JPH02225677A - Film formation - Google Patents

Abstract

PURPOSE:To obtain a film in which respective contents of powder and pore are changed continuously or by stages at high speed into a large area by introducing a powder into a reaction vessel to deposit the powder onto the surface of a base material and simultaneously forming a film on the above surface by means of chemical vapor growth. CONSTITUTION:In the course of film formation by a chemical vapor growth method, a powder having a composition or crystalline structure (including amorphous one) similar or dissimilar to that of a film is introduced. The above powder is deposited on the surface of a base material, and simultaneously, the film is formed on the above surface by means of chemical vapor growth. The composition, porosity, and structure of the film can be easily controlled by controlling the composition, crystalline structure, magnetic properties, grain size, shape, and quantity of the powder to be supplied or the composition, quantity, etc., of gaseous raw material. By this method, the uniform film having gradient function or network structure can be obtained at high speed. This film can be used for insulator electric conductor, heat insulator, catalyst support, heat sink, etc.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to the production of substrates made of dense or porous inorganic materials or growth materials by simultaneously producing chemical vapor deposition (CVD) and powder deposition. Forming a single-phase or multi-phase coating on the surface, or forming a thin or thick film in which the composition or pore content changes uniformly, continuously, or stepwise, or in which powder is distributed in a network in the film. This is a film forming method that can be used.

[Prior art] As a conventional method for forming films of metals, ceramics, etc., for example, "Applied Physics Vol. 54" (1980) P6B7-8
93, there is a gas deposition method for ultrafine particles. This method uses ultrafine particles (less than 0.1 μm) of metal or ceramics produced by evaporation in gas, etc.
This is a method of forming a film by blowing it onto the target object using an air current. In addition, as another method, Ceramics Association Journal No. 95 @ (Showa 6
2 years) P70-75 or JP-A-81-1581177
The PPCVD method (Particle
e Pre-efpHatlon Aided C
Chemical Vapor Depositio
n: ultrafine particle thermophoresis CVD). This method involves generating ultrafine particles through a gas phase reaction in a reaction tank, depositing the ultrafine particles onto a substrate using thermophoresis, and allowing a particle growth reaction to proceed on the surface of the ultrafine particles deposited on the substrate. This is a method of forming a film by filling in the spaces between ultrafine particles.

[The invention seeks to solve a! Problem] It is difficult to control the pores in porous films obtained by the conventional gas deposition method described above, and in this method, it is necessary to move the base material relative to the nozzle during film formation, which reduces the film area. Expansion is severely restricted.

In the PPCVD method, thermal control of phenomena such as the generation of powder in a gas, the gas phase reaction with the surface reaction on the substrate, and the thermophoresis of the powder is performed at the same time. It is difficult to achieve optimal conditions, and there is a limit to increasing the film formation rate. Furthermore, it is difficult to obtain a multiphase film with an arbitrary composition, it is difficult to arbitrarily control the #fl texture and pores, and it is basically impossible to increase the speed for systems with slow gas phase reactions. It was possible.

The present invention achieves both ease of control of composition, structure, and pore content, which was impossible with these conventional film forming methods, and
It is an object of the present invention to provide a film forming method that can rapidly and over a large area produce a film in which the composition, structure, and pore content change continuously or stepwise, or in which powder is uniform or distributed in a network shape in the film. This is the purpose.

[Means for Solving the Problems] The present invention provides a method for forming a film by chemical vapor deposition using a powder having a composition or crystal structure (including amorphous) that is different from or similar to that of a film formed by chemical vapor deposition. When a ferromagnetic material is used as the powder, the content of the powder or pores is constant, continuous, or stepwise changed. This film forming method is characterized in that the powder is capable of forming a network in the film.

Figures 1 to 6 are diagrams schematically showing the structure of membranes produced by the method of the present invention, where m is the product produced by chemical vapor deposition, p is the powder deposited by thermophoresis, and S are stomata.

In other words, in conventional film-forming methods that utilize gas-phase reactions, gas or atomized liquid is supplied as the raw material for the film, whereas in film-forming methods that rely on powder deposition, only powder is supplied as the raw material for the film. However, in the present invention, powder and gas (or powder and atomized liquid) are simultaneously supplied as raw materials for the membrane, and the powder is deposited on the substrate and a gas phase reaction is caused. , which is different from conventional film formation methods.

In the present invention, a powder serving as a film forming raw material such as TiC as shown in the examples is placed in an aerosol state in a reaction tank using a gas that is not a film forming raw material such as N2 or a film forming raw material gas such as NH3 as a carrier gas. to be introduced. One type of powder may be used, but two or more types with different compositions, crystal structures, magnetic properties, shapes, particle sizes, etc. can be used, and
The introduction into the reaction tank may be performed through a plurality of piping.

Methods for mixing the carrier gas and powder include a method of mixing pre-generated powder using a mixer, a plasma jet method, a /% live plasma method, and an evaporation method in gas using arc discharge heating. By evaporation method in gas etc.
There is a method of simultaneously generating powder and mixing it with a carrier gas.

According to the above-mentioned evaporation method in gas, etc., the production rate of powder is fast;
Active powder is suspended in the gas at the time of generation, and the pressure at the time of generation is within the pressure range suitable for conveying the powder.The gas at the time of generation can be used as a conveyance gas, and there is no surface contamination of the powder.
It's convenient.

In the present invention, the powder is deposited on the substrate by thermophoresis. To do this, the temperature of the base material is lower than that of the gas phase, and a temperature gradient of 10 Kcm or more is created between the two. Due to the existence of the temperature gradient, the powder suspended in the gas is caused by thermophoresis. It migrates towards the substrate and is deposited on the substrate.

In the present invention, it is desirable that the substrate be in contact with or close to the flow path of the gas (or atomized liquid) and powder introduced into the reaction tank.

In addition, regarding the angle between the gas flux transporting the powder and the base material, if the temperature and temperature gradient of the base material are constant, the amount of powder deposited on the base material will be constant. So,
It may be set arbitrarily. Furthermore, the movement speed of the powder due to thermophoresis is sufficiently higher than the gravitational sedimentation speed, for example,
When the particle size of the powder is 4 μm or less, the substrate may be placed horizontally, vertically, or inclined in the reaction tank.

Next, an apparatus suitable for carrying out the present invention will be explained.

FIG. 7 is an example. In the figure, reference numerals 1 and 2 are inlets for the powder carrier gas, the flow rate of which is controlled by a needle valve 5 and a stop valve 8. The carrier gas is mixed with powder by the powder supply device 22 and controlled to a desired temperature, and is supplied into the reaction tank 21 through the nozzle 13 via the needle valve IO. The raw material gas or atomized raw material liquid for film formation by gas phase reaction is supplied into the reaction chamber 121 from the gas inlets 3 and 4 via the needle valve 6, stop valve 9 and nozzle 14.15. ing. The base material 18 is a heater 19
The surface of the reaction tank 21 facing the base material 18 is heated by the heater 20, and these heaters 1
9.20 are individually controlled to add a temperature gradient. The reaction tank 21 has a pressure gauge 17. The gas in the reaction tank 21 is discharged from the gas outlet 16 through the stop valve 1.
2 and the needle valve 7 or stop valve 11, and after passing through the cold trap 23, the vacuum pump 24
is discharged.

FIG. 8 shows another implementation device, which differs from the one in FIG. 7 in the method of controlling the temperature of the base material. The reaction tank 28 is heated by the heater 27, and the base material 25 is cooled by the refrigerant passing through the refrigerant introduction pipe 2B, so that a temperature gradient exists. Further, the base material 25 is held in a reaction tank 28 by a coolant introduction pipe 26. Note that 29 in the figure is a gas exhaust port.

[Function] In the present invention, when controlling the film forming state and film properties such as the film forming rate, the factors include the surface reaction rate of the raw material gas, the thermophoretic velocity of the powder in the gas, and the powder to be supplied. There are different types of powder represented by the composition, crystal structure, magnetic properties, shape, particle size, etc., and the amount of powder to be supplied to the reaction tank. The surface reaction rate changes depending on the substrate temperature, pressure, raw material gas supply amount, raw material gas composition, etc. Thermophoretic velocity changes primarily due to temperature gradients.

The relative density of the membrane as shown in FIGS. 1, 2 and 3,
Control of pores, such as pore size and pore content, and control of membrane structure can be achieved by selecting the surface reaction rate, thermophoresis rate, the amount of powder supplied, and the shape and particle size of the powder to be supplied. .

The structure of the film can also be selected by selecting the crystal structure and magnetic properties of the powder. When a ferromagnetic material is used as the powder, as shown in Figure 4, the powder forms a network in the film. The composition of the film formed can be controlled by selecting the surface reaction rate, the thermophoresis rate, the amount of powder supplied, and the composition of the supplied powder. By changing the above-mentioned control continuously or stepwise, it is possible to produce a film which is a functionally graded material with a wide range of features as shown in FIGS. 5 and 6. Furthermore, the film formation rate can be controlled by the surface reaction rate, thermophoresis rate, or the amount of powder supplied. Since the film is a mixture of products from the surface reaction and powder from the deposition, the growth of columnar crystals and the like due to the surface reaction can be controlled by the powder. Furthermore, it is possible to increase the area of the film to the extent that it is possible to do so using a general CVD method. Furthermore, the film formation rate is lower than that of conventional CV due to powder deposition by thermophoresis.
It is faster than the D method.

[Example] Implementation P41 As the powder supply bag rl122 in FIG. 7, powder was supplied and the powder was mixed with a carrier gas by an in-gas evaporation method using arc discharge heating. That is, by melting and vaporizing Ti by arc discharge and introducing N2 gas through gas inlet 1, ultrafine TEN particles having a particle size of 50 to 100 ns were synthesized.

Next, the TIN ultrafine particles are introduced into the reaction tank 21 using N2 gas. On the other hand, TiCl4, N
A mixture of H3 and N2 gases was introduced into the reaction tank 21, and the inside of the reaction tank was maintained at 750 to 1000°C and 20 to 20 QTorr.

The temperature of reaction tank 2■ is controlled by heater 20.19.
A temperature gradient is created between the gas and the substrate so that Tg>Ts (CTg: gas temperature, Ts: substrate temperature), and TAN ultrafine particles are deposited on the Al2O3 substrate by thermophoresis, and then the TIN ultrafine particles are deposited on the deposited TIN ultrafine particles. A TiN film was deposited by the reaction of TiCl4, NH3, and N2.

As a comparative product, one without the process of introducing ultrafine particles (C
VD reaction only), without reaction gas introduction process (
(only ultrafine particle deposition) and one with no difference in gas temperature and substrate temperature were also created. The film formation rate of the obtained sample was measured.

The results are shown in Table 1.

Table 1 Example 2 In the powder supply method shown in FIG.
The mixed gas is mixed with the N2 gas introduced into the reactor tank 28 shown in FIG. 8. On the other hand, gas inlet 3 to 5
iC14, N2 gas and NH3 gas are respectively introduced into the reaction tank 28 from the gas inlet 4, and the inside of the reaction tank 28 is heated to 1500-1800°C and 30-200 Torr by the heater 27.
It was held at r. The A120z board 25 is cooled by flowing a predetermined amount of air through the refrigerant introduction pipe 26, and Tg>Ts(
A temperature gradient is provided between the gas and the substrate so that Tg: gas temperature, Ts: substrate temperature), and TiC ultrafine particles are deposited on the A, 1203 substrate by thermophoresis, and the TiC ultrafine particles are deposited on the deposited Ti-C ultrafine particles. Then, by the reaction of 5ie14, NH3, and N2, S
An i3N+ film was deposited. As a result, a dense film in which TiCHi fine particles were dispersed in 5i3Na was obtained. Regarding the produced film, the film formation rate and the produced phase were identified by X-ray diffraction. The results are shown in Table 2.

Table 2 Example 3 In FIG. 7, the powder supply method was as follows: SIC ultrafine particles (α-5iC) placed in the powder supply device in advance
It is mixed with H2 gas introduced through the gas inlet 1 and introduced into the reaction tank 28 shown in FIG. 7. On the other hand, CH35iC1:+ gas is introduced into the reaction tank 28 from the gas inlet 3, and the inside of the reaction tank is heated at 1200 to 1800 by the heater 27.
The temperature was maintained at 80 Torr.

The Al2O3 substrate 25 is cooled by flowing a predetermined amount of air through the coolant introduction pipe 2B, and a temperature gradient is created between the gas and the substrate so that Tg>Tta (Tg: gas temperature, TS: substrate temperature). The SiC ultrafine particles introduced from the powder supply device are deposited by thermophoresis, and the deposited S
SjC was precipitated by thermal decomposition reaction of CH38tCI3 on iC ultrafine particles.

Regarding the produced film, the film formation rate, relative density measurement, and Xv
The generated phase was identified by a-diffraction.

Table 3 shows the results.

Table 3 By controlling the temperature of the substrate and the gas and the temperature gradient between the substrate and the gas as shown in Table 3, it is possible to obtain s I CHI from porous to dense in any relative density and in a short time. Can be done.

Example 4 As the powder supply device 22 in FIG. 7, powder was supplied and mixed with a carrier gas by an in-gas evaporation method using arc discharge heating. As the metal to be melted and evaporated, COI, which is a ferromagnetic material, or Mo, which is a paramagnetic material, was used. That is, by melting and vaporizing Co1 or Mo by arc discharge and introducing gas A from the gas inlet, CO or Mo ultrafine particles having an average particle size of 4Qn* were synthesized.

Next, the generated COI or Mo ultrafine particles are introduced into the reaction tank 28 in FIG.
Tt (C3HrO) 4% A by gas inlet 3
R gas was introduced into the reaction tank 28, and the inside of the reaction tank 2B was maintained at 500° C. and 100 Torr by the heater 27. A
The l2O3 substrate 25 is cooled by flowing a predetermined amount of air through the refrigerant introduction pipe 26, and a temperature gradient is created between the gas and the base material so that Tg>Ts (Tg: gas temperature, TS: base material temperature). COI or Mo ultrafine particles are deposited on the substrate by thermophoresis, and Ti is deposited on the deposited ultrafine particles.
An rtoz film was precipitated by thermal decomposition of (C3HrO)4. This produced a dense TiO2 film in which ultrafine CO particles were dispersed in a network, or a dense TiO2 film in which ultrafine Mo particles were uniformly dispersed. Fabrication The sheet resistance value, film thickness, and content of ultrafine metal particles were measured using EDX for the resulting film.The results are shown in Table 4.

Table 4 It can be seen that because the CO ultrafine particles are distributed in TiO2 in a network, it has higher electrical conductivity than in the case of Mo.

Example 5 In the powder supply method shown in FIG.
The mixture is mixed with the N2 gas introduced into the reactor tank 2B in FIG. 8. On the other hand, S from gas inlet port 3
IC+4 and N2 gas, NH gas and gas are respectively introduced into the reaction tank 28 from the gas inlet 4, and the inside of the reaction tank 28 is heated at 150G -1800℃, 30-200T by the heater 27.
It was held at orr. Si:+N* The substrate 25 is cooled by flowing a predetermined amount of air through the refrigerant introduction pipe 2B, and Tg>
Ti
The deposited TiC particles are deposited by thermophoresis.
A Si3N4 film was deposited on the ultrafine particles by a reaction of 5iC1+, NH3, and N2. By controlling the supply amount of TiC ultrafine particles and the temperature gradient between the gas temperature in the reaction tank 2B and the Si3N4 substrate, a film that is a functionally graded material in which the composition of TiC and 5t3N4 changes continuously can be rapidly formed. did it. Regarding the produced film, the produced phase was identified by X-ray diffraction and the EPMA composition analysis of the film cross section was performed. The results are shown in Table 5, and the EPMA composition analysis results are shown in Figures 9 and 10.
As shown in the figure.

Table 5 [Effects of the invention] In the present invention, unlike conventional film forming methods, by controlling the composition, crystal structure, magnetic properties, particle size, shape, amount, or source gas composition and amount of the supplied powder, By easily controlling the composition, porosity, or structure of the film, it is possible to rapidly obtain a film that is uniform, has a functionally graded function, or has a network structure. The film produced according to the present invention can be effectively used as an insulator, a conductor, a heat insulator, a catalyst carrier, a heat sink, an intermediate material for joining different materials, and the like.

[Brief explanation of the drawing]

Figures 1 to 6 are schematic diagrams of membrane structures produced by the method of the present invention, Figure 7 is an explanatory diagram of a reaction apparatus suitable for implementing the present invention, and Figure 8 is another example suitable for implementing the present invention. 9 and 10 are graphs showing the results of EPMA composition analysis of Examples.厘... product formed by chemical vapor deposition, p... powder deposited by thermophoresis, S... pores, 1.
2.3.4...Gas inlet, 5.8.7.10...Needle valve, 8.9,11
．． 12... Stop valve, 13... Nozzle for supplying gas and powder, 14.15... Nozzle for supplying membrane raw material gas, 16... Gas discharge port, 17... Pressure gauge, 18 ...Base material, 19... Heater for adjusting base material temperature 20... Heater for heating the opposing surface of the base material, 21... Reaction tank, 22... Powder supply device, 23... Cold Trap, 24... Vacuum pump, 25... Base material, 2B
... Refrigerant introduction pipe, 27 ... Heater for heating the opposing surface of the base material 28 ... Reaction tank, 29 ... Gas discharge port. E 1 Figure 2 Figure 2 Figure 2 Figure 2

Claims (9)

[Claims] (1) During film formation by chemical vapor deposition, one or more types of powder are introduced into the reaction tank to deposit the powder on the surface of the substrate and simultaneously form a film by chemical vapor deposition. A film forming method characterized by: (2) The film forming method according to claim 1, wherein the powder introduced into the reaction tank has a composition or crystal structure (including amorphous) that is different from or the same as that of the film formed by chemical vapor deposition. (3) The film forming method according to claim (1), wherein the powder introduced into the reaction tank is a ferromagnetic material, and the powder is caused to form a network in the film. (4) The film forming method according to claim (1), wherein in forming the film on the surface of the substrate, pores are formed in the film. (5) Claims (1), (2), (3) or (4) in which the powder or pores are uniformly dispersed or contain powder or pores whose content changes continuously or stepwise.
) Described film formation method. (6) The film forming method according to any one of claims (1) to (5), further comprising introducing aerosolized powder into the reaction tank. (7) The film forming method according to any one of claims (1) to (5), wherein the powder is produced by a gas phase reaction in a reaction tank. (8) The film forming method according to any one of claims (1) to (5), wherein the powder is deposited on the surface of the substrate by thermophoresis. (9) The temperature gradient formed between the gas phase and the substrate surface is 10Kc
8. The film forming method according to claim 8, wherein the temperature of the gas phase is higher than m^-^1 and the temperature of the gas phase is higher than the surface of the substrate.