JPS6041571A - Preparation of solid thin film on surface of object to be processed - Google Patents

Abstract

PURPOSE:To obtain flat and dense film having specific property by allowing solid powder particles accelerated to high velocity to collide with the surface of an object to be processed using an electrostatic method. CONSTITUTION:Agglomerated mass of particles or a single particle separated by the effect of electric field are (is) moved reciprocally between electrodes provided by arranging parallel flat plate electrodes 13, 14 to face each other in vacuum. Simultaneously, a high voltage electric field is formed by impressing high voltage to the electrodes 13, 14 to charge and accelerate above-described solid powder particles 1. Solid thin film 3 is formed by impacting and sticking said charged and accelerated powder particles 2 on the surface of an object 4 to be processed. By this method, flat and dense film having specific property is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a thin film manufacturing method in which solid fine powder particles accelerated at high speed collide with the surface of a solid workpiece using an electrostatic method and are deposited to form a solid thin film. It is about the method.

Conventional techniques for manufacturing a film by imparting kinetic energy to minute units of matter by some kind of acceleration means, colliding with the surface of a solid material, and depositing the kinetic energy include, for example, those based on the collision of atomic units of ions. There are thermal spraying techniques based on ionization deposition (plasma method, sputtering method), ion beam deposition, and the collision of larger units of thermally melted solid materials. Although relatively high-quality film materials can be obtained in the former method, it is difficult to set appropriate film formation conditions, and the peripheral technology required for this purpose, such as controlling the atmospheric gas, tends to be complicated and the equipment tends to be large-scale. Ta. On the other hand, in the latter method, the surface of the workpiece is built up by spraying a high-temperature substance melted in the air, which inevitably avoids deterioration of the quality of the formed film material or thermal deterioration of the workpiece. There was a drawback that it could not be done.

The thin film manufacturing method of the present invention can be said to have the same principle as the former method in that it uses electrostatic acceleration means, but the object of acceleration is a fine solid substance (powder particles) that is much larger in size than ions, and moreover, It is characterized by the use of high-speed impact phenomena between substances for film formation. Therefore, the film formation mechanism or the properties of the formed film material will be different in both cases. In other words, when a fine solid substance hits the surface of a solid material at high speed, a high temperature and high pressure state occurs due to the supply of energy with high power density, resulting in changes in the crystallographic structure of the impacted substance or changes in the structure of different materials. A chemical reaction can be expected.

Figure 1 (a) shows the basic principle of this thin film manufacturing method, showing the process in which a single powder particle is charged and electrostatically accelerated in an electric field to obtain high speed, collide with and adhere to the surface of the workpiece. represents. That is, the flat electrodes 15 and 15 connected to the DC high voltage power supply 5 constitute an anode and a cathode, respectively, and an electric field E is created between these electrodes, the strength of which depends on the distance d between the electrodes and the applied voltage. is added. Initially, in the electrically neutral powder particles 17 that existed near the anode surface, field emission of electrons due to the action of the electric field or conduction due to contact with the electrode surface occurs, and the movement of electrons e from the powder particles to the anode occurs. This causes a positive charge amount to be applied. ((A) in the same figure). As a result, the charged powder particles are electrostatically accelerated in the direction of the electric field E in the figure to obtain a high speed, and their speed reaches the maximum speed V immediately before colliding with the cathode surface. ) (B) in the same figure). Since the high-speed powder particles instantaneously release their kinetic energy upon collision, they are impact-plastically strengthened and deposited on the cathode surface. ((C) in the same figure).

Figure 1(b) shows that practical fine powder particles, which are normally in an agglomerated state, are separated from the agglomerated state into a single fine powder particle in an electric field, and undergo the above-mentioned charging and electrostatic acceleration behavior. The process leading to involvement in membrane formation is shown. That is, as a result of the aggregated particle population being charged near the anode surface based on the above-mentioned charging mechanism ((D) in the figure), the charged charges are electrostatically dispersed into smaller particle populations due to the repulsion force. ((E) in the same figure). Since the separated particle group has a positive charge, it is electrostatically accelerated toward the cathode and collides with its surface, where it is further mechanically separated by the impact force ((F) in the figure). Particles colliding with the cathode surface are a group of relatively small diameter particles that achieve high speed and adhere to the surface, but particles with relatively large diameters that do not have enough kinetic energy to adhere are attached to the negative electrode. It is electrostatically recharged and electrostatically accelerated toward the anode. In this way, between the opposing flat electrodes, electrostatic dispersion and mechanical separation are repeated during the reciprocating motion between the electrodes in the direction of the electric field, and as a result, the initial aggregated particles pass through smaller aggregated particles and become individual particles. Separation progresses to single particles. Further, when the aggregated particles are separated, a space charge field due to the large number of charged powder particles is formed between the poles, so that the individual powder particles are repulsed by the electrostatic force. Therefore, the powder particles between the electrodes are repeatedly charged and accelerated in the direction of the applied electric field, and move back and forth to diffuse toward the electrode periphery.

The velocity obtained by powder particles due to electrostatic acceleration between flat electrodes is theoretically V = (2qVa/m)' = (6βEOE2d /rp
o)' (where q, m, γ and ρ are the charge amount, mass, radius and density of the powder particles, respectively, Va, E and d are the applied voltage, applied electric field strength and distance between the electrodes,
β is the charge coefficient, and ε0 is the vacuum dielectric constant), which indicates that powder particles with a smaller particle size can achieve higher speeds. Therefore, during the reciprocating movement between the electrodes, the particle diameter becomes finer, and the high-speed particles that have acquired enough kinetic energy to adhere selectively adhere to the surface of the electrode (workpiece), resulting in a thin film formed by the accumulation. Formation will proceed. FIG. 4 is an example of experimental results demonstrating that initial aggregated particles are separated into almost single powder particles during reciprocating motion based on charging and acceleration between parallel plate electrodes. In other words, the average specific charge q/m (white blank circle) of charged powder particles pulled out from between the electrodes without reciprocating motion is extremely low, whereas the q/m (black circle) when reciprocating motion is performed. shows a value of 0 near the theoretical value ζ of a single powder particle, indicating that the drawn particles have reached the theoretical velocity mentioned above. In this way, the ability to accelerate highly cohesive (A fine powder particles) to a high speed ζ in accordance with the theory of electrostatic acceleration is due to the effect of the flat electrode.
This is also a feature of the present thin film manufacturing method. Furthermore, due to the diffusion movement caused by the space charge field of the powder particles, a substantially uniform thin film can be formed on the surface of the workpiece over a fairly wide range. In FIGS. 1(a) and 1(b), it is assumed that particles adhere to the entire cathode surface, but the same phenomenon occurs even when the particles are attached to the anode surface. However, with negatively charged particles accelerated from the cathode toward the anode, the charged polarity is likely to be reversed due to field electron emission from the particles due to the concentration effect of the electric field, and as a result, the proportion of particles that cannot collide with the anode surface is small. The amount of adhesion is relatively small, although it is thought that the amount of adhesion will increase. Therefore, it is more advantageous in terms of film formation efficiency to use the cathode side as the workpiece.

Hereinafter, one embodiment of the present invention will be explained in detail with reference to the drawings.

FIG. 2 shows, as an example, the main parts of the membrane manufacturing apparatus used in this example. A particle supply system P for supplying powder particles, which are the raw materials of the membrane, into a high electric field includes a diaphragm 8 having appropriately arranged pores for supplying particles, and a diaphragm 8 for loosely fastening and supporting the diaphragm to a powder filling container 7. It consists of a diaphragm holding ring 9, an elastic ring IO1 such as a rubber O-ring, an iron core 6 and a cylindrical electromagnetic coil 16 installed to cause the diaphragm to electromagnetically vibrate. A high voltage DC voltage is applied between this particle supply system and a workpiece 4 (flat plate shape) arranged to face the diaphragm by connecting the high voltage power supply 5 to the workpiece 4 with the former as the anode. In this figure, the diaphragm and the workpiece have electrode configurations corresponding to the anode and cathode shown in FIG. 1, respectively. To form the film, the diaphragm is electromagnetically vibrated by the action of an alternating magnetic field generated by an electromagnetic coil, and the powder particles 1 filled in the particle supply system are supplied between the electrodes through the pores of the diaphragm, and the method described above is performed. According to the principle, the adhesive film 3 is formed on the surface of the workpiece facing the diaphragm. Furthermore, the film formation is carried out in a vacuum container 12 evacuated to a high vacuum region by a vacuum pump 11 in order to prevent the charge amount of the particles from relaxing, improve the dielectric strength between the device components, and remove adsorbed gas. Ru.

In the example shown in the same figure, the diaphragm is used as an anode, but another flat anode is inserted and installed directly under the diaphragm, and the supply system is connected between this anode and the workpiece (cathode). Powder particles may also be provided. Furthermore, as a method other than the above-mentioned particle supply method using electromagnetic vibration, it is also possible to use a method in which a particle beam that is atomized by electrostatically charging powder particles flows between the anode and the workpiece. .

FIG. 3 shows an example of an apparatus for carrying out another method of the present invention, and parts corresponding to those in FIG. 2 are given the same reference numerals, and redundant explanation will be omitted. In this example, the workpiece that was also used as a cathode in the example of FIG. The deposited film 3 is formed by drawing out a powder particle beam through a hole on the cathode and irradiating the surface of the workpiece as a high-speed powder particle beam. The method shown in Figure 2 requires a conductive flat electrode to charge and accelerate the powder particles, so the workpiece is limited to those materials and shapes. Since the powder particle acceleration section and the film forming section are separated, restrictions on the workpiece are removed. That is, for example, the target workpiece may have a sharp protrusion shape, and the material may be a conductor, a semiconductor, or an insulator, so the range of application of film formation is expanded. Ru. Furthermore, it is also possible to perform controls such as electrostatic focusing and re-acceleration on the extracted accelerated powder particles.

As an example of the implementation of this film formation method, the applied voltage between the electrodes is 80
When carbon black particles with an average particle size of 0.024 μm are collided with the surface of a carbon tool full (SK3) under the formation conditions of kv, distance between poles 5 ■, and vacuum degree I x 10 Torr, the particle size corresponds to the particle size. A smooth and dense carbon film with a surface roughness in the microscopic range of 70A
It was confirmed that it could be produced at a formation rate of /min. This carbon film has good adhesion to the surface of the workpiece, so
Conventional carbon film forming methods such as vacuum evaporation, ionization evaporation, and ion beam evaporation have made it possible to form a thick film with a thickness of several micrometers, which has never been reported before. This advantage over conventional methods is due to the high velocity impact between the solids, which creates strong bonds between the particles and the workpiece material and between the particle materials. Note that the formation of this carbon film proceeds under conditions other than those described above, but when the applied voltage is 80 kV or more,
Since it is possible to obtain a sufficient speed to adhere even relatively large diameter particles in agglomerated state, such particles may be incorporated into the film, and the formed film material may lack structural homogeneity. There is.

Furthermore, if the applied voltage is extremely low, the speed will be insufficient for any deposition, and it goes without saying that film formation will not proceed.

Regarding the characteristics of the carbon film produced using this film formation method,
List the main items confirmed so far and their uses.

First of all, if we have knowledge about electrical properties, then regarding its uses: (a) The electrical resistivity at room temperature is measured to be 10Ω・Cl11, which is compared to that of raw carbon particles (to-6・cm order). A new thin-film semiconductor material with significantly higher resistance has been synthesized. Further, the conductivity type as a semiconductor was determined to be P type based on the measurement of thermoelectromotive voltage based on the Seebeck effect.

(b) The temperature dependence of resistivity is p, = Ae x P(B
/T)' (where ρC is resistivity, A and B are material constants, and T
It was confirmed that the measured temperature range was from 80 to 420 degrees Fahrenheit. Considering that this carbon film material has a small heat capacity because it is a thin film, and also has a high thermal conductivity as an inherent property of the carbon material, it can be applied to a thermistor element for temperature measurement with excellent responsiveness and reliability to temperature changes. is possible.

(c) The dependence of resistivity on electric field showed non-ohmic property in which the value of resistivity decreased significantly when a high electric field was applied.

That is, since a sudden increase in current occurs at this time, application to, for example, a varistor element for controlling a large current can be considered.

Furthermore, the characteristics when this carbon film, which is a P-type semiconductor, is formed on an n-type silicon semiconductor to configure a p-, n-junction diode are (d) current-voltage characteristics, such as a reverse bias voltage of a certain magnitude. There is a steep rise in current due to the Zener breakdown phenomenon. The characteristics of this p-n junction surface not only can be used as a constant voltage diode and a switching diode, but also suggests application to transistor elements.

(e) Generation of photovoltaic voltage was observed upon irradiation with incandescent light and sunlight, and the possibility of application to solar cells was discovered.

Next, regarding the knowledge regarding mechanical properties and its uses, (f) The hardness of this carbon film in the micro Vickers test was evaluated as I+ = 1100 to 1900, which is a significantly higher value than that of the raw material carbon. Indicated. Furthermore, in the sliding friction test, the coefficient of friction between the membrane materials was approximately 0.1. This is a fairly low value for solid-solid friction, and since the frictional atmosphere is constant regardless of whether it is in the air or in a high vacuum, it was found that it has good frictional properties.

Furthermore, it has been found that it exhibits excellent wear resistance against sliding wear caused by solid-solid friction and abrasive wear caused by scratching by hard abrasive grains. These findings suggest various applications in the mechanical industry as a hard protective film with lubricity, such as application to cutting tools for the purpose of improving cutting performance and extending tool life, or for improving wear resistance. Applications to various mechanical parts with sliding parts may be considered for the purpose of improvement.

The above examples demonstrate that the electrical and mechanical properties of films formed according to the present invention change significantly from those of the raw materials.

This change in properties may be considered to be due to local crystal structure conversion to a diamond structure caused by high-speed impact of carbon black particles.

As described above, according to the present invention, membrane materials with unique properties can be synthesized using relatively simple equipment and techniques.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and any raw material powder particles can be used as long as they have a fine diameter and are made of a material that exhibits conductivity in a high electric field.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the basic principle of the present invention, Figures 2 and 3 are cross-sectional diagrams of the membrane manufacturing apparatus used in the present invention, and Figure 4 is an explanatory diagram showing the agglomerated collective particles as a single powder between parallel plate electrodes. This is a table of experimental results showing separation into particles. l...Powder particles, 2...Charging accelerated powder particles, 3...
・44 Film deposition, 4... Workpiece, 5... High voltage power supply, 6... Iron core, 7... Powder filling container, 8... Vibration plate, 9... Vibrating temporary holding ring 10 ... Elastic ring, 11... Pump, 12... Vacuum container, 13...
Electrode, 14... Electrode, 15... Flat electrode, 16.
...Electromagnetic coil! 7... Powder particle younger brother 2 Figure 30 Western style of drawing (Contents 1: No change) Figure 1 Figure 4 Procedural amendment written style) % formula % 2. Name of the invention Method for producing solid thin film on processed surface 3. Person making the amendment Relationship to the case: Patent applicant Ide Tsutomu 1-67 Wakecho, Matsuyama City, Ehime Prefecture (3 others) 4. Agent 533 1-20-14 Higashinakajima, Higashiyodo Yo-ku, Osaka City No. Higashiro Station Building July 31, 1980 (Shipping date)

Claims (3)

[Claims] (1) Solid powder particles are electrostatically charged and accelerated in a high electric field applied in a vacuum to a high speed, and the particles are impacted and adhered to the surface of the workpiece to form a thin film. A method for producing a solid thin film on the surface of a workpiece. (2) A method for producing a solid thin film on the surface of a workpiece according to claim 1, which uses fine agglomerated particles separated by the action of an electric field as solid powder particles. (3) A method for producing a solid thin film on the surface of a workpiece according to claim 1, which utilizes single particles separated by the action of an electric field as solid powder particles. (i) The solid powder particles are electrostatically charged and accelerated by using parallel plate electrodes, and the particles in agglomerated state are reciprocated between the facing electrodes, thereby being charged and accelerated. The method for producing a solid thin film on the surface of a workpiece according to item 1, item 2, or item 3.