JP4859656B2 - Film forming method and film forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film deposition method capable of easily depositing a uniform film without changing the composition of powder. <P>SOLUTION: Regarding the method in this invention, high pressure d.c. voltage is applied to a space between an upper electrode 5 holding a substrate K in which a thin film is formed on the surface and a lower electrode 7 mounted with powder P as a film material in a vessel 3 under a vacuum, so as to form an electrostatic field between both the electrodes 5, 7, and the powder P is reciprocated between both the electrodes 5, 7 by an electric field generated at the electrostatic field, thus the powder P is stuck to the surface of the substrate K, so as to deposit a film. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a film forming method and a film forming apparatus for forming, on a substrate surface, a thin film that exhibits functionality, for example, when a functional device is manufactured.

As a film forming method for forming a thin film exhibiting functionality on the surface of a substrate, a method using an electrostatic field, for example, a method using electrostatic coating, a method using sputtering, or the like is known.
In the electrostatic coating method, powder carried by air is charged when passing through the corona discharge electrode provided at the tip of the nozzle, and the powder is attached to the workpiece by the charged electric charge and spraying force. (For example, refer to Patent Document 1).

In addition, a sputtering method is a method in which a film forming material (also referred to as a target) is ionized by applying high energy, and the ionized film forming material is attached to a workpiece (for example, see Patent Document 2).
JP 2000-176325 A JP2006-2220

  However, according to the electrostatic coating method, the amount of electrification is small because the powder moves quickly at the nozzle portion that gives electric charge, and therefore the adhesion is very weak. There is a problem that it is difficult to form a film with a powder that easily escapes electric charges, because a process such as bonding is required.

  Moreover, in the method by sputtering, since high energy is given to the powder and ionization is performed, the composition of the powder is changed (the stoichiometric composition is broken). That is, when a powder that exhibits a specific function such as an electronic device is formed by this method, there is a problem that the performance that should be originally obtained cannot be exhibited due to the composition change. Furthermore, the film formation rate is very slow, and in order to ensure the uniformity of the film, it is necessary to control the plasma density, and there is a problem that film formation over a large area is difficult.

  Accordingly, an object of the present invention is to provide a film forming method and a film forming apparatus capable of easily forming a uniform film without changing the composition of the powder.

In order to solve the above-mentioned problem, a film forming method according to claim 1 of the present invention includes one electrode for holding a substrate on which a film is formed on the surface and the other electrode on which powder as a film material is placed. A DC voltage is applied between the two electrodes to form an electrostatic field between the two electrodes,
In this method, the powder, which is the film material, is reciprocated between the electrodes by the electric field generated in the electrostatic field, and the powder is adhered to the substrate surface.

A film forming method according to claim 2 is the film forming method according to claim 1, wherein the film forming is performed under vacuum.
According to a third aspect of the present invention, there is provided a film forming method according to the first or second aspect, wherein a substrate having a surface provided with a conductive material is used.

A film forming method according to claim 4 is a method using carbon nanotubes or an adhesive as the conductive material provided on the substrate surface in the film forming method according to claim 3.
A film forming method according to claim 5 is a method of mixing carbon nanotubes with a film material in the film forming method according to claim 1.

  Further, the film forming method according to claim 6 is the film forming method according to any one of claims 1 to 5, wherein plasma is generated in a space region between both electrodes and ions are applied to the powder surface to activate the film. It is a method to make it.

A film forming apparatus according to claim 7 is a film forming apparatus for forming a film by attaching a powder to the surface of a substrate,
A DC voltage is applied between the upper electrode disposed in the upper part of the container and capable of holding the substrate, the lower electrode disposed under the upper electrode in the container and capable of mounting powder, and the two electrodes. DC power supply,
And when performing film formation,
A DC voltage is applied between the two electrodes to form an electrostatic field, and a Coulomb force is applied to the powder placed on the lower electrode by the electric field generated in the electrostatic field to cause the powder to flow between the two electrodes. The powder is attached to the surface of the substrate by reciprocating.

  According to an eighth aspect of the present invention, there is provided the film forming apparatus according to the seventh aspect, further comprising a plasma generator for generating plasma in a space region between at least both electrodes in the container.

  Furthermore, the film forming apparatus according to claim 9 is the film forming apparatus according to claim 7 or 8, wherein the particle size for controlling the size of the powder moving from the lower electrode to the substrate side between both electrodes. A control board is arranged.

  According to the film forming method and the film forming apparatus, a direct current voltage is applied between the lower electrode on which the powder is placed and the upper electrode, and the powder is moved back and forth between the two electrodes, thereby causing the substrate to move. Since the film is formed, unlike the case where sputtering is performed by hitting the target with electrons, the composition does not change, and the powder moves back and forth between the electrodes many times. Since the direction is three-dimensional, a uniform film can be easily formed on the substrate surface.

[Embodiment 1]
Hereinafter, a film forming apparatus and a film forming method according to Embodiment 1 of the present invention will be described with reference to the drawings.

  In the first embodiment, when a functional device (for example, a power generation cell of a solar battery) is manufactured, so-called film formation is performed in which a thin film that can exhibit a predetermined function is formed on a substrate. A film forming method and a film forming apparatus will be described.

First, the film forming apparatus will be described.
As shown in FIG. 1, the film forming apparatus includes a container 3 (also referred to as a vacuum container) to which a vacuum pump 1 is connected via an air discharge pipe 2, and the axial direction of the container 3 is the vertical direction. A cylindrical body (which is a cylindrical body, which can also be referred to as a cylindrical dielectric body) 4 which is vertically arranged and made of an insulating material such as glass, and an upper portion in the cylindrical body 4 An upper electrode 5 that can hold the substrate K to be deposited, and a powder P that is also disposed in the lower part of the cylindrical body 4 and that is a powdery deposition material (also referred to as a film raw material) can be placed. The lower electrode 7 held by the electrode holding member 6, the DC power supply 8 for applying a high-voltage direct current between these electrodes 5, 7, and wound around the outer peripheral surface of the cylindrical body 4 and connected to the high-frequency power supply 9 Plasma is generated in the space region between the electrodes 5 and 7 Frequency coil (cooling water therein flows) and a 10 Metropolitan that.

  An annular edge 6a is provided around the electrode holding member 6 for holding the lower electrode 7 so that the powder P placed on the lower electrode 7 does not fall. , 7 are provided with heaters 11 and 12 (incorporated). Further, an inert gas supply pipe 13 for supplying an inert gas such as nitrogen gas, argon gas, or helium gas is connected to the bottom wall portion of the container 3.

A film forming method for forming a thin film on the substrate K in the above structure will be described.
First, the substrate K having a conductive adhesive (an example of a conductive material, such as a conductive synthetic resin) applied to the surface (the surface facing the lower electrode) is held on the lower surface of the upper electrode 5. At the same time, after the powder P, which is a film forming material, is placed on the lower electrode 7 in the annular edge 6a of the electrode holding member 6, the heaters 11 and 12 disposed on the electrodes 5 and 7 are operated.

The heaters 11 and 12 heat the conductive adhesive for the upper electrode 5 to increase the adhesiveness, and the powder P placed on the lower electrode 7 is heated to evaporate water.
Then, after the inside of the container 1 is evacuated to about 1 Pa by the vacuum pump 1, an inert gas such as nitrogen gas, argon gas, helium gas is supplied.

  Next, a high-frequency current is passed through the high-frequency coil 10 by the high-frequency power source 9 and a high-voltage DC voltage is applied between the electrodes 5 and 7 by the DC power source 8. Here, the positive electrode is connected to the upper electrode 5, and the negative electrode is connected to the lower electrode 7.

  Therefore, a negative charge is given to the powder P placed on the lower electrode 7, and a force [so-called Coulomb force] directed toward the upper electrode 5 due to the electric field strength E of the electrostatic field generated between the electrodes 5 and 7. Since (F = qE)] is given, the powder P moves (jumps out) to the upper electrode 5 side at a high speed.

  A part of the powder P moved to the upper electrode 5 side adheres to the conductive adhesive applied to the surface of the substrate K, but the remaining powder P is positively charged by the upper electrode 5 (electrons are absorbed). It is released and has a positive charge), and then moves toward the lower electrode 7 at a high speed, and is again negatively charged (given electrons) and moves to the upper electrode 5.

  As described above, the powder P is reciprocated between the electrodes 5 and 7, and during this reciprocation, the amount of adhesion to the substrate K gradually increases and a thin film having a predetermined thickness is formed. become. By the way, since the movement direction of the powder P discharged from the electrodes 5 and 7 is three-dimensional [so-called cosine law (COS law)] with respect to the entire electrode, However, the powder P adheres evenly to the entire substrate K.

  In addition, since the inert gas is turned into plasma inside the cylindrical body 4 by the high-frequency coil 10, the surface of the powder P is ionized and activated to facilitate movement of the powder. In this activation, a hydrogen group (—H), a hydroxyl group (—OH) or the like is generally adsorbed on the surface of the substance, and therefore, when the substances are stacked, the binding force is hindered. In other words, the group adsorbed on the surface is removed by passing through the plasma (that is, an excessive or insufficient state of electrons occurs on the surface), and the surface is activated.

  In addition, when an inert gas is used, for example, in the atmosphere containing oxygen, hydrogen groups adsorbed on the surface of the powder are removed and activation is temporarily promoted, but oxygen in the plasma reacts. This is to prevent oxidation and further stabilization.

  Moreover, it is preferable to use rare gases, such as argon gas and helium gas, among inert gas. This is because plasma is easily generated and does not oxidize, so that it can be attached to the substrate with its surface activated.

  Furthermore, although the inside of the container 3 is in a vacuum state, plasma can be generated even under atmospheric pressure replaced with an inert gas, but in order to generate plasma with low power, a vacuum in the range of 1 to 1000 Pa is used. It is because it is preferable to make it a state. That is, when a vacuum state is established, the movement of electrons and gas ions in the plasma becomes intense, and the surface can be further activated.

  As described above, since the high voltage DC voltage is applied between the lower electrode on which the powder is placed and the upper electrode, the powder is reciprocated between the two electrodes. A thin film that adheres gradually and uniformly to the surface of the substrate held by the electrode and exhibits a predetermined thickness of functionality is formed. Specifically, the film is formed by first adhering to the conductive adhesive and then colliding between the already adhering powders and decreasing. In other words, unlike the case where sputtering is performed by irradiating the target with electrons, the powder is moved by the electric field generated by the electrostatic field, so that the composition does not change and the powder does not change between the two electrodes. Since the movement direction is three-dimensional, the thickness of the thin film formed on the substrate surface is naturally uniform, in other words, the film thickness can be easily uniformed.

  In addition, high power is not required to attach the powder to the substrate (the current is very small even at high voltage), and the desired function is achieved at low cost without changing the composition of the powder to be laminated. Sex devices can be obtained. In addition, as described below, at least a solvent is not required, so that it is environmentally friendly.

Here, the case where the film-forming method mentioned above is applied to manufacture of the power generation cell of a dye-sensitized solar cell is demonstrated.
The dye-sensitized solar cell currently developed is applied to a glass substrate or a plastic substrate by applying a photocatalyst such as TiO ₂ (having a particle diameter of, for example, about several tens of nm) pasted with an organic solvent, followed by drying / baking. The film formation is performed through the conjugation process. The catalyst is manufactured by impregnating a dye into the catalyst and putting an electrolyte solution between the catalyst and the counter electrode.

By the way, when forming TiO ₂ on a substrate, there is a firing step as a step of fixing a paste or powder to the substrate, but in the case of a powder, that is, a powder, firing at a temperature close to 400 ° C. Has been. When this baking temperature is high, the ITO film of the substrate is oxidized by the temperature, and the film resistance value is increased, resulting in a decrease in battery efficiency.

  As a method for lowering the firing temperature, recently, a paste dispersed in a polymer organic solvent or the like is used. As the organic solvent, a material that is not preferable in terms of environment is used.

Also, adding a dye to the TiO ₂ is (covering the TiO ₂ with a dye) that is dyed with the dye after the formation of TiO ₂ is a method, would include steps such as re-dried.
Furthermore, as for the electrolyte (which is also an electrolytic solution), an iodine-based electrolytic solution has been often used so far from the viewpoint of electrical conductivity. However, in order to improve the liquid leakage from the sealing portion, the development of a battery using a gel or a solid electrolyte is also in progress.

  In the production of a power generation cell using a solid electrolyte, as in the case of a catalyst, a solvent or pasted material is fixed to the counter electrode side by firing, and the cell is produced by bonding the catalyst side substrate and the electrolyte side substrate. ing.

Here, what is important is that the interface and contact area between the electrolyte and the catalyst greatly affect the battery performance.
Because, if the electrolyte is liquid, it can gain an area for the exchange of electrons by entering the gap of the catalyst, but in the case of a solid electrolyte, since the exchange of electrons is performed only on the bonded surface, as a result Conversion efficiency will drop.

Therefore, when producing a power generation cell using the film forming method according to the present invention, first, a TiO ₂ surface is obtained by immersing TiO ₂ powder of 20 to 40 nm in a solvent dissolved with a coumarin-based dye as a dye. A dye is attached to the surface.

Next, CuI (copper iodide) powder (particle diameter of about 20 to 50 nm), which is a solid electrolyte, is mixed with the TiO ₂ powder in a weight ratio of 7: 3 or 8: 2 at the bottom. The electrode 7 is supplied (placed), and the upper electrode 5 holds the glass substrate K with the ITO film, and the distance from the lower electrode 7 to the substrate K is 20 mm. A DC voltage of 20 kV) was applied. After about 20 seconds from the application of the DC voltage, a thin film having a thickness of about 10 μm was obtained.

  Next, CuI powder having the same particle size as described above was deposited on the thin film with a thickness of about 10 to 20 μm by the same operation as described above. At this time, the powder was adhered while performing plasma activation treatment.

While pressing a glass substrate or a metal plate such as SUS on which the Pt film was formed on the power generation cell thus obtained, the periphery was hardened with an epoxy resin so as not to leave the substrate, and a solar cell was manufactured.
As a result of measuring the performance of this battery with simulated sunlight of AMI (length of sunlight passing through the atmosphere) 1.5 and 100 mW / cm ² , the short-circuit current J _z was 13.5 mA / cm ² and the open circuit voltage The _VDC was 0.55 V, the FF (fill factor) was 0.7, and the conversion efficiency was 5.2%.

For comparison, a power generation cell using a paste having the same particle diameter as that of the above powder was prepared by using a conventional method (a: TiO ₂ paste coating-firing-dye dyeing / drying, b: solid electrolyte coating / drying at the counter electrode, a The power generation cell is obtained by combining the process and the process b), and the conversion efficiency of this manufactured product is 2 to 3%. That is, it was confirmed that it is more effective to use the film forming method according to the present invention.

  As described above, the film forming method according to the present invention has been described in the case where a power generation cell of a dye-sensitized solar cell is manufactured. However, as in this time, powders such as ceramic, metal, and polymer are laminated. It can also be applied to the production of functional parts and products, that is, functional devices.

  By the way, in the first embodiment, it has been described that the film formation is performed with the inside of the container under a predetermined degree of vacuum. However, the film formation can be performed in the air, and the high-frequency coil is disposed on the outer periphery of the container. Although it has been described that plasma is generated inside, it is not necessary to generate plasma.

  In the first embodiment, a conductive adhesive is applied to the surface of the substrate so that the powder easily adheres. For example, as shown in FIG. You may make it arrange | position 21 with the directionality (orientation) (for example, so that a string may hang down).

  By doing so, the powder P becomes entangled with the carbon nanotubes 21 and easily adheres to the substrate K, and is also located between the powder P and the substrate K and has a function as a current collector. Can do. In this sense, the carbon nanotube 21 exhibits an adhesion function and a current collecting function.

  In some cases, the film itself has a current collecting function (function as a current collector) by mixing the carbon nanotubes with the powder P placed on the lower electrode 7 in the first embodiment. May be.

Further, as shown in FIG. 3, the particle size (size) of the powder P to be adhered to the substrate K by forming a large number of holes having a predetermined diameter between the upper electrode 5 and the lower electrode 7 in the first embodiment. A particle size control plate (also referred to as a powder size control plate) 31 for controlling the particle size may be disposed. That is, only the powder P having a predetermined diameter or less can be attached to the substrate K by the particle size control plate 31. As the particle size control plate 31, for example, a mesh plate made of metal (such as copper) or synthetic resin (such as polytetrafluoroethylene) is used. However, when the particle size control plate 31 is made of metal, the distance between the particle size control plate 31 and the upper electrode 5 and the lower electrode 7 or a value at which the applied voltage does not cause dielectric breakdown (does not discharge). Has been.
[Embodiment 2]
Next, a film forming apparatus and a film forming method according to Embodiment 2 of the present invention will be described.

  In the first embodiment, the film is formed on one substrate. However, in the second embodiment, two substrates can be arranged in one container to perform film formation. It is what I did. Here, the same constituent members as those in the first embodiment will be described with the same member numbers.

  That is, as shown in FIG. 4, a rotary table 41 that is rotated by a motor or the like is disposed in the lower part of the container (not shown in FIG. 4), and at least 180 degrees symmetrical to the rotary table 41. The lower electrode 7 is disposed via the electrode holding member 6 and the upper electrode 5 is disposed above one of the lower electrodes 7. The lower electrode 7 may be provided directly on the turntable 41 without providing the electrode holding member 6. Of course, in this case, on the rotary table 41 side, an annular edge is projected so that the powder P does not move outward (does not spill).

  When film formation is performed with this configuration, different types of powders P1 and P2 are placed on the respective lower electrodes 7, and between the upper electrode 5 and the lower electrode 7 facing the upper electrode 5. A high-voltage DC voltage is applied to form a thin film of powder P1 on the substrate K.

  Next, the substrate K on the upper electrode 5 side is replaced, and the rotary table 41 is rotated 180 degrees so that the lower electrode 7 on which the powder P2 of a different type from the previous one is placed is placed at a position facing the upper electrode 5. Move to perform film formation.

According to this configuration, different types of thin films can be formed on different substrates with one film forming apparatus.
Further, by changing the substrate K held on the upper electrode 5 and rotating only the rotary table 41 and sequentially forming the two lower electrodes 7 to face each other, different types of powders (materials) are formed. ) Can be stacked on the surface of one substrate K.
[Embodiment 3]
Next, a film forming apparatus and a film forming method according to Embodiment 3 of the present invention will be described.

  In the first embodiment, the film is formed on one substrate. However, in the third embodiment, two substrates are arranged in one container and formed on each substrate. In addition, the thickness of one thin film can be measured, and when the film thickness of one substrate is measured, the other substrate can be formed. Here, the same constituent members as those in the first embodiment will be described with the same member numbers.

  That is, as shown in FIG. 5, in the container (not shown in FIG. 5), the electrode holding member 51 is reciprocated by a moving device (not shown) in a predetermined direction (horizontal direction) above the lower electrode 7. The electrode holding member 51 is arranged so as to be movable, and the two upper electrodes 5 are separated from each other in the moving direction, and each upper electrode 5 moved to the outside of the cylindrical body 4 by the electrode holding member 51. A film thickness meter 52 is disposed at a lower position facing the substrates K1 and K2.

When film formation is performed with this configuration, first, one upper electrode 5 is moved onto the lower electrode 7 and film formation is performed on the substrate K1.
When this film formation is performed to some extent, the electrode holding member 51 is moved in a predetermined direction to move the one substrate K1 to the outside of the cylindrical body 4, and the substrate K1 is measured by the film thickness meter 52 disposed therebelow. The thickness of the thin film formed on is measured.

  During this measurement, since the substrate K2 held by the other upper electrode 5 is moved onto the lower electrode 7, film formation is performed on the other substrate K2. If the film thickness of the one substrate 1 is a predetermined value, after the substrate K1 is replaced with a new one, and the film formation on the other substrate K2 is completed, the electrode holding member 51 is moved in the opposite direction, Film formation may be performed on a new substrate. When the film thickness of one substrate 1 is insufficient, as soon as the film formation on the other substrate K2 is completed, the electrode holding member 51 is moved in the reverse direction and again with respect to the one substrate K1. It is sufficient to form the film only for the insufficient film thickness.

  In this way, the thickness of the thin film formed on the surface of one substrate K1 can be measured, and even during this measurement, film formation can be performed on the other substrate K2. The working efficiency of the membrane is good.

  In Embodiment 3 described above, when the upper electrode is moved, that is, when the substrate is moved, a thin film (on the substrate) is arranged by arranging a roller capable of pressing the surface of the substrate. (Powder) can be pressed against the substrate to strengthen its adhesion. Further, if a heater is built in the pressing roller, the adhesion can be made stronger.

It is sectional drawing which shows schematic structure of the film-forming apparatus which concerns on Embodiment 1 of this invention. It is principal part sectional drawing which shows the modification of the film-forming apparatus. It is a schematic sectional drawing which shows the modification of the film-forming apparatus. It is sectional drawing which shows schematic structure of the film-forming apparatus which concerns on Embodiment 2 of this invention. It is sectional drawing which shows schematic structure of the film-forming apparatus which concerns on Embodiment 3 of this invention.

Explanation of symbols

K substrate P powder 1 vacuum pump 2 air discharge pipe 3 container 4 cylinder 5 upper electrode 6 electrode holding member 7 lower electrode 8 DC power supply 10 high frequency coil 11 heater 12 heater 13 inert gas supply pipe 21 carbon nanotube 31 particle size control Plate 41 Rotary table 51 Electrode holding member 52 Film thickness meter

Claims (9)

An electrostatic field is formed between the two electrodes by applying a DC voltage between one electrode holding the substrate on which the film is formed and the other electrode on which the powder material is placed. ,
A film forming method comprising: forming a film by reciprocating a powder, which is the film material, between two electrodes by an electric field generated in the electrostatic field, and attaching the powder to a substrate surface.   The film forming method according to claim 1, wherein the film forming is performed under vacuum.   The film forming method according to claim 1, wherein a substrate having a conductive material provided on a surface thereof is used.   4. The film forming method according to claim 3, wherein a carbon nanotube or an adhesive is used as the conductive material provided on the substrate surface.   The film forming method according to claim 1, wherein carbon nanotubes are mixed in the film material.   The film forming method according to any one of claims 1 to 5, wherein plasma is generated in a space region between both electrodes and ions are applied to the surface of the powder to be activated. A film forming apparatus for depositing powder on the surface of a substrate to form a film,
A DC voltage is applied between the upper electrode disposed in the upper part of the container and capable of holding the substrate, the lower electrode disposed under the upper electrode in the container and capable of mounting powder, and the two electrodes. DC power supply,
And when performing film formation,
A DC voltage is applied between the two electrodes to form an electrostatic field, and a Coulomb force is applied to the powder placed on the lower electrode by the electric field generated in the electrostatic field to cause the powder to flow between the two electrodes. A film forming apparatus characterized in that powder is adhered to the surface of a substrate by reciprocating.   8. The film forming apparatus according to claim 7, further comprising a plasma generator for generating plasma in a space region between at least both electrodes in the container.   9. The film forming apparatus according to claim 7, wherein a particle size control plate for controlling the size of the powder moving from the lower electrode to the substrate side is disposed between both electrodes.

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