JPS6325070B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to an apparatus that uses glow discharge to diffuse a substance from the surface of an object to be processed or to form a coating film thereon. A direct current voltage is applied between a cathode consisting of auxiliary electrodes arranged opposite to each other and an anode on the wall of the container or inside the container, and a glow discharge is generated between these electrodes to perform surface treatment on the object to be treated or to remove the coating film. The present invention relates to an apparatus for forming. [Background of the Invention] Conventionally, there is a plasma CVD method as a surface treatment method using glow discharge. As a well-known example of a device that performs a DC glow discharge type plasma CVD method,
There is 57-188670. This device is as shown in FIG.
A conductive member 2 connected to the cathode of a DC power source 6 is provided in a container 1 in a reduced pressure atmosphere of Torr, and an auxiliary electrode 3 having approximately the same potential as the conductive member 2 is provided opposite to the conductive member 2. , the container 1 is connected to the anode of the power source 6, and an interaction is generated between the glow discharge on the surface 21 of the treated part of the conductive member 2 and the glow discharge of the auxiliary electrode 3 to perform glow discharge treatment, and the treated part The surface 21 is coated with a target substance.
In such a processing apparatus, since the ionization density of the reactive species can be increased near the part to be processed, a high-quality film can be produced at high speed compared to other methods using only simple glow discharge. However, in order to achieve even faster processing using the method shown in Figure 2, it is necessary to increase the applied voltage to increase the energy of the glow discharge, or to increase the energy of the glow discharge by increasing the applied voltage.
It is necessary to make the interaction between the glow discharge stronger by reducing the gap between the electrode and the auxiliary electrode. However, in the case of the former method, increasing the energy of glow discharge directly increases the glow discharge current density on the surface of the workpiece, which in turn increases the amount of energy supplied to the surface of the workpiece, so the applied voltage If the temperature is increased, the temperature of the product to be processed will rise. Therefore, if there is a limit to the applicable temperature depending on the material of the object to be treated, there is a limit to the application of this method. For example, by TiCl ₄ and CH ₄ on Al alloy
When coating TiC, the reaction temperature of TiC is
Requires temperature of 900℃ or higher. In this method, Al alloy will be heated to almost the same temperature, but since the melting temperature of Al alloy is around 600℃, it will be difficult to apply TiC coating with this method. . On the other hand, in the case of the latter method, that is, when the gap between the auxiliary electrode and the workpiece is made smaller, the interaction between the glow discharges becomes stronger as the gap is made smaller, resulting in a discharge with a high current density, which accelerates the reaction. be done. However, as the gap becomes smaller, the uniform supply of new reactive gas into the plasma space near the surface to be treated becomes insufficient, and the residence time of spatter atoms emitted from both surfaces becomes longer in that space, causing the coating to deteriorate. It gets mixed into the layer and reduces the purity of the coating. This phenomenon is particularly problematic in the formation of functional films. From the above, it is possible to reduce the ionization density of the gas by plasma without heating the workpiece to high temperatures, and in a state in which the gas involved in the reaction is uniformly and freshly distributed over the entire workpiece surface. By activating reactive species by increasing the temperature without causing non-uniformity on the surface, it is expected that materials that are formed at low temperatures (e.g. amorphous silicon, 250°C) or that films formed at low temperatures will exhibit special properties. It is desired to develop a surface treatment technology that can rapidly form a highly pure, homogeneous film (for example, TiC at 600°C). [Object of the invention] The object of the present invention is to develop a direct current glow discharge type plasma.
In the CVD method, the ionization density of the supplied gas is increased on the surface of an auxiliary electrode placed opposite the workpiece.
Another object of the present invention is to provide a surface treatment apparatus capable of uniformly and sufficiently supplying a fresh gas to a workpiece to form a high-quality coating at high speed without increasing the temperature of the workpiece. [Summary of the Invention] The present invention provides a container whose interior can be depressurized, an auxiliary electrode disposed in the container in close opposition to a member to be processed, and a gas involved in reaction or processing in the container. a gas supply system, and a voltage source for applying a DC voltage between the treated member and the auxiliary electrode as cathodes and the container or an anode inside thereof to generate a glow discharge therebetween. In the surface treatment apparatus using glow discharge for a workpiece, the auxiliary electrode is arranged at least on the side facing the workpiece to reduce the ionization density of the glow discharge on the surface of the workpiece of the auxiliary electrode to the surface of the workpiece. It is characterized by having a concavity and convexity that is higher than that of the concave and convex portion, and a gas supply port for supplying the gas that opens into the recess formed by the concavity and convexity. In the apparatus of the present invention, the ionization density of the glow discharge on the surface of the auxiliary electrode on the workpiece side is controlled by the interaction of the glow discharge on the uneven portion of the auxiliary electrode.
By increasing the ionization density of the glow discharge on the surface of the workpiece, the proportion of ionization, excitation, and radicals of reactive species near the surface of the workpiece can be increased without heating the workpiece to a high temperature, and Introducing fresh gas involved in the reaction into the glow discharge area,
Unnecessary impurities caused by electrode spatter are reduced and turned into plasma, and the gas with high ionization density is guided near the workpiece by passing through the glow discharge region between the workpiece and the auxiliary electrode to form a coating. form. As mentioned above, in conventional surface treatment methods, in order to rapidly treat the surface or form a film of reactive species, it is necessary to increase the applied voltage or current density, or increase the temperature. However, when a high voltage is applied, surface atoms are emitted by sputtering on the surface of the member to be processed, and the temperature of the member to be processed itself increases, which may adversely affect the formed film. In addition, an increase in temperature places restrictions on the material of the workpiece to be used, and may change the properties of the material of the workpiece and the properties of the coating. Further, there was a problem in forming an amorphous film such as amorphous silicon. As a result of intensive research, the inventors of the present invention have conducted intensive research to enable surface treatment that can form a film at high speed and produce a highly pure and homogeneous film without raising the temperature of the product itself to a high temperature. In the surface treatment method using direct current glow discharge, it is possible to increase the ionization density near the surface of the workpiece without increasing the current density on the surface of the workpiece as in the conventional method, and to constantly introduce new gas into that spatial region. The inventors have discovered that this can be achieved by supplying gas, lowering the discharge voltage, and evenly supplying and distributing fresh gas to the surface of the member to be treated, and have arrived at the present invention. The gases to be supplied include one or more of hydrogen gas or argon gas, silicon-based gas such as silane which is a substance that diffuses or forms a coating film on the member to be treated, metal halide gas, methane gas,
A mixed gas of at least one of nitrogen gas, hydrocarbon-containing gas, ammonia gas, sulfide gas, metal gas, metalloid halide gas, metalloid gas, and the like can be used. In the present invention, the shape and structure of the auxiliary electrode are important. That is, in the device of the present invention,
In areas that are relatively far away from the workpiece in terms of thermal energy, that is, on the side of the auxiliary electrode facing the workpiece, glow discharge interacts with the uneven parts, causing more ionization than in other glow discharge areas. Multiple irregularities that cause density (these irregularities are caused by the interaction of glow discharges generated on mutually contacting or opposing surfaces of the irregularities, so that the ionization density of the glow discharge there is different from that of the individual without interaction) ionization density is higher than the ionization density of the glow discharge region), and furthermore, a gas supply port is opened in the uneven portion so that the new gas of the reactive species is uniformly distributed in the glow discharge region. has been formed. In the present invention, in order to perform high-purity surface treatment with even fewer impurities, it is desirable to provide a mechanism for continuous or intermittent relative movement between the member to be treated and the auxiliary electrode. In other words, when performing surface treatment or coating while supplying fresh gas between the auxiliary electrode and the workpiece, if the auxiliary electrode and workpiece are always fixed, foreign atoms from the discharge surface will be removed by the sputtering action of the plasma. Contamination or retention of decomposed atoms in the supplied gas may occur, resulting in a decrease in the purity of the surface treatment layer and a decrease in the surface treatment or coating speed. Measures such as moving the gas supply port or moving the relative position of the auxiliary electrode and the workpiece are effective, but although moving the gas supply port is effective to some extent, impurity atoms from each discharge surface are removed from the plasma. When considering removal from space, the most effective measure is to move the relative positions of the auxiliary electrode and the member to be processed. This is done by moving at least one of the auxiliary electrode or the object to be processed, and it is particularly desirable to provide a space in which neither one of them will generate discharge. Alternatively, the same effect can be obtained even if the glow discharge is momentarily stopped. That is, if the discharge is momentarily stopped in a state where sputtered atoms are mixed into the plasma space and remain there, the sputtered atoms are cooled and easily exhausted. When relatively moving the position, there are an intermittent movement type in which discharge is generated for a certain period of time and then the movement is made, and a continuous movement type in which the position is moved continuously. By such measures, impurities can be extremely reduced, and the influence of non-uniform discharge depending on the location of the member to be treated can also be reduced. In addition, by discharging residual gas unnecessary for the reaction and making it easier to supply gas with a high proportion of reactive species, a high-purity film can be formed quickly. [Embodiments of the Invention] Example 1 FIG. 1 is a diagram showing an example of the present invention.
A member to be processed 2 connected to the cathode of a DC power supply 6 was placed in a reduced pressure container 1, and an auxiliary electrode 3 having the same potential as the member to be processed 2 was placed opposite to the member to be processed 2. The container 1 is connected to the anode of a power source 6. This auxiliary electrode is as illustrated in FIG. That is, on the side of the auxiliary electrode 3 facing the workpiece, there is a gas supply port 4 with a diameter of 0.02 mm in this example.
A large number of gas supply ports are arranged in an orderly manner, and a plurality of plates 5, each having a height of 15 mm and a thickness of 2 mm, are arranged in a protruding manner in the longitudinal direction at intervals of 7 mm in the vicinity of these gas supply ports. First, the pressure inside the reaction vessel 1 was reduced to 10 ^-5 Torr or less using the vacuum pump 7. After that, TiCl ₄ and CH ₄ gases with hydrogen gas as a carrier are introduced into the container 1 through the gas supply port 4 from the gas supply system 8, and the gas is heated to 2 Torr.
A glow discharge was generated by applying a DC voltage of 6 while maintaining the pressure at . In this example, the member to be processed 2 is
A 100mm x 100mm x 3mm plate of SUS304 was used. It was observed that the glow discharge was strongest in the space surrounded by the convex plate 5 of the auxiliary electrode. In this state, while maintaining the temperature of workpiece 2 at 600℃, TiC
coating was carried out. The sustaining voltage of discharge is
It was almost 500V. The introduced gas is activated by decomposition, ionization, etc. in the discharge area where the interaction between the glow discharges generated on each surface of the plate 5 of the auxiliary electrode occurs, and then the gas is activated by the gas supply port in the auxiliary electrode. It was confirmed that by supplying new gas from No. 4, the reaction gas was sent to the surface of the article to be processed 2. As a result, a sufficiently good TiC coating was obtained. On the other hand, in the conventional method, a flat plate-shaped auxiliary electrode 3 as shown in Fig. 2 is attached to the workpiece 2 (SUS304) by 7 mm.
When similar processing was performed by bringing the auxiliary electrode close to the workpiece to generate a glow discharge interaction between the auxiliary electrode and the workpiece, the discharge voltage was approximately 800V and the temperature of the workpiece was 900℃.
It was hot. A comparison between the above embodiment of the present invention and the conventional system is shown in the table below.

【table】

[Table] If we elaborate on this, it is as follows. (a) When forming a TiC film using the CVD method, TiCl ₄ +
According to the reaction of CH ₄ → TiC + 4HCl, due to the free energy of formation, if only thermal energy is used, the reaction temperature needs to be 920℃ or higher, but it is generally carried out at about 1020 to 1040℃ from the viewpoint of crystallinity etc. It is. By using plasma for this reaction, the processing temperature can be lowered, and compared to the conventional method described above,
At 900°C, properties equivalent to those of a film formed using only thermal energy were obtained in terms of hardness (Hv2500) and adhesion. However, if the treatment temperature is lowered further using the conventional method, the hardness of the coating will decrease, and the temperature will exceed 600℃.
Then it becomes Hv900. The reason for this is that the energy density of the discharge is lowered to lower the processing temperature, which lowers the reaction energy for TiC formation and does not result in a healthy TiC bonding state, or that unreacted products may be present in the coating. (HCl, etc.). In this way, in the conventional method, since the heating of the processed object and the activation (reaction) of the processing gas are performed in the same discharge area, each cannot be controlled independently, and the discharge is activated to lower the temperature. When the energy density was decreased, the discharge energy required for the reaction also decreased, which affected the reaction and made it impossible to obtain a sound film. On the other hand, in the embodiments of the present invention, the energy required for the reaction can be controlled independently within the uneven auxiliary electrode, and the temperature of the object to be treated can be controlled arbitrarily while maintaining the reaction density. A healthy TiC film similar to that of the conventional method was able to be formed at a lower temperature of the treated object than in the conventional method. (b) As mentioned above, in the embodiments of the present invention, the discharge voltage is lowered by controlling the gap etc. in order to maintain the high density of the discharge (concave and convex auxiliary electrode) for causing the reaction, and The temperature of the item to be processed can be lowered to process it. Therefore, the discharge voltage is in a low state. On the other hand, the conventional method requires a large amount of electric power because the object to be processed is heated to a high temperature. That is, the applied current and voltage become higher. (c) Processing time 1 according to the embodiment of the present invention and the conventional method
The film thickness over time was 12 μm in the example of the present invention and 10 μm in the conventional method. From this result, the film formation rate is 12 μm/h in the embodiment of the present invention and 10 μm/h in the conventional method. As described above, the embodiment of the present invention is a processing technology that enables high-speed film formation.
This is due to the increased reaction density within the auxiliary electrode. Incidentally, in the commonly used CVD method using only thermal energy or RF plasma CVD method, the film formation speed is even slower than in the embodiments of the present invention or the conventional method. In the embodiment of the present invention, the amount of reactive gas activated near the workpiece 2 was greater than in the conventional method in which glow discharge interaction was generated only between the flat plate-shaped auxiliary electrode and the workpiece. comes to exist. In addition, the discharge sustaining voltage due to the glow discharge in this example is the lowest discharge voltage at the interaction part of the glow discharge in the space surrounded by the convex plate of the auxiliary electrode, so it should be lower than that in the conventional method. Can be done. Furthermore, even when the applied power is increased in this state, rapid processing is possible without significantly increasing the temperature of the processed item. Example 2 Ti coating was performed using the apparatus shown in FIG. 1 and the same auxiliary electrode as in Example 1. First, operate the vacuum pump 7 to open the reduced pressure container 1.
After increasing the pressure to about 10 ^-2 Torr, hydrogen-based
TiCl ₄ is introduced from the gas supply port 4 of the auxiliary electrode 3,
The flow rate and pressure are maintained by adjusting the mass flow controller and exhaust pressure, and a DC voltage of 400 V is applied in the same manner as above to form a glow discharge. TiCl ₄ is decomposed by the discharge energy, and 100 mm x 100 mm x 2
When Ti was coated on the workpiece 2 (SUS304) of mm, the temperature of the surface of the workpiece 2 was raised to 600
Coating was possible at temperatures below ℃. On the other hand, as a conventional method, the same treated member as above was coated with Ti using a method of thermally decomposing TiCl ₄ . A comparison between the above embodiment of the present invention and the conventional method is shown in the table below.

[Table] As is clear from this table, according to the embodiments of the present invention, 2 μm in 1 hour at a processing temperature of less than 600°C.
We were able to form a Ti film of Therefore, the Ti film forming temperature is 2 μm/h. This coating was identified to be Ti by X-ray diffraction. On the other hand, in the conventional method, the Ti coating is formed by thermally decomposing the processing gas of TiCl ₄ and H ₂ , so the precipitation temperature needs to be 2000°C or higher due to the free energy of reaction formation. The parts
Since SUS304 is a steel material, Ti precipitates at temperatures above 1200℃ due to its catalytic action. (1400℃ in this example)
We were able to form a Ti film. ) Therefore, the conventional method cannot be applied depending on the material of the member to be treated. Moreover,
Despite such high-temperature treatment, in the conventional method, a 1 μm thick Ti film was formed after 2 hours of treatment, so the film formation rate was 0.5 μm/h, which is much faster than in the example of the present invention. It's late. As described above, according to the embodiments of the present invention, a Ti film can be formed on a SUS member to be processed at low temperature and at high speed.
Therefore, it can be easily applied to iron parts that become brittle at high temperatures.
Can be treated with Ti coating. Example 3 TiN coating was carried out using the same auxiliary electrode as in Example 1 and the apparatus shown in FIG. Also,
TiN coating was performed using conventional plasma CVD method. The comparison is shown in the table below.

【table】

〔Effect of the invention〕

According to the present invention, by increasing the ionization density of the glow discharge on the surface of the auxiliary electrode on the workpiece side due to the interaction of the glow discharge of the uneven portion of the auxiliary electrode, the current density on the surface of the workpiece is increased. It is possible to increase the ionization density near the surface of the member to be treated without raising the temperature of the member to be treated, and to perform high-purity, homogeneous surface treatment at a high speed without being affected by spatter atoms etc. emitted from the electrode surface. In addition, high ionization density discharge for ionizing, excitation, and dissociation of gas can be independently controlled by the uneven shape of the auxiliary electrode.
Furthermore, the temperature of the member to be treated can be controlled arbitrarily since the interaction between the auxiliary electrode and the glow discharge of the member to be treated is not used. Furthermore, since film formation and gas activation are performed separately, there is less contamination of impurities into the film.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an embodiment of the present invention, Fig. 2 is a schematic diagram of a conventional surface treatment apparatus, Fig. 3 is an enlarged perspective view of the auxiliary electrode in Fig. 1, and Fig. 4 is a schematic diagram of an embodiment of the present invention. A schematic perspective view of a member to be processed and an auxiliary electrode in another embodiment, and FIGS. 5 and 6 are a surface view and a partially sectional view of the auxiliary electrode. DESCRIPTION OF SYMBOLS 1... Reaction container, 2... To-be-processed member, 3... Auxiliary electrode, 4... Gas supply port, 5, 5a... Convex part, 6... DC power supply, 7... Exhaust pump, 8... Gas supply system.

Claims (1)

[Claims] 1. A container whose interior can be depressurized, an auxiliary electrode disposed within the container in close opposition to a member to be processed, and a gas involved in reaction or processing supplied into the container. It is equipped with a gas supply system, and a voltage source for applying a direct current voltage between the treated member and the auxiliary electrode as cathodes and the container or an anode inside the container to generate a glow discharge therebetween. In a surface treatment apparatus using glow discharge for a member to be treated, the auxiliary electrode has at least one side facing the member to be treated;
The gas supply has an unevenness that makes the ionization density of the glow discharge higher on the surface of the auxiliary electrode on the side of the member to be processed than that on the surface of the member to be processed, and opens into the recess formed by the unevenness. 1. A surface treatment device using glow discharge, characterized by having a gas supply port for. 2. A surface treatment apparatus using glow discharge according to claim 1, which has a mechanism for relative movement between the member to be treated and the auxiliary electrode.