JP2005344171A - Raw material powder for film deposition, and film deposition method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide raw material powder which is less liable to aggregate even in a film deposition step by an AD (aerosol deposition) method for a long time. <P>SOLUTION: Raw material powder is used for a film deposition method in which composition material of raw material powder is deposited on a substrate by spraying raw material powder toward the substrate, and contains base particles 11, and fine particles 12 which have the grain size smaller than that of the base particles 11 and are deposited to cover the surface of the base particles 11. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aerosol deposition (AD) method in which a raw material composition material is deposited on a substrate by spraying the raw material toward the substrate, and a raw material powder used in the AD method.

  The aerosol deposition (AD) method is a film forming method in which an aerosol containing raw material powder (raw material powder) is generated, and the raw material is deposited by spraying it from a nozzle toward a substrate. Here, the aerosol refers to solid or liquid fine particles suspended in a gas. In the AD method, the raw material powder sprayed at a high speed collides with the lower layer such as the substrate or the previously formed deposit, and the crushing surface generated by crushing the powder at the time of the collision is in the lower layer. The film is formed by the adhering mechanochemical reaction. By using such an AD method, a dense and strong thick film that does not contain impurities can be formed. Therefore, for example, it is expected that the performance of these devices can be improved by forming a piezoelectric film used for a piezoelectric actuator, a piezoelectric pump, an ink jet printer head, an ultrasonic transducer and the like by the AD method. The AD method is also called a jet deposition method or a gas deposition method.

  FIG. 5 is a schematic diagram showing how aerosol is generated. As shown in FIG. 5, the aerosol is generated in the aerosol generation chamber 101 in which the fine powder 100 of the raw material is arranged. In the aerosol generation chamber 101, a winding nozzle 102 and a pressure adjusting nozzle 103 for introducing a carrier gas, and an aerosol outlet pipe 104 for leading the generated aerosol are arranged. The winding nozzle 102 is disposed so as to blow up carrier gas from the vicinity of the bottom of the aerosol generation chamber 101, whereby the raw material powder 100 is rolled up and aerosol is generated. The pressure adjustment nozzle 103 is provided to control the spray pressure of the aerosol by adjusting the pressure in the aerosol generation chamber 101. The aerosol lead-out tube 104 is connected to an aerosol injection nozzle disposed in the film forming chamber, and supplies the generated aerosol to the injection nozzle. Such an aerosol generation chamber 101 is installed on a vibration table 105. The vibration table 105 gives minute vibrations to the aerosol generation chamber 101, thereby giving kinetic energy for floating to the raw material powder 100, and in the vicinity of the carrier gas outlet of the winding nozzle 102. Of powder 100 are supplied one after another.

  By the way, if the generation of the aerosol is continued, the raw material powder aggregates over time due to van der Waals force, liquid bridging force, electrostatic force, etc. acting between adjacent particles, and aggregated particles are formed. . Further, a cyclone is generated in the aerosol generation chamber 101 by the carrier gas injected from the pressure adjusting nozzle 103, so that particles having a large particle size among the rolled up raw material powder are caused by centrifugal force. After being classified, it collides with the wall of the aerosol generation chamber 101 and falls. While such a phenomenon is repeated, the particles are charged by friction and become larger (for example, several μm to several mm in diameter).

  Generation | occurrence | production of such an aggregated particle is an obstacle at the time of forming a high quality AD film (film | membrane formed by AD method). That is, huge particles among the aggregated particles accumulate at the bottom of the aerosol generation chamber, so that the aerosol cannot be generated stably and the aerosol concentration supplied to the injection nozzle cannot be kept uniform. . For this reason, the film forming speed decreases and the film thickness becomes uneven, making it difficult to form a large area film or a thick film. Further, when the aggregated particles are mixed in the aerosol, the aggregated particles not only contribute to the film formation but also blast the film formed in the opposite direction. For this reason, defects are increased in the formed film, which causes problems in improving the function of the film and durability over time.

  As a related technology, Patent Document 1 discloses that the amount of water contained in the brittle material particle powder of the raw material is 0.45% or less or 0.4% or less, thereby reducing the aggregation of the raw material powder, and the aerosol. It is disclosed to stabilize the supply amount. By using such brittle material particles, aggregation due to the liquid crosslinking force can be suppressed. However, if film formation is continued for a long time, charging due to friction between the raw material powders increases, and thus aggregation cannot be prevented.

  In Patent Document 2, an aerosol in which fine particles are dispersed in a gas is sprayed from the tip of a nozzle and sprayed onto the substrate to form a structure made of the material of the fine particles on the substrate, thereby forming a composite structure consisting of the substrate and the structure. In the composite structure manufacturing method for manufacturing the above, it is disclosed that at least when the aerosol is sprayed on the substrate, the temperature at the nozzle tip is controlled by a heating means so as to be 50 ° C to 150 ° C. Further, in Patent Document 3, in the above composite structure manufacturing method, at least when aerosol is sprayed onto a substrate, the temperature of the aerosol transport pipe and the temperature of the nozzle are 50 ° C. to 150 ° C., and the temperature of the nozzle is It is disclosed that the temperature of the aerosol transport pipe is controlled so that the temperature of the entire inner wall of the aerosol transport pipe is higher than the temperature of the aerosol passing through the aerosol transport pipe. According to these composite structure manufacturing methods, the adhesion of fine particles and aggregated particles to the nozzle inner wall can be greatly reduced. However, when film formation is performed for a long time, charging due to friction between the powders is unavoidable, and eventually aggregated particles are formed. In addition, the load on the apparatus becomes large, for example, it is necessary to cope with high temperatures for nozzles and pipes.

In Patent Document 4, brittle material fine particles having internal strain are sprayed on the substrate surface at high speed in advance, and the brittle material particles are deformed or crushed by collision with the substrate, and crystallites are bonded to each other through the active new surface that appears. A method of manufacturing an electrostatic chuck that is strongly recombined is disclosed. However, according to this manufacturing method, the strain of the raw material fine particles may affect the film characteristics. In addition, when the film is formed for a long time, the fine particles of the raw material are aggregated, and there is a possibility that the effect due to the distortion cannot be obtained.
Japanese Patent Laying-Open No. 2003-119574 (first page) JP 2003-183847 A (page 1-2) JP 2003-2111030 A (page 1-2)) JP 2002-190512 A (first page)

As described above, in the structure forming process using the AD method, it is difficult to suppress the aggregation of the raw material powder. Therefore, it is not easy to apply the AD film to an application at present. For example, if the film thickness of the piezoelectric film used in the piezoelectric actuator becomes non-uniform, the strength of the applied electric field changes from element to element, resulting in variations in characteristics. Accordingly, there are problems such as poor yield and high cost in the final product using the AD film.
In view of the above points, an object of the present invention is to provide a raw material powder that hardly aggregates even in a film formation process of an AD method for a long time, and a film forming method using such a raw material powder.

  In order to solve the above-mentioned problems, a raw material powder for film formation according to the present invention is a raw material powder used in a film forming method for depositing a composition material of the raw material powder on a substrate by spraying the raw material powder toward the substrate The first particles serving as a base material and the second particles having a particle size smaller than the first particles and fixed so as to cover the surface of the first particles. .

  In addition, the film forming method according to the present invention has a first particle as a base material, a particle size smaller than the first particle, and is fixed so as to cover the surface of the first particle. Step (a) of preparing a film forming raw material powder containing two particles, and spraying the film forming raw material powder prepared in step (a) toward the substrate, thereby forming the film forming material powder on the substrate. And (b) depositing a composition material of raw material powder.

  According to the present invention, it is possible to reduce the radius of curvature and the contact area at the contact portion with adjacent particles by fixing the fine powder having a small particle size to the surface of the base material particle having a large particle size. In such particles whose surface is modified, van der Waals force acting between adjacent particles, liquid cross-linking force, and electrostatic force generated by friction are reduced, so that aggregation of raw material powder can be suppressed. . Therefore, it is possible to stably supply an aerosol having a uniform concentration over a long period of time, and thereby, it is possible to manufacture a high-quality structure having a uniform film thickness without reducing the deposition rate. At the same time, such a structure can be easily increased in area or thickness. Further, by stabilizing the aerosol concentration, the film thickness can be controlled on the order of microns, so that the degree of freedom in designing the structure can be improved.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. The same constituent elements are denoted by the same reference numerals, and the description thereof is omitted.
FIG. 1 is a schematic diagram showing a configuration of a film forming apparatus using an aerosol deposition method (hereinafter referred to as an AD method). This film forming apparatus includes a gas cylinder 1, transfer pipes 2 a and 2 b, an aerosol generation chamber 3, a film forming chamber 4, an exhaust pump 5, a nozzle 6, and a substrate holder 7.

The gas cylinder 1 is filled with nitrogen (N ₂ ), oxygen (O ₂ ), helium (He), argon (Ar), dry air or the like used as a carrier gas. The gas cylinder 1 is provided with a pressure adjusting unit 1a for adjusting the supply amount of the carrier gas. The aerosol generation chamber 3 is a container in which raw material powder (raw material powder) that is a film forming material is disposed. By introducing a carrier gas from the gas cylinder 1 into the aerosol generation chamber 3 through the transport pipe 2a, the raw material powder disposed there is blown up and the aerosol 8 is generated. The generated aerosol 8 is supplied to the nozzle 6 through the transport pipe 2b.

  The inside of the film forming chamber 4 is evacuated by an exhaust pump 5 and thereby maintained at a predetermined degree of vacuum. In the film forming chamber 4, a nozzle 6 for injecting an aerosol 8 and a substrate holder 7 for holding a substrate 9 on which a structure is formed are arranged. The substrate holder 7 is provided with a substrate holder driving section 7a for moving the substrate holder 7 in a three-dimensional manner, whereby the relative position and relative speed between the nozzle 6 and the substrate 9 are controlled.

FIG. 2 is a schematic diagram showing the structure of the raw material powder for film formation according to the first embodiment of the present invention. FIG. 2A shows the surface of the film forming raw material powder, and FIG. 2B shows a cross section of the film forming raw material powder.
As shown in FIGS. 2A and 2B, the film forming raw material powder 10 has a structure in which fine powder particles 12 are fixed so as to cover the entire surface of the base material particles 11. . The base material particles 11 are inorganic insulator particles having an average particle diameter of about 0.1 μm to about 10 μm. The fine powder particles 12 are inorganic insulator particles having an average particle diameter of about 0.01 μm to about 1 μm. The ratio of the average particle diameters of these two kinds of particles is desirably in the range of base material particles: fine powder particles = 10: 1 to 100: 1.

  As shown in FIG. 3 (a), the raw material powder 10 having such a surface structure is in contact with adjacent particles as compared with the raw material powder of only the base material particles 11 shown in FIG. 3 (b). The radius of curvature and the contact area at the part are reduced. Therefore, both van der Waals force and liquid bridge force acting between adjacent particles and electrostatic force generated by friction are reduced. Therefore, aggregation of the raw material powder caused by those forces can be suppressed.

Next, a method for producing the film forming raw material powder shown in FIG. 2 will be described.
First, the powder to be the base material particles 11 and the powder to be the fine powder particles 12 are prepared so as to have a predetermined weight ratio. The weight ratio between the base material particles 11 and the fine powder particles 12 is adjusted according to the particle size of each particle and the coating amount of the fine powder particles. In this embodiment, PZT (Pb (lead) zirconate titanate) powder having an average particle size of approximately 0.3 μm, which is a product of Sakai Chemical Industry Co., Ltd., is used as the base material particle 11. As the powder particles 12, PZT powder having a diameter of about 10 nm produced by a vapor phase method is used, and those materials are prepared so that the weight ratio is base material particles: fine powder particles = 10: 1.

  Next, these two types of particles are put together with ceramic balls having a predetermined weight and diameter, such as zirconia balls, into a pod (mill pod) having a predetermined diameter in a dry state. Then, the two kinds of particles are mixed for a predetermined time by causing the pod to rotate at a predetermined rotation speed using a ball mill device. In that case, in order to prevent the temperature of the powder from rising and the particle size from increasing, it is desirable to rotate the pot while cooling with water. Thereby, a strong compressive force is applied to the base material particles 11 and the fine powder particles 12, the fine powder particles 12 are embedded in the surfaces of the base material particles 11, and the surface of the base material particles 11 is modified. Alternatively, a powder processing apparatus using a mechanical particle composite method (mechanochemical bonding) may be used instead of the ball mill apparatus. For example, Mechanofusion (registered trademark) AMS-Mini-GMP manufactured by Hosokawa Micron Co., Ltd. is a device that combines solid particles in a dry manner by applying mechanical energy to the particles to cause a mechanochemical reaction. It is. Further, a hybridization system (NHS-0 type to NHS5 type) manufactured by Nara Machinery Co., Ltd. may be used. This device is a hybridizer in which fine powder particles are coated on base material particles, and the particles are repeatedly processed by a high-speed rotating rotor with a fixed blade and a circulation pipe, and mechanical thermal energy mainly consisting of impact force is applied to them. This is a device for immobilizing particles by giving to the particles. In any case, it is necessary to prevent impurities from being mixed at a high level.

  The angle of repose of the film-forming raw material powder thus produced (when the powder was dropped on the horizontal plane, the angle formed between the generatrix of the cone-shaped deposit and the horizontal plane) was measured. It was 25 degrees or less with respect to about 45 degrees in the case of normal PZT particles consisting of only base material particles. That is, it can be said that the fluidity of the particles is improved as a result of the surface modification.

FIG. 4 shows the relationship between the elapsed time and the film formation rate when film formation is performed using the film forming raw material powder according to the present embodiment in the film formation apparatus shown in FIG. In addition, in FIG. 4, the film-forming speed | rate at the time of forming into a film using PZT particle | grains (normal powder) of only a base material particle | grain is represented as a comparison.
As shown in FIG. 4, when the film forming raw material powder (surface modified powder) according to the present embodiment was used, a stable film forming speed could be obtained for a long time. Accordingly, the film thickness can be increased without requiring much time, and the film thickness can be controlled by time. Moreover, in the film obtained as a result, the variation in film thickness was reduced. On the other hand, when the normal powder was used, the film formation rate began to greatly decrease soon after the start of film formation, and continued to decrease thereafter. From these results, it can be seen that the film formation speed, film formation efficiency and film quality in the AD method can be improved by modifying the surface of the base material particles.

In the first embodiment of the present invention described above, PZT, which is a kind of piezoelectric material, is used as the film forming raw material powder. In addition to this, an inorganic insulator containing a brittle material in general can be used. it can. For example, lead piezoelectric materials other than PZT, lead-free piezoelectric materials such as KNbO ₃ , dielectric materials such as BaTiO ₃ , insulating materials such as Al ₂ O ₃ , AlN and ZrO ₂ , and optical materials such as PLZT By using the surface-modified raw material powder as in the embodiment, an AD film having good characteristics can be formed.

Next, the film forming raw material powder according to the second embodiment of the present invention will be described.
The film forming raw material powder according to the present embodiment uses PZT as the base material particle 11 shown in FIG. 2 and silica (SiO ₂ ) as the fine powder particle 12. Here, silica is a material used as a sintering aid for PZT. In addition, 4PbO / B ₂ O ₃ , B ₂ O ₃ / Bi ₂ O ₃ / CdO, PbO / PbF ₂ , Ba (Cu _1/2 W _1/2 ) O ₃ + BiFeO ₃ , Pb are used as sintering aids. ₅ Ge ₃ O ₁₁ , LiBiO ₂ or the like can be used. The average particle diameters (diameters) of the base material particles 11 and the fine powder particles 12, the ratio thereof, and the method for producing the raw material powder for film formation are the same as those described in the first embodiment.

Using the film forming raw material powder according to the present embodiment and normal PZT particles not subjected to surface modification, a PZT film was produced under the following conditions.
Deposition temperature: 400 ° C, annealing temperature: 600 ° C
Polling conditions: 3 kV at 100 ° C
As a result, in the PZT film using normal PZT particles, the piezoelectric constant was d31 = 50, whereas in the PZT film using the film forming raw material powder according to the present embodiment, the piezoelectric constant d31 = 100 was obtained. Thus, sintering can be accelerated | stimulated by forming AD film using the raw material powder which fixed the sintering adjuvant to the surface of base material particle | grains. Therefore, even when the film formation temperature is lowered, the function of the film can be improved.

In the present embodiment, the raw material powder is produced using PZT as a base material and silica as a sintering aid, but various other combinations of materials can be used. For example, when forming an alumina (Al ₂ O ₃ ) film, magnesium oxide (MgO) or silica is used as a sintering aid, and when forming a silicon nitride (Si ₃ N ₄ ) film, alumina or A sintering aid may be selected according to the base material, such as using yttrium oxide.

  As described above, according to the present invention, a high-quality AD film having a uniform film thickness can be formed by performing the AD method using the surface-modified film forming raw material powder. Therefore, when such an AD film is applied to a piezoelectric film for an actuator, the electric field strength applied to each element can be made uniform, thereby stabilizing the quality of the final product and improving the product yield. Can be made. In addition, when such an AD film is applied to an ultrasonic transducer used in an ultrasonic diagnostic apparatus, the operation accuracy of each ultrasonic transducer can be increased, so that an ultrasonic image with good image quality can be obtained. it can. Furthermore, by using surface-modified film forming raw material powder, a high-quality, large-area film can be formed. By producing a wide range of inkjet heads, an inkjet capable of outputting large images with high image quality A printer can be manufactured.

  The film forming raw material powder according to the present invention can be produced using various methods in addition to the method described in the first embodiment. For example, JP-A-5-317579 discloses a method for producing composite particles used as a raw material for powder metallurgy by coating ceramic particles on the surface of metal particles. JP 2003-277295 A and JP 2003-275281 A can improve the fluidity and productivity of a drug powder by modifying the surface of the drug powder using a lubricant. A method for producing drug-containing composite particles is disclosed. By using these composite particle manufacturing methods, it is possible to produce a raw material powder suitable for film formation by the AD method.

  The present invention is applicable to an aerosol deposition (AD) method in which a raw material composition material is deposited on a substrate by spraying the raw material toward the substrate.

It is a schematic diagram which shows the film-forming apparatus by AD method. It is a schematic diagram which shows the structure of the raw material powder for film formation which concerns on the 1st Embodiment of this invention. It is sectional drawing which compares and shows the raw material powder for film formation which concerns on the 1st Embodiment of this invention, and the raw material powder only of a normal base material particle | grain. It is a figure showing the relationship between the elapsed time at the time of performing the film-forming by AD method, and the film-forming speed | rate. It is a schematic diagram which shows a mode that an aerosol is produced | generated.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas cylinder 1a Pressure adjustment part 2a, 2b Conveying pipe 3, 101 Aerosol production | generation chamber 4 Film formation chamber 5 Exhaust pump 6 Nozzle 7 Substrate holder 7a Substrate holder drive part 8 Aerosol 9 Substrate 10 Raw material powder 11 Base material particle 12 Fine Powder particle 100 Raw material powder 102 Winding nozzle 103 Pressure adjusting nozzle 104 Aerosol outlet tube 105 Shaking table

Claims (14)

A raw material powder used in a film forming method for depositing a composition material of the raw material powder on the substrate by spraying the raw material powder toward the substrate,
First particles as a base material;
A second particle having a particle size smaller than the first particle and fixed to cover the surface of the first particle;
A raw material powder for film formation comprising: The average particle diameter of the first particles is 0.1 μm to 10 μm,
The average particle diameter of the second particles is 0.01 μm to 1 μm.
The raw material powder for film formation according to claim 1.   3. The film forming raw material powder according to claim 1, wherein a ratio of an average particle diameter of the first particles to an average particle diameter of the second particles is 10: 1 to 100: 1.   The film forming raw material powder according to claim 1, wherein the first particles include an inorganic insulator.   The film forming raw material powder according to claim 4, wherein the first particles include PZT (Pb (lead) zirconate titanate).   The raw material powder for film formation according to any one of claims 1 to 5, wherein the second particles have the same composition as the first particles.   The film forming raw material powder according to any one of claims 1 to 5, wherein the second particles are a sintering aid for a material forming the first particles. The film forming raw material powder according to claim 7, wherein the second particles are formed of silica (SiO ₂ ). A film forming raw material including first particles as a base material and second particles having a particle diameter smaller than that of the first particles and fixed so as to cover the surface of the first particles A step of preparing powder (a);
(B) depositing the composition material of the film forming raw material powder on the substrate by spraying the film forming raw material powder prepared in the step (a) toward the substrate;
A film forming method comprising: A step (a ′) of generating an aerosol by blowing up the film forming raw material powder prepared in the step (a) with a gas;
Step (b) comprises injecting the generated aerosol toward a substrate;
The film forming method according to claim 9. The average particle diameter of the first particles is 0.1 μm to 10 μm,
The average particle diameter of the second particles is 0.01 μm to 1 μm.
The film-forming method of Claim 9 or 10.   The film forming method according to claim 9, wherein a ratio of an average particle diameter of the first particles to an average particle diameter of the second particles is 10: 1 to 100: 1.   The film forming method according to claim 9, wherein the second particles have the same composition as the first particles.   The film-forming method of any one of Claims 9-12 whose said 2nd particle | grain is a sintering auxiliary agent of the material which forms said 1st particle | grain.

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