be obtained by applying a negative bias between the hearth 2 and the substrate 5 using the DC power supply 8 to draw ions into the substrate 5.

Even in this state, carbide and nitride films can be obtained at any substrate temperature and with any composition up to the stoichiometric ratio for transition metals such as titanium, zirconium, hafnium, vanadium, niobium, and tantalum, and metals such as Al and Ga. can.

However, for elements such as silicon and boron, which have a large activation energy for compound formation, when the substrate temperature is low, the amount of carbon and nitrogen in the film compound becomes saturated at a low value.
Stoichiometry cannot be obtained.

Therefore, in the present invention, a positive DC or AC voltage of several tens to hundreds of volts is applied between the electron gun 4 and the reaction gas introduction nozzle 3 by a power source 9. As a result, some of the electrons in the hollow cathode discharge space are drawn into the reactive gas introduction nozzle 3, whereby collisions occur between the electrons and reactive gas molecules, resulting in a high-density discharge state. As a result, the reaction gas is partially ionized and activated to a neutral excited state, promoting the reaction on the substrate 5.

Next, specific examples will be described.

First, to explain the case where a silicon carbide film is formed using the apparatus shown in FIG. 1, the silicon in the hearth 2 is melted and evaporated by hollow cathode discharge, and at the same time, acetylene gas is introduced as a reaction gas through the reaction gas introduction nozzle 3. is introduced to form a silicon carbide film on the substrate. In this case, when no positive voltage is applied to the reaction gas introduction nozzle 3, as shown in Figure 2, even if the acetylene flow rate is increased or the film deposition rate is decreased, the substrate temperature remains at 500°C. A film with a C/Si composition ratio of 0.7 or more cannot be obtained.

On the other hand, when a voltage is applied to the reaction gas introduction nozzle 3 and vapor deposition is performed in a discharge state with a nozzle current of 6 [A], as shown by the broken line in Fig. 2, C/Si
The composition ratio can be increased.

FIG. 3 shows the experimental results when a direct current positive voltage was applied to the reaction gas introduction nozzle. The graph shows the case where the acetylene flow rate is 40 c.c./min, the graph shows the case where the acetylene flow rate is 60 c.c./min, the distance between the hearth 2 and the substrate 5 is 35 cm, and the deposition rate is 0.05 μm/min.
It is min. As can be seen from FIG. 3, when the current is 5 A, for example, a film with a C/Si composition ratio of ~1 can be formed as shown in the graph, whereas when no voltage is applied to the reaction gas introduction nozzle 3 under the same conditions, C/Si can be formed. The Si composition ratio is ~0.5. The Vickers hardness of the obtained film is ~1.0 for a C/Si composition ratio of 1.0.
It is more than 3500Kg/ ^cm2 , which is the bulk nominal value or more.

Next, the Si--N system will be illustrated. In this case too
Similar to the SiCx film, Si is evaporated and the reaction gas is N ₂ ,
A SiNx film is formed using NH ₃ or a N ₂ -H ₂ mixed gas. Figure 4 shows an example of a SiNx film formed using NH ₃ as the reaction gas, and shows the film composition when bias (50V, 6.5A) is applied to the reaction gas introduction nozzle and when it is not applied (floating). Shows substrate temperature dependence. In addition, in Fig. 4, the deposition rate is 0.02 μm/min, and the flow rate of NH ₃ is 40 c.c./min.
It is. As can be seen from Figure 4, when a voltage is applied to the reaction gas introduction nozzle, the N/Si composition ratio is much larger at the same substrate temperature than when no voltage is applied, and moreover, the composition The range of ratios becomes significantly larger.

FIG. 5 shows an example of the BN system. to reaction gas
The dependence of the composition of the deposited film on the nozzle current when N ₂ is used is shown. When no voltage is applied to the nozzle, the composition ratio is about N/B 0.05, but when a voltage is applied, a film with N/B 1.0 can be obtained.

Effects As explained above, according to the present invention, in reactive vapor deposition using hollow cathode discharge, the reactive gas is activated by applying a bias voltage to the reactive gas inlet and drawing electrons into the reactive gas.
By increasing the reactivity, the film composition can be changed easily and arbitrarily. Therefore, it is possible to arbitrarily control the carbon and nitrogen contents of carbides and nitride films of not only high melting point transition metals but also of elements that require large activation energy to achieve a stoichiometric composition or higher carbon and nitrogen contents. A compound film containing the compound can be easily formed.

Note that the method according to the present invention can be applied not only to transition metals but also to metal-gas combinations that are difficult to deposit in a normal reactive (accompanied by a chemical conversion reaction) process. It can also be used to accelerate deposition rates. Furthermore, when carrying out the method of the present invention, the reaction gas can be easily activated using a DC or AC power source, which is lower in cost than a high-frequency power source, etc., and the field of application of the HCD ion plating apparatus can be expanded. .

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an apparatus implementing the method of the present invention, and FIGS. 2 to 5 are explanatory diagrams of the embodiment. In the figure, 1: vacuum container, 2: hearth, 3: reaction gas introduction nozzle, 4: hollow cathode electron gun, 5: substrate, 9: DC or AC power supply.

Claims (1)

[Claims] 1 In reactive vapor deposition using hollow cathode discharge,
A part of the large amount of electrons present in the plasma generated by hollow cathode discharge is drawn into the reactant gas inlet by an electric field, activating the reactant gas and increasing the reactivity in chemical vapor deposition, allowing the chemical composition of the compound film to be arbitrarily adjusted. A method for forming a compound film, characterized in that it can be controlled.