JPS63100364A - Apparatus for forming ultrafine powder film of oxide - Google Patents

Abstract

PURPOSE:To obtain a dry-tape fine powder film of oxide having high performance by controlling the temp. of a plasma jet with an induction heating coil and blowing a metallic or semiconductor material in the form of ultrafine powder-like vapor at a prescribed velocity or above to a substrate in a vacuum vessel to form an ultrafine powder film thereon. CONSTITUTION:The metal or semiconductor which is melted by heating to generate the ultrafine powder-like vapor is disposed in a vacuum vapor chamber 1 and the plasma jet is blown thereto. The induction heating coil 6 is provided at the blow port to control the temp. of the plasma jet. The ultrafine particles of the metal or semiconductor are transferred from the vapor chamber 1 to a film forming chamber 2 of a lower pressure through a transfer pipe 7. A high-frequency coil is provided on the outside of the transfer pipe 7 to convert the oxygen supplied from an oxygen introducing pipeline 13 to the plasma. The oxidized vapor is bombarded at the prescribed velocity or above to the substrate 11 in the film forming chamber 2, by which the ultrafine powder film is formed thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to an apparatus for producing ultrafine metal or semiconductor oxide powder films used in gas sensors and the like.

(Prior art and its problems) Ultrafine powder films of metal oxides or semiconductor oxides have been developed in recent years.
They are attracting attention as new functional materials such as new materials and gas sensors, and most of them are made using wet methods such as the alkoxide method, which liberates metal or semiconductor oxides or hydroxides from organic metals in solution. . However, depending on the purpose of use, ultrafine powder produced by such a wet method requires processing such as washing, drying, and kneading to mix it with a binder before applying it to a sheet, which takes a lot of time and energy. It was necessary. In order to solve such problems, for example, as shown in Japanese Patent Publication No. 59-43988,
Dry production of ultrafine powder and film formation methods have been proposed. but,
Although this method solves the above-mentioned problems, (1) it is not suitable for high melting point materials because it uses resistance heating to vaporize the metal; (2) it is not suitable for high melting point materials;
A high-frequency coil for generating plasma is placed inside the vacuum container in which the raw metal is placed, so it becomes plasma inside the high-frequency coil and combines with the vapor of the metal or semiconductor to form oxides and nitrides of the metal or semiconductor. The raw material gas that creates substances and carbides is turned into plasma even outside the coil, consuming excess power. (3) The evaporated ultrafine metal or semiconductor powder adheres to the high-frequency coil, and as a result, the function of the high-frequency coil is impaired. (4) The high-frequency coil for generating plasma is housed in a vacuum container, which increases the vacuum volume and requires large vacuum equipment; (5) Metal or semiconductor particles generated by heating and melting Only a few percent of the steam is used for film formation, and the remaining steam is wasted (
6) There were problems such as weak adhesion between the ultrafine powder particles and the substrate surface.

(Purpose of the invention) This invention was made in view of the above-mentioned problems, and it is easy to apply rain to high melting point materials, is small, has high performance, and has strong adhesion of the ultrafine powder film to the substrate. The purpose of the present invention is to provide a dry type oxide ultrafine powder film generation device.

(Summary of the Invention) The present invention is an apparatus that heats and evaporates a metal or semiconductor in a vacuum, liquefies the metal or semiconductor vapor, and forms an ultrafine oxide powder film on a substrate. In addition to using a plasma jet device that can easily obtain a temperature for heating and melting metals or semiconductors in a vacuum,
1) When the vapor made of the ultrafine powder obtained by heating and melting collides with the substrate surface at a predetermined speed or higher, an ultrafine powder film with strong adhesion is formed on the substrate; (2) the plasma jet Since the diameter is usually small and the temperature distribution over the cross section is uneven, the evaporation rate of the vapor evaporated from the metal or semiconductor irradiated by the plasma jet varies depending on the position on the plasma cross section and is uniform over the entire cross section. However, if an induction heating coil is installed at the outlet of the plasma jet and a high-frequency current is supplied, since the plasma jet is a conductor, it will be heated by the high-frequency coil and create a plasma with a large diameter and uniform temperature distribution. Focusing on the fact that it becomes a jet and makes it possible to form an oxide ultrafine powder film with a uniform primary particle size, we developed a first vacuum container in which a metal or semiconductor that is heated and melted to generate ultrafine powder vapor is arranged. a plasma jet device that heats and melts a metal or semiconductor placed in the vacuum container, which is equipped with an induction heating coil for controlling the temperature of the plasma jet at the outlet from which the plasma jet is blown; a second vacuum container, which is provided with a substrate on which a film of oxidized ultrafine powder is formed and a mounting table on which the substrate is placed, and whose interior is maintained at a lower pressure than the first vacuum container; and vapor of metal or semiconductor generated by heating and melting in the first vacuum container by a plasma jet from the plasma jet device. A transfer pipe line for transferring oxygen to the second vacuum container due to the pressure difference between the second vacuum containers and an oxygen introduction pipe line for introducing oxygen into the pipe line; a plasma oxidizing section equipped with a high-frequency coil that converts oxygen introduced into the pipe into plasma; and a nozzle for causing the vapor oxidized in the plasma meltening section to collide with the substrate at a predetermined speed or higher. By configuring the production equipment using The aim is to obtain a manufacturing device that can form

(Embodiment of the Invention) FIG. 1 shows an embodiment of a metal or semiconductor oxide ultrafine powder film manufacturing apparatus constructed according to the present invention. This device consists of an evaporation chamber 1, which is a first vacuum container, containing a raw material 5 made of metal or semiconductor that is heated and melted to generate ultrafine powder vapor, and a plasma jet at an outlet from which a plasma jet is blown. The evaporation chamber 1 is equipped with an induction heating coil 6 which is arranged to surround the jet and which increases the temperature of the plasma jet by inductively heating the plasma jet by supplying a high-frequency current and uniformizes the temperature distribution in its cross section. a plasma jet device 3 for heating and melting the raw material 5; a substrate 11 on which a film of ultrafine powder is formed by oxidizing the steam generated by heating and melting the raw material 5 by a method described in detail below; a film-forming chamber 2 which is a second vacuum chamber in which a water-cooled rotary table 12 on which a substrate is placed is arranged, and the pressure inside the chamber is maintained at a lower pressure than that in the evaporation chamber 1;
This forms a transfer pipe 7 that transfers the vapor generated from the raw material 5 in the evaporation chamber 1 to the film formation chamber 2 due to the pressure difference between the evaporation chamber 1 and the film formation chamber 2, and also supplies oxygen to this pipe 7. A high-frequency coil 8 that is wound around the outer circumference of the transfer pipe 7 and activates the oxygen introduced into the pipe to convert it into plasma and efficiently oxidizes the vapor. An oxidizing section 20 and a nozzle formed at the tip of the transfer pipe 7 constituting the plasma oxidizing section for causing the vapor oxidized in the plasma oxidizing section 20 to collide with the surface of the substrate 11 at a predetermined speed or higher. An ultrafine oxide powder film is formed on the substrate through the following process.

The raw material 5 is put into the adiabatic ceramic port 4 for holding the raw material metal or semiconductor in the evaporation chamber 1, the evaporation chamber 1 and the film forming chamber 2 are evacuated, and the film forming chamber 2 is separated from the evaporation chamber 1 by 1.
The pressure should be ~2 orders of magnitude lower.

Furthermore, the raw material 5 is irradiated with a plasma jet from the plasma jet device 3 using an inert gas such as Ar or He, a reducing gas such as H2, or a mixed gas of these inert gases and a reducing gas as the plasma raw material gas. At the same time, by heating the plasma jet by supplying an alternating current of 11,300 kHz to the induction heating coil, the temperature distribution in the cross section of the plasma jet is made uniform, the raw material 5 is heated and melted, and the raw material 5 is turned into particles in the form of ultra-fine powder. Generates steam with uniform diameter. In this case, the power source for generating the plasma jet is a DC power source, that is, the plasma jet device is used as a DC torch to prevent pulsations in the plasma current and, therefore, in vapor generation, thereby achieving more uniform film formation. The vapor thus generated flows from the evaporation chamber 1 side to the film formation chamber 2 side through the quartz tube 7 together with the source gas of the plasma due to the pressure difference between the evaporation chamber 1 and the film formation chamber 2 . Oxygen gas is introduced into the steam from the oxygen introduction pipe 13 in the middle of the quartz tube 7 and mixed with the steam, and when a high frequency voltage such as 13.56 MHz is applied to the high frequency coil, the transfer pipe 7 is A high frequency plasma is formed in the constituent quartz tube to oxidize the vapor. The steam oxidized by this high-frequency plasma becomes a jet stream at a speed higher than a predetermined speed through a nozzle 9 formed at the tip of the transfer pipe, and collides and deposits on the substrate 11 placed on the water-cooled rotary table 12. to form a highly adhesive ultrafine powder film on the substrate. The reason why the mounting table on which the substrate 11 is placed is a water-cooled rotary table is as follows. That is, by cooling the substrate with water, (1) it is possible to prevent uneven film thickness, (2) it is possible to prevent variations in particle size, and (3) the growth rate of i can be reduced. It can be done quickly. If the substrate is not cooled, the growth rate of the film will be slow and the oxidized ultrafine powder will escape without being formed into a film, reducing the film formation efficiency. Next, by using a rotating table, even if the flame of oxidized steam ejected from the nozzle flickers on the substrate surface, the table can be rotated and moved in a straight line within the surface of the table. It becomes possible to obtain uniform film formation on the substrate.

In order to more accurately control the film thickness of the ultrafine powder film obtained in this way, a shutter 1o shown in Fig. 1 is used, but if the purpose is only to control the film thickness, this shutter is usually omitted. Good too. However, if this shutter could be used to prevent vapor from colliding with the substrate surface at any time, after film formation was completed on multiple substrates placed on a rotary table, unformed films placed on another rotary table could be This has the advantage that films can be easily formed on multiple substrates, that is, batch processing can be easily performed.

When the ultrafine oxide particle film produced with this apparatus was observed with a scanning electron microscope, it was found to be a film with a uniform primary particle diameter of 100 to 150A.

(Effects of the Invention) As described above, according to the present invention, since a plasma jet is used as a heat source to heat and evaporate raw material metal or semiconductor, ultrafine powder film of oxide of metal or semiconductor material with high melting point is formed. Can be easily formed. Further, according to the manufacturing apparatus of the present invention, an induction heating coil is arranged at the outlet of the plasma jet, and a high frequency current is supplied to this coil to heat the plasma jet, thereby controlling the temperature distribution on the cross section of the plasma jet. Since the irradiation is made uniform, the evaporation rate of the metal or semiconductor material from the irradiated area can be kept constant, and an ultrafine oxide powder film with uniform primary particle diameter can be formed on the substrate. Furthermore, both the metal or semiconductor vapor that has been heated and evaporated and the oxygen-containing gas that has been turned into plasma and combined with the metal or semiconductor vapor are only present inside the transfer pipe of the plasma oxidation section. In addition, there is also a gas outside the plasma chamber that is combined with the metal or semiconductor vapor, which prevents this gas from turning into plasma and causing unnecessary power consumption. Furthermore, although the cause is unknown, when ultrafine particles collide with the substrate surface at a speed higher than a certain speed, a considerably large adhesion force is generated between the ultrafine particles and the substrate surface. The manufacturing apparatus of the present invention focuses on this point, and by providing a nozzle section between the transfer pipe and the substrate, the ultrafine particles are made to collide with the substrate surface at high speed, so that they have a strong adhesion force to the substrate. , it has become possible to obtain ultrafine particle films of metal or semiconductor oxides.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an embodiment of an ultrafine oxide powder film manufacturing apparatus constructed based on the present invention. 1: Evaporation chamber (first vacuum container), 2: Film forming chamber (second vacuum container), 3: Plasma jet device, 5: Raw material (metal or semiconductor), 6: Induction heating coil, 7: Quartz￥ F(
transfer pipe), 8: high frequency coil, 9: nozzle, 10: shutter, 11: substrate, 12: rotary table (mounting table),
13: Arrangement introduction pipe, 20: Plasma oxidation section.

Claims (1)

[Scope of Claims] 1) A first vacuum container in which a metal or semiconductor that is heated and melted to generate ultrafine powder vapor is placed, and a plasma jet temperature is controlled between a first vacuum container in which a metal or semiconductor that is heated and melted generates ultrafine powder vapor, and an outlet through which the plasma jet is blown out. A plasma jet device is equipped with an induction heating coil to heat and melt the metal or semiconductor placed in the vacuum container, and a film of ultrafine powder is formed on the surface by oxidizing the vapor of the metal or semiconductor. a second vacuum container in which a substrate and a mounting table on which the substrate is placed are arranged, and the inside of the container is maintained at a lower pressure than the first vacuum container; and the plasma jet in the first vacuum container. The metal or semiconductor vapor generated by heating and melting by the plasma jet from the device is transferred to the second vacuum vessel by the pressure difference between the first and second vacuum vessels.
an oxygen introduction pipe for introducing oxygen into the vacuum container; and an oxygen introducing pipe for introducing oxygen into the pipe; an oxide ultrafine powder characterized by comprising: a plasma oxidation section equipped with a high frequency coil for oxidizing the substrate; and a nozzle for causing vapor oxidized in the plasma oxidation section to collide with the substrate at a predetermined speed or higher. Membrane manufacturing equipment. 2) In the apparatus set forth in claim 1, the plasma jet device for heating and melting metals or semiconductors uses an inert gas such as Ar or He, a reducing gas such as H_2, or the inert gas. An apparatus for producing an ultrafine oxide powder film, characterized in that it is a direct current torch that uses a gas mixture with a reducing gas as a raw material gas for plasma, and converts this raw material gas into plasma using a direct current voltage. 3) The apparatus according to claim 1, wherein the mounting table on which the substrate on which the ultrafine oxide powder film is formed is equipped with a cooling mechanism for cooling the substrate. A manufacturing device for ultrafine oxide powder film. 4) In the apparatus according to claim 1, the mounting table on which the substrate on which the ultrafine oxide powder film is formed is mounted with a plurality of substrates facing perpendicularly to the nozzle in the circumferential direction. 1. An apparatus for producing an ultrafine oxide powder film, comprising a rotary table that can rotate around an axis, and the table is movable in a straight line within the plane of the table. 5) In the apparatus set forth in claim 1, the second vacuum vessel in which the substrate on which the ultrafine oxide powder film is formed is disposed is arranged such that the oxidized vapor is directed to the substrate on the nozzle side of the substrate. An apparatus for producing an ultrafine oxide powder film, characterized in that it is equipped with a shutter for preventing collision.