JP2007077447A - Composite structure, and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite structure very reduced in microgaps from which gas is gradually emitted. <P>SOLUTION: The composite structure 10 comprises: a base material 11 made of metal, ceramic, resin or a composite material thereof; a structure 12 made of a brittle material formed on the surface thereof by an aerosol deposition process; and a thin film 13 of one or more kinds selected from transition metal carbides, transition metal nitrides, transition metal borides and diamond like carbon and formed on the surface thereof. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a composite structure having a multilayer structure in which a brittle material structure and a film made of one or more of transition metal carbide, transition metal nitride, transition metal boride, and diamond-like carbon are formed on the surface of a substrate. It relates to the manufacturing method.

  As a method for forming a brittle material structure on the surface of a substrate without a heating step, a technique called an aerosol deposition method has been recognized.

  This aerosol deposition method is described in detail in Patent Document 1. That is, an aerosol in which fine particles of a brittle material or the like are dispersed in a gas is jetted from a nozzle toward the base material, and the fine particles collide with a base material such as metal, glass, ceramics, or plastic. It is characterized in that the fine particles are deformed and crushed and joined together to directly form the structure made up of the constituent materials of the fine particles on the base material. Especially, the structure is formed at room temperature that does not require heating means. It is possible to obtain a structure having mechanical strength equivalent to that of the fired body.

  Also, a manufacturing method in which ultrafine particles such as ceramics having a particle size in the range of 10 nm to 5 μm are dispersed in a gas to form an aerosol, and then sprayed toward the substrate as a high-speed ultrafine particle flow from a nozzle to form a deposit. Is disclosed in Patent Document 2. In Patent Document 2, the substrate is irradiated with high-energy atoms such as ions, atoms, molecular beams, and low-temperature plasma to make the structure to be made strong.

  The apparatus used for the aerosol deposition method basically comprises an aerosol generator for generating aerosol and a nozzle for injecting the aerosol toward the substrate, and produces a structure with an area larger than the opening of the nozzle. In some cases, it has a position control means that moves and swings the base material and the nozzle relative to each other, and in the case of manufacturing under reduced pressure, it has a chamber for forming the structure and a vacuum pump, and generates aerosol. It is common to have a gas generation source for generating the gas.

  The process temperature of the aerosol deposition method is room temperature, and one feature is that the structure is formed at a temperature sufficiently lower than the melting point of the particulate material, that is, several hundred degrees C. or less.

  The fine particles used are mainly brittle materials such as ceramics and semiconductors, and fine particles of the same material can be used singly or mixed, and different kinds of fine particles of brittle material can be mixed or used in combination. Is possible. It is also possible to partially use a metal material, an organic material, or the like mixed with the brittle material fine particles or coat the surface of the brittle material fine particles. Even in these cases, the main component of structure formation is a brittle material.

  In the structure formed by the aerosol deposition method, when crystalline brittle material fine particles are used as a raw material, the brittle material portion of the structure is a polycrystalline body whose crystallite size is smaller than that of the raw material fine particles. In many cases, the crystal has substantially no crystal orientation, and it can be said that there is substantially no grain boundary layer composed of a glass layer at the interface between brittle material crystals. There is a feature that an anchor layer is often formed to penetrate.

  In addition, the structure formed by the aerosol deposition method is clearly different from the so-called green compact in which the fine particles are packed together by pressure and keeps the form by physical adhesion. Yes. In addition, in the formation of the structure, the brittle material fine particles are crushed and deformed by measuring the brittle material fine particles used as a raw material and the crystallite size of the formed brittle material structure by an X-ray diffraction method. I can judge. That is, the crystallite size of the structure formed by the aerosol deposition method is smaller than the crystallite size of the raw material fine particles. A new surface in which atoms originally present inside and bonded to other atoms are exposed is formed on the slip surface or fracture surface formed by crushing or deforming fine particles. This active new surface having a high surface energy is considered to be formed by joining the surface of the adjacent brittle material, the new surface of the adjacent brittle material, or the substrate surface. In addition, when hydroxyl groups are present on the surface of the fine particles moderately, a mechanochemical acid-base dehydration reaction occurs due to local shear stress generated between the fine particles or between the fine particles and the structure when the fine particles collide with each other. It can be considered. The addition of continuous mechanical impact force from the outside causes these phenomena to occur continuously, and the progress and densification of joints are performed by repeated deformation and crushing of fine particles, and brittle material structures grow. it is conceivable that.

Japanese Patent No. 3348154 JP 2000-212766 A

  Conventionally, many proposals have been made on composite structures in which structures composed of components mainly composed of brittle materials are formed on various substrates by an aerosol deposition method. Since the aerosol deposition structure is formed on a substrate with a formation height of several tens of μm, and in some cases up to several hundreds of μm, for example, an insulating film used for applications where a high voltage of several kV or more is applied. It is conceivable to use a dielectric film for a circuit board that utilizes the dielectric properties of the material.

The aerosol deposition method is formed by colliding the fine particles of brittle material on the base material and bonding and depositing the constituent materials of the fine particles by crushing and deforming the fine particles. Formation of a dense structure having a resistance of 10 ¹⁴ Ω · cm or more is achieved. Or it may become a porous structure with a minute gap depending on the forming conditions, and the volume resistivity in the room temperature atmosphere may be lower than this. The reason for this is that, depending on the state of crushing and deformation, there are minute gaps between the structural elements that were originally fine particles, and gas components and water vapor components enter the gaps and adhere to the surface. It is considered that the resistance value is decreased by moving at the time of application. Depending on the situation such as the formation of continuous pores, the resistivity value may decrease to about 10 ⁸ Ω · cm. The minute gap here is a gap of about several to several tens of nanometers that is finally observed, for example, with a transmission electron microscope. Furthermore, it is possible to form a structure having a large pore inside or a porous body having continuous pores.

  On the other hand, in the aerosol deposition method, the internal stress of the structure is generally smaller when forming a porous structure with a minute gap than when forming a dense body with high resistivity. There are advantages such that the formation speed is high, the formation height can be increased, or the apparent dielectric constant can be reduced. An increase in the formation height is advantageous because it contributes to an improvement in the breakdown voltage value. In addition, when using characteristics such as thermal radiation characteristics (radiation characteristics) and heat shielding characteristics, the structure formation thickness is greatly involved, but the fine structure is not involved. Is advantageous.

  However, we try to use structures formed by the aerosol deposition method for insulation and dielectric functions in equipment used in vacuum environments and parts used in corrosive environments such as gas and plasma. In the case of a structure having a minute gap, in a vacuum application, the gas gradually released from the minute gap does not increase the degree of vacuum in the device forever, or water vapor that should be avoided is released. When used in a malfunction or corrosion-resistant environment, there is a problem that gas enters from a minute gap and corrosion is likely to proceed due to the large specific surface area of the structure.

  In addition, the aerosol deposition method is characterized by forming a structure by crushing / deformation, and the crystal level is as small as several to several tens of nanometers. When a structure having a fine gap is used, the corrosion resistance may be inferior to a fired body made of the same material.

  On the other hand, a ceramic film formed by PVD, CVD, or sol-gel is easy to obtain a dense material, but it is difficult to form a thick structure, and in the case of a thin film, it is affected by the surface roughness of the base material. There are problems such as having minute defects.

In order to solve the above problems, a composite structure according to the present invention has a structure made of a brittle material on the surface of a base material, and transition metal carbide, transition metal nitride, transition metal boride, diamond on the surface of the structure. A film composed of one or more of like carbon is formed, and the structure is a polycrystalline structure formed by injecting and colliding an aerosol in which fine particles of a brittle material are dispersed in a gas onto the substrate surface. The grain boundary layer made of a glass layer is not substantially present at the interface between the crystals.
By applying the aerosol deposition method, a part of the structure becomes an anchor portion that bites into the substrate surface.

  By obtaining a structure with such a structure, for example, a thick brittle material structure can be used to exhibit pore sealing of the base material, large dielectric breakdown characteristics, thermal radiation characteristics, thermal insulation characteristics, low dielectric constant characteristics, etc. By forming a dense film on the surface, it becomes possible to develop gas barrier properties, corrosion resistance, and the like.

  For example, application to a ceramic member for vacuum equipment is specifically mentioned. This is because a ceramic fired body is used as the substrate, but the fired body has a large surface area due to the presence of fine irregularities and pores on the surface, and the amount of gas components adsorbed on the surface is large. However, there is a problem that the time to reach the desired degree of vacuum is prolonged and the process speed is lowered, but the surface of this ceramic fired body is made flat by forming a brittle material structure by the aerosol deposition method. Among transition metal carbides, transition metal nitrides, transition metal borides, and diamond-like carbons, including titanium carbide, which is known to have a low specific surface area and high water repellency and low gas adsorption capacity. A good ceramic member for vacuum equipment can be obtained by forming a film composed of one or more of the above. In this case, a film made of one or more of transition metal carbide, transition metal nitride, transition metal boride, and diamond-like carbon can be a thin film of 1 μm or less.

  A brittle material structure manufactured by the aerosol deposition method is easy to form a thick film of several μm or more, and mainly has a surface flatness of the substrate. It may be present and this fine gap can be covered with a thin film. Even if a thin film formed directly by PVD, CVD, sol-gel method, etc. is formed on the substrate, the thin film only grows according to the unevenness of the substrate, and the surface roughness does not decrease or the specific surface area decreases. In addition, it is conceivable that a defective portion of the film remains due to its complicated shape, but according to the present invention, there is no such disadvantage.

  Here, the transition metal carbide is titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, niobium carbide, tantalum carbide, chromium carbide, molybdenum carbide, tungsten carbide, etc., and the transition metal nitride is titanium nitride, nitride Zirconium, hafnium nitride, vanadium nitride, niobium nitride, tantalum nitride, chromium nitride, molybdenum nitride, etc., and transition metal borides include titanium boride, zirconium boride, hafnium boride, vanadium boride, niobium boride, Examples include tantalum boride, chromium boride, molybdenum boride, and tungsten boride. As the thin film material, for example, titanium nitride or titanium carbide, which is said to have a low gas adsorption density, may be selected. However, it is conceivable to use a material that is a material having a low gas adsorption property even with other materials. Also, a mixture or a solid solution of these may be used, and those mainly incorporating various elements may be used. The diamond-like carbon may be mainly doped with nitrogen or the like. In view of the characteristics utilizing the surface function, a thin film-like body having a film thickness of 0.1 μm or more and less than 5 μm, or even 1 μm or less is sufficient.

  In the method of manufacturing a composite structure in the present invention, an aerosol in which fine particles of a brittle material are dispersed in a gas is sprayed toward the surface of the base material to form a structure of the brittle material as a constituent material of the fine particles on the base material surface. After this step, a film made of one or more of transition metal carbide, transition metal nitride, transition metal boride, and diamond-like carbon is formed on the surface of the structure by any one of PVD, CVD, and sol-gel methods. Form.

  Examples of the PVD method include a vacuum deposition method, a sputtering method, an electron beam deposition method, a molecular beam epitaxy method, and a laser ablation method. Examples of the CVD method include a thermal CVD method, an MOCVD method, a plasma CVD method, and a laser CVD method. Etc.

Here, the terms used in this specification will be described below.
(Fine particles)
When the primary particles are dense particles, the average particle size identified by particle size distribution measurement or a scanning electron microscope is 10 μm or less. In addition, when the primary particles are porous particles that are easily crushed by impact, the average particle diameter is 50 μm or less.
(aerosol)
The above-mentioned fine particles are dispersed in a gas such as helium, nitrogen, argon, oxygen, dry air, or a mixed gas thereof, and it is desirable that the primary particles are dispersed. Usually, the primary particles are aggregated. Containing aggregated grains. The gas pressure and temperature of the aerosol are arbitrary, but the concentration of fine particles in the gas is from 0.0003 mL / L to 0 at the time of injection from the nozzle when the gas pressure is converted to 1 atm and the temperature is converted to 20 ° C. It is desirable for structure formation to be in the range of 0.06 mL / L.
(Polycrystalline)
In this case, it refers to a structure in which crystallites are joined and integrated. The crystallite is essentially one crystal, and its diameter is usually 5 nm or more. However, the case where the fine particles are taken into the structure without being crushed rarely occurs, but is substantially polycrystalline.

  According to the aerosol deposition method, a film having a relatively large thickness can be formed in a short time, but the crystal level is as small as several to several tens of nanometers, and in some cases has a minute gap, In this case, the gas release time in vacuum is long, and the corrosion resistance is poor. However, as in the present invention, a film made of one or more of transition metal carbide, transition metal nitride, transition metal boride and diamond-like carbon is formed on the surface by any of PVD, CVD, and sol-gel methods. If formed, it is advantageous in terms of various functions such as vacuum environment characteristics and corrosion resistance.

  FIG. 1 is a cross-sectional view of a composite structure according to the present invention. A composite structure 10 includes a base material 11 made of metal, ceramics, resin, or a composite material thereof, and an aerosol deposition method on the surface. It consists of a structure 12 made of a brittle material and a thin film 13 made of one or more of transition metal carbide, transition metal nitride, transition metal boride and diamond-like carbon formed on the surface.

  The shape and structure of the base material 11 are arbitrary, and the formation position, formation area, and formation pattern of the structure 12 and the thin film 13 formed on the surface are also arbitrary. These need only be formed on the necessary portions.

  FIG. 2 shows an example of the aerosol deposition apparatus 20. An aerosol generator 203 is installed at the tip of a nitrogen gas cylinder 201 via a gas transport pipe 202, and an aerosol transport pipe 204 having a diameter of 2 mm, for example, is provided downstream thereof. For example, a nozzle 206 having an introduction opening having a diameter of 2 mm and a lead-out opening having a diameter of 10 mm × 0.4 mm is disposed in the structure forming chamber 205. The aerosol generator 203 is filled with brittle material fine particles, for example, aluminum oxide fine particle powder. A base material 208 held by an XY stage 207 is disposed at the tip of the opening of the nozzle 206. The structure forming chamber 205 is connected to a vacuum pump 209. For the base material 208, the composite material as described above is employed.

  The operation of the aerosol deposition apparatus 20 will be described below. The nitrogen gas cylinder 201 is opened, gas is fed into the aerosol generator 203 through the gas transport pipe 202, and at the same time, the aerosol generator 203 is operated to generate an aerosol in which brittle material fine particles and nitrogen gas are mixed in an appropriate ratio. Further, the vacuum pump 209 is operated to generate a differential pressure between the aerosol generator 203 and the structure forming chamber 205. The aerosol rides on this differential pressure, is introduced into the aerosol transport pipe 204 on the downstream side, accelerates, and is sprayed from the nozzle 206 toward the substrate 208. The base material 208 is swung in two axes by the XY stage 207, and a film-like brittle material structure is formed on the base material 208 by collision of fine particles while changing the aerosol collision position.

  FIG. 3 is a partial cross-sectional structural schematic diagram of an example in which the composite structure according to the present invention is applied as a ceramic member for vacuum equipment. The ceramic member for vacuum equipment corresponds to a wall member of a vacuum chamber, a stage having an actuator function, a peripheral member such as an electrostatic chuck, or a fixed member.

  In the surface portion cross section of the ceramic member 30 for vacuum equipment, a brittle material structure 32 is formed on an alumina fired body 31 as a base, and a titanium carbide film 33 is coated on the surface. Here, the alumina fired body 31 often has pores inside, but this is omitted in the drawing and only the portion close to the surface is represented. The alumina fired body is, for example, a structure having an aluminum oxide purity of 80 to 96%, and has numerous pores having a size of several hundred nm to several tens of μm on the surface depending on the raw material powder particle size and the firing method. Therefore, the surface area which becomes the adsorption site of the gas component is increased. Therefore, an aluminum oxide structure is formed on the surface by an aerosol deposition method with a film thickness of 5 μm or more and less than 50 μm according to the size of the pores. Thereby, the pores of the alumina fired body 31 can be completely sealed, and the surface area can be minimized by polishing the surface. A dense titanium carbide having low gas adsorption characteristics is formed on this surface as a thin film of, for example, several hundred nm by the CVD method. With such a composite structure, a ceramic member for vacuum equipment having an improved degassing rate in a vacuum can be obtained.

Sectional view of the composite structure according to the present invention Diagram showing an example of an aerosol deposition device Sectional drawing of the ceramic member for vacuum equipment as a composite structure which concerns on this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Composite structure, 11 ... Base material, 12 ... Structure, 13 ... Transition metal carbide, Transition metal nitride, Transition metal boride, Diamond-like carbon thin film.
DESCRIPTION OF SYMBOLS 20 ... Aerosol deposition apparatus, 201 ... Nitrogen gas cylinder, 202 ... Gas conveyance pipe, 203 ... Aerosol generator, 204 ... Aerosol conveyance pipe, 205 ... Structure formation chamber, 206 ... Nozzle, 207 ... XY stage, 208 ... Base material 209: Vacuum pump.
30 ... Ceramic member for vacuum equipment, 31 ... Alumina fired body, 32 ... Brittle material structure, 33 ... Titanium carbide film.

Claims (4)

A composite in which a structure made of a brittle material is formed on the surface of the substrate, and a film made of one or more of transition metal carbide, transition metal nitride, transition metal boride and diamond-like carbon is formed on the surface of the structure The structure is a polycrystalline structure formed by injecting and colliding an aerosol, in which fine particles of a brittle material are dispersed in a gas, onto the surface of the base material, and is formed at the interface between the crystals. Is a composite structure characterized in that there is substantially no grain boundary layer composed of a glass layer. 2. The composite structure according to claim 1, wherein a part of the structure includes an anchor portion that bites into the surface of the base material. 3. The composite structure according to claim 1, wherein a film made of at least one of the transition metal carbide, transition metal nitride, transition metal boride, and diamond-like carbon is formed by a PVD method, a CVD method, or a sol-gel method. A composite structure, wherein the structure is formed by an aerosol deposition method. An aerosol in which fine particles of a brittle material are dispersed in a gas is sprayed toward the surface of the base material to form a polycrystalline structure of the brittle material, which is a constituent material of the fine particles, on the surface of the base material. And a method of forming a film made of one or more of transition metal carbide, transition metal nitride, transition metal boride, and diamond-like carbon on the surface of the structure by any one of the method and the sol-gel method. A method for producing a composite structure, comprising obtaining the composite structure according to claim 3.