JP2009059515A - Forming method of conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration of a resin part even if the resin part exists on the surface of a substrate by controlling oxygen concentration in a film-forming device and suppress occurrence of a large interface resistance between the conductive substrate and a conductive film when they are electrically connected. <P>SOLUTION: This is a formation method of a conductive film to form the conductive film by a spray thermal decomposition method on the surface of a substrate 18, and sprays particulates of a material solution on the surface of the heated substrate in a film-forming device using an atmospheric gas of which the oxygen concentration is 2 vol% or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a conductive film forming method for forming a conductive film on a substrate by spray pyrolysis.

As a method for forming a conductive film such as an ITO film, there are conventional methods such as a sputtering method, a spray pyrolysis method, a vapor deposition method, and a sol-gel method, but a sputtering method is mainly used for forming a low resistance conductive film. Has been used. However, in recent years, a method for forming a low-resistance ITO film by spray pyrolysis has been developed (see, for example, Non-Patent Document 1). According to the method described in Non-Patent Document 1, an ITO film having a specific resistance of 1.9 × 10 ⁻⁴ Ωcm is obtained, and a film of 7.1 × 10 ⁻⁵ Ωcm is obtained by heat treatment. Therefore, the spray pyrolysis method is advantageous in that a conductive film having desirable characteristics can be obtained and the conductive film can be formed by a simple method, and various applications are expected.

  The spray pyrolysis method is a method of forming a conductive film or the like on the surface of a substrate by heating the substrate and spraying a raw material solution onto the substrate. An example of a conventional spray pyrolysis method is shown in FIG. 2 (see Non-Patent Document 2). In this method, a raw material is introduced from a raw material inlet 2 in one of the furnace bodies 1, the raw material is sprayed onto a substrate 4 that is heated in contact with a hot plate 3, and a conductive film is formed on the surface of the substrate 4. Form a film. In FIG. 2, 5 is the other port for discharging the atmospheric gas in the furnace body 1.

  Another example is shown in FIG. 3 (see Non-Patent Document 3). In this example, the raw material 7 sprayed from the spray nozzle 6 outside the film forming apparatus 10 is sprayed onto the heated substrate 9 placed on the hot plate 8 to form a film on the surface of the substrate 9. Be filmed. In FIG. 3, 11 is a tank for the raw material 7.

Another example is shown in FIG. 4 (see Patent Document 1). In this example, an apparatus in which an air supply pipe 12 for sending pressurized gas is added to the configuration of FIG. 3 is used, and the raw material supply pipe and pressurized gas (such as argon gas) are mixed to atomize the solution of the raw material 7. By spraying on the substrate, a conductive film is formed on the surface of the substrate 9.
JP 2004-167394 A “New development of transparent conductive film II” supervised by Yutaka Sawada, CMC Publishing (2002) Takao Nagatomo, Osamu Omoto, “Electrical and Optical Properties of Indium Oxide Films by Spray Method”, Applied Physics, Japan, 1978, 47, 7, p.618-623 TMRatcheva, MDNanova, LVVassilev, MGMikhailov, Properties of In2O3: Te films prepared by spraying method, Thin Solid Films, The Netherlands, Elsevier Sequoia, 1986, 139, p.189-199

  However, in the film forming apparatus using the spray pyrolysis method as shown in FIGS. 2, 3, and 4, when the resin portion is present on a part or all of the surface of the substrate, the substrate is heated and the substrate is heated. Since oxygen is contained in the surrounding atmosphere gas, there has been a problem that the resin deteriorates due to an oxidation reaction.

  Further, in the conventional film formation method by the spray pyrolysis method, a pressurized gas for atomizing the solution of the raw material 7 is used as in the example of FIG. 4, or the mist of the raw material is used as a substrate as in the example of FIG. Nitrogen gas is used as a carrier gas for transporting to the vicinity of 4, but the mist after reaching the surface of the substrate is exhausted and taken out of the film forming apparatus. This is in order to suppress ignition due to adhesion of fog in the film forming apparatus and retention of gas of a high concentration organic solvent. However, this exhaust makes it extremely difficult to control the oxygen concentration in the ambient gas around the substrate, and as a result, the resin portion deteriorates when there is a resin portion on the surface of the substrate.

Further, when the substrate is a conductive substrate and the substrate and the conductive film are electrically connected, if there is a resin portion on the surface of the substrate, the resin portion is derived between the substrate and the conductive film. There was a problem that a large resistance was generated and a good electrical connection could not be obtained. For example, in an electronic device (specifically, a photoelectric conversion device) as shown in FIG. 5, when the conductive film 15 is to be formed by a conventional spray pyrolysis method, the conductive substrate 13 and the conductive film 15 In the meantime, the interface resistance derived from the resin part 14 occurs. The interface resistance between the conductive substrate and the conductive film is about 15Ω per 1 cm ² of the contact area, and there is a problem that the performance required for the electronic device cannot be obtained.

  The problem that a large resistance derived from the resin portion is generated between the substrate and the conductive film is presumed to be caused by the following mechanism. That is, although the mechanism is not clearly understood, the surface of the resin part is exposed to a temperature of 300 ° C. or higher and the solvent of the gasified raw material solution during film formation, and the decomposition product becomes conductive with the substrate. It is presumed that the cause of the increase in resistance is that a contamination layer is formed between the films, and the decomposition products deteriorate the film quality of the conductive film.

  Therefore, the present invention has been completed in view of the above-mentioned conventional problems, and the purpose thereof is to suppress the deterioration of the resin part even if the resin part exists on the surface of the substrate, In the case where the conductive substrate and the conductive film are electrically connected, it is possible to suppress the occurrence of a large interface resistance between them.

  The method for forming a conductive film of the present invention is a method for forming a conductive film by forming a conductive film on the surface of a substrate having a resin portion on the surface by a spray pyrolysis method, wherein the oxygen concentration is 2% by volume or less. The fine particles of the raw material solution are sprayed on the surface of the substrate heated in the film forming apparatus using the atmospheric gas.

  In the method for forming a conductive film of the present invention, preferably, the conductive film is an ITO film, and the oxygen concentration in the atmospheric gas is 0.3% by volume to 2% by volume. Is.

  In the method for forming a conductive film of the present invention, it is preferable that the substrate has a large number of spherical first-conductivity-type crystalline semiconductor particles in which a second-conductivity-type semiconductor portion is formed on a surface layer on the conductive substrate. A substrate for a photoelectric conversion device in which an insulating layer made of a resin is formed on the conductive substrate between the crystal semiconductor particles, and the conductive film is formed on the semiconductor portion and the insulating layer. It is characterized by forming.

  The method for forming a conductive film of the present invention is a method for forming a conductive film by forming a conductive film on the surface of a substrate having a resin portion on the surface by a spray pyrolysis method, wherein the oxygen concentration is 2% by volume or less. Since the fine particles of the raw material solution are sprayed on the surface of the heated substrate in the film forming apparatus using the atmospheric gas, the resin portion is deteriorated by oxygen even if the resin portion exists on the surface of the substrate. Can be suppressed. In addition, since the oxygen concentration is 2% by volume or less, deterioration due to oxidation of the substrate itself and each part in the film forming apparatus can be suppressed. Furthermore, when the conductive substrate and the conductive film are electrically connected, the resin portion is hardly deteriorated by oxygen, so that the generation of a large interface resistance between the conductive substrate and the conductive film is suppressed. can do.

  Therefore, since the substrate has a resin portion on the surface, an electronic element or the like having a resin portion with extremely small deterioration can be manufactured. That is, an electronic device having a resin part as a conductive film, an insulator, and the like, an electronic product such as an electric circuit and a photoelectric conversion device, and an electric product can be manufactured with extremely small deterioration of the resin part.

  In the method for forming a conductive film of the present invention, preferably, the conductive film is an ITO film, and the oxygen concentration in the atmospheric gas is 0.3 volume% to 2 volume%. In the case of an ITO film which is a physical conductive film, if the oxygen concentration in the atmospheric gas is less than 0.3% by volume, the resistance of the conductive film will increase. An increase in resistance can be effectively suppressed.

  In the method for forming a conductive film of the present invention, it is preferable that the substrate has a large number of spherical first-conductivity-type crystalline semiconductor particles in which a second-conductivity-type semiconductor portion is formed on the surface of the conductive substrate. It is a substrate for a photoelectric conversion device in which an insulating layer made of a resin is formed on a conductive substrate between crystal semiconductor particles, and since a conductive film is formed on a semiconductor portion and an insulating layer, a crystal When the semiconductor particles and the conductive substrate are electrically connected to the conductive film, the insulating layer made of the resin is hardly deteriorated by oxygen, so that there is a large interface resistance between the crystalline semiconductor particles and the conductive film. It can be suppressed from occurring. As a result, a photoelectric conversion device having high photoelectric conversion efficiency can be obtained.

  Hereinafter, the method for forming a conductive film of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of a film forming apparatus used in the method for forming a conductive film of the present invention. In FIG. 1, a substrate 18 is placed on the upper surface of a holder 17 in a film forming chamber 16 of the film forming apparatus. The lower surface of the holder 17 faces the hot plate 19 through a space. The heating of the hot plate 19 is controlled by the power source and the control device 20. A spray nozzle 21 for spraying the raw material solution is connected to a raw material solution tank 22 via a raw material solution supply pipe. The pressure of the raw material solution is controlled by the pressure control device 23 to control the pressure of the spray from the spray nozzle 21, the spray amount, the spray speed (flow rate of the raw material solution), and the like.

  In FIG. 1, 31 is a nitrogen gas supply pipe, and 32 is an air supply pipe.

  The method for forming a conductive film of the present invention is a method for forming a conductive film on the surface of the substrate 18 by spray pyrolysis, and uses an atmospheric gas having an oxygen concentration of 2% by volume or less. The raw material solution fine particles are sprayed on the surface of the substrate 18 heated in the film forming apparatus.

  The material of the substrate 18 is a conductive material such as aluminum, stainless steel, or silicon, or a semiconductor material, or an insulating material such as aluminum oxide or glass.

The conductive film is made of an ITO film, a SnO ₂ film, a ZnO film, or the like.

  The pressure of the spray by the spray pyrolysis method is preferably 0.2 MPa to 1 MPa. If it is less than 0.2 MPa, the sprayed raw material solution does not become mist (fine particles), and liquid sag is likely to occur. If the pressure exceeds 1 MPa, the piping structure is likely to become complicated in order to increase the pressure resistance of the piping.

  The spray amount is preferably 0.3 g / sec (gram / second) to 0.8 g / sec. If it is less than 0.3 g / sec, the sprayed fine particles of the raw material solution are disturbed by the ascending air current caused by the hot plate 19 and hardly reach the substrate 18. When it exceeds 0.8 g / sec, the raw material that has reached the substrate 18 takes the heat of the surface of the substrate 18, the temperature of the substrate 18 is lowered, and the film formation reaction due to thermal decomposition tends to be incomplete.

  The spray speed of the raw material solution discharged from the spray nozzle 21 (flow rate of the raw material solution) is preferably 1 m / sec (meter / second) to 10 m / sec. If it is less than 1 m / sec, the sprayed fine particles of the raw material solution are disturbed by the rising air flow caused by the hot plate 19 and are difficult to reach the substrate 18. If it exceeds 10 m / sec, the mist of the raw material solution that has reached the substrate 18 takes the heat of the surface of the substrate 18, and the temperature of the substrate 18 is lowered and the film formation reaction due to thermal decomposition tends to be incomplete.

  The temperature of the raw material solution discharged from the spray nozzle 21 is preferably about 0 ° C to 75 ° C. When the temperature is lower than 0 ° C., moisture in the chamber (film formation chamber) or in the air tends to condense in the piping. When it exceeds 75 ° C., the solvent in the raw material solution is easily vaporized in the pipe, or is easily vaporized immediately after spraying.

  The average particle diameter of the fine particles of the raw material solution discharged from the spray nozzle 21 is preferably about 20 μm to 80 μm. If it is less than 20 μm, the solvent in the raw material solution is easily vaporized immediately after spraying. When the thickness exceeds 80 μm, the diameter of the fine particles of the raw material solution when reaching the substrate 18 is large, so that the film formation reaction due to thermal decomposition tends to be incomplete.

  The raw material solution contains water, alcohol such as ethyl alcohol, indium chloride, tin chloride, and the like, which are raw material components of the conductive film.

  The atmospheric gas is an inert gas such as nitrogen gas or argon gas, or an oxygen mixed gas of oxygen gas and nitrogen gas.

  The oxygen concentration in the film forming chamber 16 can be measured by an oxygen concentration meter, and based on the measurement result, the oxygen concentration can be controlled by the amount of nitrogen gas and air supplied into the film forming chamber 16. Nitrogen gas can be supplied into the film forming chamber 16 through the nitrogen gas supply pipe 31, and air can be supplied into the film forming chamber 16 through the air supply pipe 32.

  The heating temperature of the substrate 18 is preferably about 300 ° C to 600 ° C. If it is less than 300 degreeC, the film formation reaction by thermal decomposition tends to become incomplete. When the temperature exceeds 600 ° C., the film formation reaction due to thermal decomposition tends to proceed before the raw material solution reaches the substrate 18.

  In the method for forming a conductive film of the present invention, the conductive film is preferably an ITO film, and the oxygen concentration in the atmospheric gas is preferably 0.3% by volume to 2% by volume. When the conductive film is an ITO film that is an oxide conductive film, if the oxygen concentration in the atmospheric gas is less than 0.3% by volume, the resistance of the conductive film increases. An increase in resistance of the conductive film formed can be effectively suppressed.

  In the method for forming a conductive film of the present invention, the substrate 18 has a resin portion on the surface. Accordingly, it is possible to manufacture an electronic element or the like having a resin portion with extremely little deterioration. That is, an electronic device having a resin part as a conductive film, an insulator, and the like, an electronic product such as an electric circuit and a photoelectric conversion device, and an electric product can be manufactured with extremely small deterioration of the resin part.

  The resin portion on the surface of the substrate 18 is made of polyimide or the like. Since the heating temperature of the substrate 18 is about 300 ° C. to 600 ° C., the resin portion is preferably made of a heat-resistant resin, and in addition to polyimide, polyethersulfone, polyetheretherketone, polyamideimide and the like are preferable.

  In the method for forming a conductive film of the present invention, there is a portion surrounded by a resin portion on the surface of the conductive substrate 18, and the surface of the substrate 18 and the conductive film are electrically connected at that portion. It is preferable to apply. Since the portion surrounded by the resin portion is greatly affected by deterioration due to oxidation of the resin, the interface resistance is likely to increase. Therefore, the formation method of the present invention that can form a conductive film while suppressing oxidation of the resin can be suitably applied. The configuration in which a resin layer is provided on the surface of the conductive substrate 18, a through conductor such as a via conductor is formed on the resin layer, and the through conductor and the conductive film are connected to each other for the same reason as described above. The formation method of the invention can be suitably applied.

  Further, according to the method for forming a conductive film of the present invention, as shown in FIG. 8, the substrate 18 has a second conductive type (for example, n-type) semiconductor portion 43 formed on the conductive substrate 41 as a surface layer. A large number of crystalline semiconductor particles 42 made of spherical first conductivity type (for example, p-type) silicon are joined together, and an insulating layer 44 made of resin is formed on the conductive substrate 41 between the crystalline semiconductor particles 42. A conductive film 45 is preferably formed on the semiconductor portion 43 and the insulating layer 44 as a substrate for the conversion device. In this case, when the crystalline semiconductor particles 42 and the conductive substrate 41 are electrically connected to the conductive film 45, the insulating layer 44 made of a resin is hardly deteriorated by oxygen. Generation of a large interface resistance between the film 45 and the film 45 can be suppressed. As a result, a photoelectric conversion device having high photoelectric conversion efficiency can be obtained.

  As described above, when the substrate 18 is a substrate for a photoelectric conversion device, the conductive substrate 41 is made of aluminum or the like, and the second conductivity type (for example, n-type) semiconductor portion 43 is phosphorus (P) or the like as an n-type dopant. Is included. The crystalline semiconductor particles 42 made of spherical first conductivity type (for example, p-type) silicon have a diameter of about 100 to 1000 μm and contain boron (B) or the like as a p-type dopant. The insulating layer 44 made of resin is made of polyimide or the like. The photoelectric conversion device is used as a solar cell or the like.

  Examples of the method for forming a conductive film of the present invention will be described below.

First, as a raw material solution used for the spray pyrolysis method, a solution in which indium chloride and tin chloride were completely dissolved in ethyl alcohol and water was used. Indium chloride and tin chloride were adjusted to have a metal ion concentration of 0.05 mol / l (mol / liter) (1 liter = 1000 cm ³ ). For indium and tin, the ratio of tin to indium was 7% by weight.

Further, a substrate made of square silicon having a size of 50 mm × 50 mm was used as the substrate, and a resin made of polyimide was applied to the surface of the substrate, followed by baking at 400 ° C. This resin layer was formed with a square window with an area of 1 cm ² , and the surface of the substrate was exposed inside the window. Before forming the conductive film, the substrate was immersed in a hydrofluoric acid solution to remove the silicon oxide film on the surface of the substrate.

  Next, a PID control type using a spray pyrolysis film forming apparatus in which a holder for setting the substrate is provided in the film forming chamber and an explosion-proof hot plate for heating the substrate is provided below the holder. The temperature of the hot plate was controlled by the temperature controller, and the substrate surface was heated to 350 ° C.

  Next, the oxygen concentration in the atmospheric gas in the film forming chamber of the film forming apparatus using the spray pyrolysis method becomes 0%, 1%, 2%, 2.5%, 5%, and 20% (see FIG. 6). Then, nitrogen gas and air were introduced into the film formation chamber, and after waiting for 30 seconds or more when the oxygen concentration reached a predetermined ratio, the oxygen concentration was stabilized, and then the substrate was placed on the holder.

  Next, the raw material solution was sprayed from the spray nozzle at intervals of 15 seconds for 0.5 seconds, and the discharge amount during spraying was sprayed to the surface of the substrate at 0.3 g / sec. The average particle size of the fine particles of the sprayed raw material solution was about 45 μm. An ITO film having a thickness of 0.1 μm was formed by spraying 50 times, and the substrate was removed from the hot plate to complete the film formation.

  Next, the interface resistance between the ITO film and the surface of the substrate was measured with a DC voltage power source and a DC current monitor. As a result, as shown in FIG. 6, when the oxygen concentration is 0%, 1%, 2%, and 2.5%, the interface resistance is 1Ω, and when the oxygen concentration is 5%, the interface resistance is 10Ω and the oxygen concentration is The interface resistance was 15Ω at 20%.

  The oxygen concentration in the atmosphere gas in the film forming chamber is 0%, 0.2%, 0.3%, 0.7%, 1%, 3%, 5% (see FIG. 7). In the same manner as in Example 1, an ITO film was formed.

Then, when measured with a DC voltage power source and a DC current monitor between the ITO film and the surface of the substrate, as shown in FIG. 7, when the oxygen concentration is 0%, the resistivity of the ITO film is 2.8 × 10 ³ , When the oxygen concentration is 0.2%, the resistivity of the ITO film is 2.4 × 10 ³ , and when the oxygen concentration is 0.3%, the resistivity of the ITO film is 1.4 × 10 ³ and the oxygen concentration is 0 The specific resistance of the ITO film is 1.2 × 10 ³ when 0.7%, the specific resistance of the ITO film is 1.1 × 10 ³ when the oxygen concentration is 1%, and the ITO film when the oxygen concentration is 3%. When the specific resistance of the ITO film was 1.2 × 10 ³ and the oxygen concentration was 5%, the specific resistance of the ITO film was 1.1 × 10 ³ .

  As shown in FIG. 7, it was found that the resistance of the ITO film increases when the oxygen concentration is less than 0.3%.

It is typical sectional drawing of the film-forming apparatus used for the formation method of the electroconductive film of this invention. It is typical sectional drawing which shows an example of the conventional film-forming apparatus. It is typical sectional drawing which shows the other example of the conventional film-forming apparatus. It is typical sectional drawing which shows the other example of the conventional film-forming apparatus. It is typical sectional drawing of the board | substrate which has an electroconductive film and a resin part. It is a graph which shows the relationship between the oxygen concentration in atmospheric gas in a film-forming apparatus, and the interface resistance of a board | substrate and a conductive film. It is a graph which shows the relationship between the oxygen concentration in atmospheric gas in a film-forming apparatus, and the specific resistance of an electroconductive film. It is sectional drawing of a board | substrate in case a board | substrate is a board | substrate for photoelectric conversion apparatuses of this invention.

Explanation of symbols

16: Film formation chamber 17: Holder 18: Substrate 19: Hot plate 21: Spray nozzle 22: Raw material solution tank 23: Raw material solution pressure control device 41: Conductive substrate 42: Crystalline semiconductor particles 43: Semiconductor part 44: Insulation Layer 45: conductive film

Claims (3)

  A conductive film forming method for forming a conductive film on the surface of a substrate having a resin portion on a surface by a spray pyrolysis method, wherein an atmosphere gas having an oxygen concentration of 2% by volume or less is used. A method for forming a conductive film, comprising spraying fine particles of a raw material solution onto the surface of the substrate heated in step (1).   The method for forming a conductive film according to claim 1, wherein the conductive film is an ITO film, and the oxygen concentration in the atmospheric gas is 0.3 vol% to 2 vol%.   The substrate includes a plurality of spherical first-conductivity-type crystalline semiconductor particles each having a second-conductivity-type semiconductor portion formed on a surface layer, and a plurality of spherical first-conductivity-type crystal semiconductor particles bonded to the substrate. The conductive film according to claim 1, wherein the conductive film is formed on the semiconductor portion and the insulating layer. Of forming a conductive film.

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