JP5048862B1 - Film formation method on glass substrate - Google Patents

Abstract

A high-quality film is formed by suppressing the occurrence of cracking and warping of a glass substrate.
A first composition for forming a first film by spraying an aqueous solution containing an oxide precursor as a solute on a glass substrate at a first heating temperature of 300 ° C. or higher and lower than a strain point of glass. A film forming step and a second film forming step of forming a second layer film by spraying an aqueous solution containing an oxide precursor as a solute on a glass substrate at a second heating temperature higher than the first heating temperature. Prepare. In addition, after the second film forming step, a strain removing step of holding the glass substrate at a temperature equal to or higher than the annealing point of the glass, and a slow cooling step of gradually cooling the glass substrate to room temperature after the strain removing step are provided. .
[Selection] Figure 2

Description

  The present invention relates to a film forming method on a glass substrate.

  Transparent conductive films are widely used in fields such as semiconductors, displays, and solar cells. As the transparent conductive film, those made of metal oxides such as STO (strontium titanate) and ITO (Sn-doped indium oxide) are mainly used. The transparent conductive film is generally formed using a sputtering method, a vapor deposition method, a metal organic chemical vapor deposition method using an organic metal compound, or the like.

  In the sputtering method and the vapor deposition method, since a film is formed by a vacuum process, an equipment for forming and maintaining a vacuum atmosphere such as a vacuum vessel is required. In the organometallic chemical vapor deposition method, since the organometallic compound used as a raw material has explosiveness and toxicity, a highly confidential facility is required. For this reason, in order to perform the film forming method described above, an expensive film forming apparatus is required.

  Therefore, a mist method has been proposed as a film forming method different from the conventional one. The mist method is a method of forming a film by atomizing a solution containing a raw material metal as a solute and spraying it on a substrate.

  In the mist method, a film can be formed at atmospheric pressure, so that no manufacturing equipment such as a vacuum vessel and pumps is required. In addition, since a dangerous substance such as an organometallic compound is not used in the mist method, an inexpensive film forming apparatus with a simple configuration can be used.

  JP-A-2007-77433 (Patent Document 1) is a prior document disclosing a film forming apparatus for forming a thin film on a target object by spray pyrolysis. In the film forming apparatus described in Patent Document 1, the raw material solution is sprayed from the discharge means toward the pretreatment chamber for heating the object to be processed to a predetermined temperature and the object to be processed that is maintained at the predetermined temperature. Thus, a film forming chamber for forming a thin film on the object to be processed and a post-processing chamber for cooling the object to be processed on which the thin film is formed to a predetermined temperature are provided.

JP 2007-77433 A

  When a thin film is formed on a glass substrate by a mist method or a spray pyrolysis method, the glass substrate may be cracked or warped due to internal strain due to heat history of heating and cooling. When the glass substrate is cracked or warped, the film properties of the thin film formed on the glass substrate are deteriorated. In a thin film solar cell, the power generation efficiency of the solar cell decreases when the film properties of the thin film decrease.

  The present invention has been made in view of the above problems, and provides a method for forming a film on a glass substrate, which can form a high-quality film while suppressing the occurrence of cracking and warping of the glass substrate. For the purpose.

  The method for forming a film on a glass substrate according to the present invention comprises spraying an aqueous solution containing an oxide precursor as a solute onto a glass substrate at a first heating temperature of 300 ° C. or higher and lower than the strain point of glass. A second layer film is formed by spraying an aqueous solution containing an oxide precursor as a solute on a glass substrate under a first film forming step for forming a layer film and a second heating temperature higher than the first heating temperature. A second film forming step of forming In addition, the method for forming a film on the glass substrate includes a strain removing step for holding the glass substrate at a temperature equal to or higher than the annealing point of the glass after the second film forming step, and a glass substrate at room temperature after the strain removing step. And a slow cooling step of slowly cooling to a low temperature.

In one form of the invention, the second heating temperature is lower than the strain point of the glass.
In one form of this invention, the 2nd heating temperature is more than the annealing point of glass.

  Preferably, in the slow cooling step, cooling is performed so that the temperature of the glass substrate decreases at a rate of 5 ° C./min to 30 ° C./min.

  In one embodiment of the present invention, the first layer film is a barrier layer that suppresses migration of alkali metal ions from the glass substrate, and the second layer film is a transparent conductive film.

In one embodiment of the present invention, the first layer film is made of Al ₂ O ₃ , the first heating temperature is 350 ° C. or higher and lower than 480 ° C., and the second layer film is SnO doped with fluorine. ₂ and the second heating temperature is not less than 550 ° C. and not more than 600 ° C.

  In one embodiment of the present invention, the method for forming a film on a glass substrate further includes a third film forming step between the second film forming step and the strain removing step. In the third film forming step, an aqueous solution containing the oxide precursor as a solute is sprayed on the glass substrate at a third heating temperature higher than the second heating temperature to form a third layer film. The first film is a prism layer, the second film is a barrier layer that suppresses migration of alkali metal ions from the glass substrate, and the third film is a transparent conductive film. .

In one embodiment of the present invention, the first layer film is made of TiO ₂ , the first heating temperature is 300 ° C. or higher and lower than 400 ° C., and the second layer film is made of Al ₂ O ₃ or MgO. The second heating temperature is 350 ° C. or higher and lower than 480 ° C., the third layer film is made of SnO ₂ doped with fluorine, and the third heating temperature is 550 ° C. or higher and 600 ° C. or lower.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the crack and curvature of a glass substrate can be suppressed, and a high quality film | membrane can be formed on a glass substrate.

It is a side view which shows the structure of the film-forming apparatus used for the film-forming method to the glass base material concerning Embodiment 1 of this invention. It is sectional drawing which shows the structure of the film-forming chamber contained in the film-forming apparatus which concerns on the embodiment. It is the figure which looked at the film-forming chamber of FIG. 2 from the arrow III direction. It is a figure which shows the temperature profile of the board | substrate in the film-forming method to the glass base material which concerns on the same embodiment. 3 is a graph showing measurement results of Example 1. It is a graph which shows the measurement result of a comparative example.

  First, the film-forming apparatus used for the film-forming method to the glass base material concerning Embodiment 1 of this invention is demonstrated. In the following description of the embodiments, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated. In the present embodiment, film formation of a transparent conductive film used for a thin film solar cell will be described as an example, but the present invention can be applied to film formation of various films on a glass substrate.

(Embodiment 1)
FIG. 1 is a side view showing a configuration of a film forming apparatus used in a film forming method on a glass substrate according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view showing a configuration of a film forming chamber included in the film forming apparatus according to the present embodiment. FIG. 3 is a view of the film forming chamber of FIG. 2 as viewed from the direction of arrow III. In FIG. 3, the spray mechanism is illustrated in a simplified manner.

  As shown in FIG. 1, a film forming apparatus 10 according to an embodiment of the present invention includes an input unit 11 into which a substrate 200 that is a glass base material is input, a preheating unit 12 in which the substrate 200 is preheated, and a substrate 200. It has the film-forming part 13 in which film-forming processing is carried out, the slow cooling part 14 in which the board | substrate 200 is cooled, and the taking-out part 15 from which the board | substrate 200 is taken out.

  As shown in FIGS. 1 to 3, the film forming apparatus 10 includes a transfer conveyor 110 that is a transfer unit that transfers the substrate 200 along the transfer path. The conveyor 110 is provided across the input unit 11, the preheating unit 12, the film forming unit 13, the slow cooling unit 14, and the takeout unit 15.

  The conveyor 110 includes a conveyor belt 111 on which the substrate 200 is placed, a pulley 112 around which the conveyor belt 111 is wound, a drive shaft 113 that drives the pulley 112, and a motor (not shown) that applies power to the drive shaft 113. It consists of and. The conveyor belt 111 is made of heat-resistant metal or resin.

  The substrate 200 is transported in the direction indicated by the arrow 114 by the transport conveyor 110. That is, in the film forming apparatus 10 according to the present embodiment, the transport path of the substrate 200 is linear in plan view. However, the conveyance path is not limited to a straight line, and the conveyance path may be bent in a plan view or may be a curved line.

  The film forming apparatus 10 includes a plurality of film forming chambers 100 (100a, 100b, 100c, 100d) positioned so as to be aligned in the transfer path. Specifically, a film formation chamber 100a, a film formation chamber 100b, a film formation chamber 100c, and a film formation chamber 100d are provided in this order from the upstream side in the transport direction of the substrate 200. In the present embodiment, four film formation chambers 100 (100a, 100b, 100c, and 100d) are provided, but a plurality of film formation chambers 100 may be provided.

  Further, the film formation apparatus 10 is positioned in a tunnel shape along the transfer path so as to connect adjacent film formation chambers among the plurality of film formation chambers 100, and the substrate 200 that sequentially passes through the plurality of film formation chambers 100. A heating furnace 120 is provided for surrounding and heating. As shown in FIG. 3, the lower portion of the housing 150 is covered with the heating furnace 120.

  An opening is provided in the upper part of the tunnel-shaped heating furnace 120, and a housing 150 is incorporated in the opening. The heating furnace 120 is provided over the four film formation chambers 100 (100a, 100b, 100c, 100d). The heating furnace 120 is provided from the upstream side of the film forming chamber 100 a located upstream in the transport direction of the substrate 200 in order to preheat the substrate 200. That is, the heating furnace 120 is provided across the preheating unit 12 and the film forming unit 13.

  The substrate 200 is heated while being transported through the heating furnace 120 by the transport conveyor 110. When the film is formed on the substrate 200, the inside of the heating furnace 120 is maintained at substantially the same temperature for each film forming chamber.

  The film forming chamber 100 according to the present embodiment is an apparatus that deposits a fine film forming material 160 on a substrate 200 to form a film. As shown in FIG. 2, the film formation chamber 100 includes a housing 150, a spray mechanism for spraying a film forming gas obtained by atomizing a film forming material 160 into the housing 150, and one side wall of the housing 150. And an exhaust port 152 for exhausting the film forming gas.

  As shown in FIG. 1, one end of a connection pipe 310 is connected to the exhaust port 152. The other end of the connection pipe 310 is connected to an abatement apparatus 300 that is a gas processing means for detoxifying the exhausted film forming gas.

  As shown in FIG. 2, the housing 150 has an inlet 151 into which the carrier gas 170 is introduced. The housing 150 also has a partition wall 154 that divides the interior of the housing 150 into three spaces. The first space is a spray mechanism arrangement space 158 in which a part of the spray mechanism is arranged. The second space is a film forming gas spray space 159 in which the film forming gas is sprayed from the spray mechanism. The third space is an exhaust space 153 connected to the exhaust port 152.

  The housing 150 has an open portion that faces the substrate 200 and allows the deposition gas to flow from the deposition gas spray space 159 onto the substrate 200. The opening part is formed in the lower part of the housing 150. As shown in FIGS. 1 and 3, the open portion is located in the heating furnace 120. A predetermined gap is provided between the substrate 200 being transported by the transport conveyor 110 and the open portion of the housing 150.

  The spray mechanism includes a tank 140 for storing a solution of the film forming material 160, a passage 141 through which compressed air introduced by a compressor (not shown) and the solution of the film forming material 160 are mixed, and a solution of the film forming material 160. And a spray nozzle 130 for atomizing as a film forming gas. An opening 155 is formed in the housing 150 corresponding to the position of the spray nozzle 130.

  A cooling jacket 131 which is a cooling means for cooling the spray nozzle 130 is attached to the end of the spray nozzle 130. The cooling jacket 131 is connected to a cooling water supply pipe (not shown), and the cooling water circulates inside the cooling jacket 131.

  Further, the spray mechanism includes a cylindrical rectifying member 132 attached to the tip of the spray nozzle 130. In the present embodiment, the rectifying member 132 has a tapered rectifying unit 134 that is located on the inner surface and rectifies the film forming gas. However, the shape of the rectifying unit 134 is not limited to this, and may have a trumpet shape, for example.

  The rectifying member 132 is attached to the cooling jacket 131 by connecting a connecting member (not shown) connected to a part of the outer surface of the rectifying member 132 to a part of the outer surface of the cooling jacket 131.

  The spray nozzle 130 is a two-fluid spray nozzle that mixes two fluids of a film forming material 160 and compressed air and sprays them in a mist form. Here, the mist means a state in which droplets having an average particle size of 0.1 μm or more and 100 μm or less are dispersed in a gas. The average particle diameter of the mist is a value calculated by the immersion method.

  However, the spraying mechanism is not limited to the spray nozzle 130, and a mist-like film forming gas may be generated using ultrasonic waves. When the mist-like film forming gas is generated by the ultrasonic vibrator, the average particle diameter of the mist can be made uniform compared to the case where the mist-like film forming gas is generated by the spray nozzle 130. Can be prevented from aggregating before reaching the substrate 200.

  As shown in FIG. 3, the plurality of spray nozzles 130 face the substrate 200 in the housing 150 and are arranged in a direction orthogonal to the transport direction of the substrate 200 at intervals. In FIG. 3, three spray nozzles 130 are arranged, but the number of spray nozzles 130 may be one or more.

  The number of spray nozzles 130 provided is the amount of film forming gas sprayed per unit time necessary to satisfy the desired tact time of the film forming process of the substrate 200, or the film forming necessary for performing the film forming process. It is changed appropriately according to the speed.

With respect to the distance L _h between the upper surface of the discharge port and the substrate 200 of the spray nozzle 130, the distance between the upper end and the substrate 200 of the furnace 120 is set to 1 / 4L _h.

  A part of the carrier gas 170 introduced from the inlet 151 described later is sent to the spray nozzle 130 in order to cool the spray nozzle 130. In order to send the carrier gas 170 to the spray nozzle 130, a cooling fan (not shown) is disposed in the vicinity of the spray nozzle 130. The spray nozzle 130 is air-cooled by a cooling fan. Further, the spray nozzle 130 is water cooled by the cooling jacket 131 described above.

  In this way, by cooling the vicinity of the spray nozzle 130, the solution of the film forming material 160 before being sprayed from the spray nozzle 130 is cooled to a temperature equal to or lower than the boiling point. More preferably, the solution of the film forming material 160 is cooled to about room temperature.

  By this cooling, since the solvent in the solution of the film forming material 160 can be prevented from volatilizing in the spray nozzle 130, the concentration of the solution of the film forming material 160 to be sprayed can be kept constant. Further, solidification of the film forming material 160 due to volatilization of the solvent in the solution of the film forming material 160 in the spray nozzle 130 can be suppressed.

  As a result, since the film can be formed using the film forming material 160 having a constant concentration, the quality of the film formed on the substrate 200 can be stabilized. Further, the clogging of the spray nozzle 130 due to the solidified film forming material 160 can be suppressed.

  As a solution of the film forming material 160, a solution in which a chloride of an inorganic material selected from the group consisting of zinc, tin, indium, cadmium, and strontium is dissolved in a solvent can be used. As the solvent, water, methanol, ethanol, butanol and the like can be used. As the solution of the film forming material 160, for example, an aqueous solution containing zinc acetate, an aqueous solution containing indium tin oxide, an aqueous solution containing tin oxide, or the like can be used.

  However, the solution of the film forming material 160 is not limited to this, and various solutions can be used. The concentration of the film forming material 160 solution is not particularly limited, and is, for example, a concentration of 0.1 mol / L or more and 3 mol / L or less.

  Here, the flow path of the gas in the housing 150 will be described. First, a carrier gas 170 made of, for example, compressed air is introduced into the film forming gas spray space 159 of the housing 150 from the introduction port 151. The carrier gas 170 introduced into the film forming gas spray space 159 flows in the direction indicated by the arrow 171. As the carrier gas 170, for example, nitrogen, oxygen, hydrogen, and a mixed gas thereof can be used.

  A mist film-forming gas is sprayed from the spray nozzle 130 into the spray region 162 in the direction indicated by the arrow 161. The mist film-forming gas and the carrier gas 170 are mixed with each other in the mixing region 181 to become mixed mist. The mixed mist flows in the direction indicated by the arrow 182 and reaches the open portion. The mixed mist is sprayed onto the main surface of the substrate 200 from the open portion. A region where the mixed mist containing the deposition gas is sprayed onto the substrate 200 is referred to as a spray region X.

  The mixed mist that has reached the spray region X flows along the main surface of the substrate 200. Specifically, the mixed mist flows in a direction indicated by an arrow 183 between a facing surface that is a part of the partition wall 154 and that faces the main surface of the substrate 200, and the main surface of the substrate 200. A region where the mixed mist flows in the direction indicated by the arrow 183 is referred to as a flow channel region Y.

  The mixed mist that has passed through the flow path region Y flows in the direction indicated by the arrow 184 in the exhaust space 153. A region where the mixed mist is directed from the main surface of the substrate to the exhaust port 152 is referred to as an exhaust region Z. The mixed mist that has passed through the exhaust space 153 and has reached the exhaust port 152 is rendered harmless by the detoxifying device 300 and discharged to the outside as the exhaust gas 180. In addition, in FIG. 2, the abatement apparatus 300 is not illustrated.

  The spray area X, the flow path area Y, and the exhaust area Z constitute an open portion. In each of the plurality of film forming chambers 100 (100a, 100b, 100c, 100d), the film forming gas flows from the spray mechanism through the open part toward the exhaust port 152.

  In the exhaust port 152, the mixed mist is exhausted at a flow rate that is about 3 to 10 times larger than the carrier gas 170 introduced from the introduction port 151. However, the flow rate of the introduced carrier gas 170 and the exhaust flow rate of the mixed mist are appropriately set. By appropriately setting the discharge pressure of the spray nozzle 130, the flow rate of the carrier gas 170, and the exhaust flow rate, the mixed mist can reach the upper surface of the substrate 200 stably.

  As shown in FIG. 1, a film forming gas flows in the film forming chamber 100a as indicated by an arrow 400. In the film forming chamber 100b, the film forming gas flows as indicated by an arrow 410. In the film forming chamber 100c, the film forming gas flows as indicated by an arrow 420. In the film forming chamber 100d, the film forming gas flows as indicated by an arrow 430.

  As described above, the substrate 200 passes through the vicinity of the open portion while the film forming gas is flowing, whereby the substrate 200 is formed. In the film forming apparatus 10 of the present embodiment, the transfer conveyor 110 is provided so that the substrate 200 passes through the vicinity of the open part.

  The substrate 200 is transferred by the transfer conveyor 110 so as to sequentially pass through the spray region X, the flow channel region Y, and the exhaust region Z in each of the plurality of film forming chambers 100 (100a, 100b, 100c, 100d). . The substrate 200 is formed by depositing fine particles of the film forming material 160 on the main surface while passing through the spray region X, the flow channel region Y, and the exhaust region Z.

Hereinafter, the film forming method on the glass substrate according to the present embodiment will be described in detail. In the present embodiment, an Al ₂ O ₃ film is formed as an alkali barrier layer on the substrate 200. Further, a TCO (Transparent Conductive Oxide) film made of SnO ₂ doped with fluorine is formed thereon as a transparent conductive film.

  Note that the alkali barrier layer is for preventing performance degradation of the solar cell due to alkali contained in the substrate 200. That is, the alkali barrier layer is a barrier layer that suppresses migration of alkali metal ions from the glass substrate. Therefore, when the substrate 200 is made of a material that does not contain much alkali, the alkali barrier layer need not be formed.

  First, the annealing point and strain point of the glass constituting the substrate 200 are measured by a beam bending method. Specifically, glass cut and ground into a predetermined shape is measured by a beam bending method (ASTM-C598) using a beam bending measuring apparatus (manufactured by Tokyo Kogyo Co., Ltd.). The slow cooling point of the glass is determined from the deflection rate under cooling. The strain point of glass is calculated.

The slow cooling point of the glass in the glass substrate according to the present embodiment is about 543 ° C. to 548 ° C., and the strain point of the glass is about 498 ° C. to 503 ° C. The annealing point of the glass is a temperature at which the internal strain of the glass is substantially removed in 15 minutes, and corresponds to the upper limit temperature in the annealing region, and the viscosity corresponds to 10 ¹³ dPa · s. The strain point of glass is a temperature at which viscous flow of glass cannot practically occur, corresponds to a lower limit temperature in a slow cooling region, and has a viscosity corresponding to 10 ^14.5 dPa · s.

As a first film formation step, an aqueous solution containing 0.15 mol / L of Al (acac) ₃ that is an oxide precursor and 20 vol% of CH ₃ COOH is sprayed onto the substrate 200 in the film formation chamber 100a. The first heating temperature in the film forming chamber 100a is set to be 300 ° C. or higher and lower than the strain point of glass. In the present embodiment, the first heating temperature is set to 350 ° C. or higher and lower than 480 ° C. More preferably, the 1st heating temperature shall be 420 degreeC or more and less than 480 degreeC. An Al ₂ O ₃ film is formed on the substrate 200 by the first film forming process.

As the second film formation step, the film formation chamber 100b contains 0.9M of SnCl ₄ · 5H ₂ O, 0.3M of NH ₄ F, 30vol% of HCl, and 2.5vol% of methanol. An aqueous solution is sprayed onto the substrate 200. The second heating temperature in the film forming chamber 100b is set to be higher than the first heating temperature and equal to or higher than the annealing point of the glass. In the present embodiment, the second heating temperature is set to 550 ° C. or more and 600 ° C. or less. More preferably, the second heating temperature is 550 ° C. or higher and 580 ° C. or lower.

  After the second film forming step, the glass substrate is held at a temperature equal to or higher than the annealing point of the glass as a strain removing step. In this embodiment, the temperature in the heating furnace 120 located on the downstream side of the film forming chamber 100b is maintained at 550 ° C. or more and 600 ° C. or less. When the temperature exceeds 600 ° C., the burden on the film forming apparatus 10 is increased, which is not preferable.

  The holding time is preferably 5 minutes or more and 30 minutes or less. When the holding time is shorter than 5 minutes, the internal strain of the substrate 200 due to the thermal history cannot be removed. When the holding time is longer than 30 minutes, the film formation tact time becomes long and the film formation efficiency decreases.

  In this embodiment, since the 2nd heating temperature is set so that it may become more than the annealing point of glass, the holding time of a distortion removal process can be shortened. As a result, the film formation tact time can be shortened and the film formation efficiency can be improved.

  After the strain removing step, the glass substrate is gradually cooled to room temperature as a slow cooling step. The slow cooling rate is preferably larger from the viewpoint of downsizing the film forming apparatus 10 and shortening the film forming tact time. Air cooling is preferably performed so that the temperature of the substrate 200 decreases at a rate of 5 ° C./min to 30 ° C./min. More preferably, air cooling is performed so that the temperature of the substrate 200 decreases at a rate of 10 ° C./min to 20 ° C./min. Thereby, the internal distortion of the substrate 200 can be prevented from remaining.

  FIG. 4 is a diagram showing a temperature profile of the substrate in the film forming method on the glass substrate according to the present embodiment. In FIG. 4, the vertical axis represents the substrate temperature, and the horizontal axis represents the substrate transfer position. The substrate transfer position indicates the range of the preheating unit 12, the film forming unit 13, and the slow cooling unit 14.

  As shown in FIG. 4, the substrate 200 is heated while passing through the preheating unit 12, and the temperature is lowered when passing through the spray region X in the film forming chamber 100 a of the film forming unit 13. Thereafter, the temperature of the substrate 200 whose temperature has risen is lowered again when it passes through the spray region X in the film forming chamber 100b of the film forming unit 13. Thereafter, the substrate 200 whose temperature has been further increased is cooled to room temperature while passing through the slow cooling section 14. The reason why the temperature of the substrate 200 decreases in the spray region X is that the heat of the substrate 200 is taken away by the heat of vaporization of water, which is a solvent of the sprayed aqueous solution.

  As described above, when a two-layer film is formed using the mist method, the substrate 200 has a thermal history due to repeated heating and cooling. When internal strain is accumulated in the substrate 200 due to the thermal history, the substrate 200 is cracked and warped.

  In the present embodiment, the second heating temperature is set higher than the first heating temperature to suppress the accumulation of internal strain of the substrate 200, and the substrate 200 is held at a temperature equal to or higher than the annealing point of the glass in the strain removing process. Thus, the internal strain of the substrate 200 is removed. As a result, a high-quality two-layer film can be formed on the substrate 200 while suppressing the occurrence of cracks and warpage in the substrate 200.

  Hereinafter, experimental examples in which film formation is performed by the film formation method on the glass substrate according to the present embodiment will be described.

(Experiment 1)
As Example 1, an Al ₂ O ₃ film having a thickness of 40 nm was formed at a first heating temperature of 475 ° C., and an SnO ₂ film having a thickness of 900 nm was formed at a second heating temperature of 570 ° C. After maintaining at 560 ° C. for 15 minutes, it was gradually cooled to room temperature.

As a comparative example, a TiO ₂ film having a thickness of 10 nm is formed on a glass substrate by sputtering, a SiO ₂ film having a thickness of 25 nm is formed thereon, and a SnO film having a thickness of 900 nm is further formed thereon. _Two films were formed.

The transmittance of the TCO film made of the SnO ₂ film obtained in Example 1 was 82%, the sheet resistance value was 10Ω / □, and the haze ratio was 10%. Moreover, the Na distribution of Example 1 and the comparative example was measured using the time-of-flight secondary ion mass spectrometer (TOF-SIMS (Time-of-flight secondary ion mass spectrometer)).

  FIG. 5 is a graph showing the measurement results of Example 1. FIG. 6 is a graph showing the measurement results of the comparative example. 5 and 6, the vertical axis represents the Na detection intensity, and the horizontal axis represents the depth from the film surface.

As shown in FIGS. 5 and 6, the detected intensity of Na in the TCO film of Example 1 was decreased in substantially the same manner as the detected intensity of Na in the TCO film of the comparative example. That is, the 40 nm thick Al ₂ O ₃ film formed by the mist method suppresses the migration of alkali metal ions from the glass substrate, almost the same as the 25 nm thick SiO ₂ film formed by the sputtering method. Was.

  From this experimental example, it was confirmed that a high-quality film can be formed by the film forming method on the glass substrate according to the present embodiment.

  Hereinafter, a film forming method on a glass substrate according to Embodiment 2 of the present invention will be described. The film forming method on the glass substrate according to the present embodiment is different from the film forming method on the glass substrate according to the first embodiment only in that the third film forming step is provided. Do not repeat.

(Embodiment 2)
In this embodiment, a TiO ₂ film is formed on the substrate 200 as a prism layer. An Al ₂ O ₃ film or MgO film is formed thereon as an alkali barrier layer. Furthermore, a TCO film made of SnO ₂ doped with fluorine is formed thereon as a transparent conductive film.

As the first film formation step, an aqueous solution of peroxotitanic acid that is an oxide precursor is sprayed onto the substrate 200 in the film formation chamber 100a. In the present embodiment, the first heating temperature is set to be 300 ° C. or higher and lower than 400 ° C. A TiO ₂ film is formed on the substrate 200 by the first film forming step.

As the second film formation step, an aqueous solution containing 0.15 mol / L of Al (acac) ₃ that is an oxide precursor and 20 vol% of CH ₃ COOH is sprayed onto the substrate 200 in the film formation chamber 100b. The second heating temperature in the film forming chamber 100b is set to be higher than the first heating temperature and lower than the strain point of the glass. In the present embodiment, the second heating temperature is 350 ° C. or higher and lower than 480 ° C. More preferably, the 2nd heating temperature shall be 420 degreeC or more and less than 480 degreeC. An Al ₂ O ₃ film is formed on the substrate 200 by the second film forming process.

  When an MgO film is formed as the alkali barrier layer, a magnesium chloride aqueous solution that is an oxide precursor is sprayed on the substrate 200. A 2nd heating temperature shall be 350 degreeC or more and less than 480 degreeC. More preferably, the second heating temperature is set to 430 ° C. or higher and lower than 480 ° C. An MgO film is formed on the substrate 200 by the second film forming step.

As the third film forming step, the film forming chamber 100c contains 0.9M of SnCl ₄ .5H ₂ O as an oxide precursor, 0.3M of NH ₄ F, 30 vol% of HCl, and 2.5 vol% of methanol. An aqueous solution is sprayed onto the substrate 200. The third heating temperature in the film forming chamber 100c is set to be higher than the second heating temperature and equal to or higher than the annealing point of the glass. In the present embodiment, the third heating temperature is set to 550 ° C. or more and 600 ° C. or less. More preferably, the third heating temperature is 550 ° C. or higher and 580 ° C. or lower.

  The strain removing step and the slow cooling step are performed in the same manner as the film forming method on the glass substrate according to the first embodiment. As described above, when a three-layer film is formed using the mist method, the substrate 200 has a thermal history due to repeated heating and cooling. When internal strain is accumulated in the substrate 200 due to the thermal history, the substrate 200 is cracked and warped.

  In the present embodiment, the third heating temperature is set higher than the first heating temperature and the second heating temperature to suppress accumulation of internal strain of the substrate 200, and at a temperature equal to or higher than the annealing point of the glass in the strain removing process. The substrate 200 is held and the internal strain of the substrate 200 is removed. As a result, a high-quality three-layer film can be formed on the substrate 200 while suppressing the occurrence of cracks and warpage in the substrate 200.

  Hereinafter, experimental examples in which film formation is performed by the film formation method on the glass substrate according to the present embodiment will be described.

(Experimental example 2)
As Example 2, a TiO ₂ film having a thickness of 20 nm is formed at a first heating temperature of 340 ° C., an Al ₂ O ₃ film having a thickness of 50 nm is formed at a second heating temperature of 475 ° C., and 3. An SnO ₂ film having a thickness of 900 nm was formed at a heating temperature of 570 ° C. After maintaining at 560 ° C. for 15 minutes, it was gradually cooled to room temperature.

The TiO ₂ film obtained in Example 2 shows a high refractive index, the transmittance of the TCO film made of SnO ₂ film is 81.5%, the sheet resistance value is 8.4Ω / □, and the haze ratio is 7.3%. Met.

  Moreover, the thin film solar cell was produced using the board | substrate with a TCO film produced in Example 2, and the characteristic value was measured. As a result, the output of the solar battery cell was 145.7 W, the open circuit voltage value was 62.2 V, the short circuit current value was 3.2 A, and the fill factor was 0.731%.

  From this experimental example, it was confirmed that a high-quality film can be formed by the film forming method on the glass substrate according to the present embodiment.

  In addition, this invention is applicable also when forming a film | membrane of four or more layers on a glass base material. In this case, the heating temperature at the time of film formation is set higher for each layer in order, and the heating temperature at the time of film formation at the end is set to be equal to or higher than the annealing point of the glass, thereby causing the glass substrate to crack and warp. While suppressing, a high quality film can be formed on the glass substrate.

  It should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 10 Film-forming apparatus, 11 Input part, 12 Preheating part, 13 Film-forming part, 14 Slow cooling part, 15 Taking-out part, 100, 100a, 100b, 100c, 100d Film-forming chamber, 110 Conveyor, 111 Conveyor belt, 112 Pulley , 113 drive shaft, 120 heating furnace, 130 spray nozzle, 131 cooling jacket, 132 rectifying member, 134 rectifying unit, 140 tank, 141 passage, 150 housing, 151 introduction port, 152 exhaust port, 153 exhaust space, 154 partition wall 155 opening, 158 spraying mechanism arrangement space, 159 film forming gas spraying space, 160 film forming material, 162 spraying region, 170 carrier gas, 180 exhaust gas, 181 mixing region, 200 substrate, 300 abatement device, 310 connecting pipe, X spray area, Y flow area, Z exhaust area.

Claims (8)

A first film forming step of forming a first layer film by spraying an aqueous solution containing an oxide precursor as a solute on a glass substrate at a first heating temperature of 300 ° C. or higher and lower than a strain point of glass;
A second film forming step of forming a second layer film by spraying an aqueous solution containing an oxide precursor as a solute on the glass substrate at a second heating temperature higher than the first heating temperature;
After the second film forming step, the strain removing step of holding the glass substrate at a temperature equal to or higher than the annealing point of the glass;
A film forming method on a glass substrate, comprising a slow cooling step of slowly cooling the glass substrate to room temperature after the strain removing step.   The method for forming a film on a glass substrate according to claim 1, wherein the second heating temperature is lower than a strain point of the glass.   The film-forming method to the glass base material of Claim 1 whose said 2nd heating temperature is more than the annealing point of the said glass.   The glass substrate according to any one of claims 1 to 3, wherein in the slow cooling step, the glass substrate is cooled so that the temperature of the glass substrate is decreased at a rate of 5 ° C / min to 30 ° C / min. Membrane method. The first layer film is a barrier layer that suppresses migration of alkali metal ions from the glass substrate;
The method for forming a film on a glass substrate according to claim 1, wherein the second layer film is a transparent conductive film. The first layer film is made of Al ₂ O ₃ ,
The first heating temperature is 350 ° C. or higher and lower than 480 ° C.,
The second layer film is made of SnO ₂ doped with fluorine,
The method for forming a film on a glass substrate according to claim 5, wherein the second heating temperature is 550 ° C or higher and 600 ° C or lower. A third film forming step is further provided between the second film forming step and the strain relief step;
In the third film forming step, an aqueous solution containing an oxide precursor as a solute is sprayed on the glass substrate at a third heating temperature higher than the second heating temperature to form a third layer film. ,
The first layer is a prism layer,
The second layer film is a barrier layer that suppresses migration of alkali metal ions from the glass substrate,
The film formation method on the glass substrate according to any one of claims 1 to 4, wherein the third layer film is a transparent conductive film. The first layer is made of TiO ₂ ,
The first heating temperature is 300 ° C. or higher and lower than 400 ° C.,
The second layer film is made of Al ₂ O ₃ or MgO,
The second heating temperature is 350 ° C. or higher and lower than 480 ° C.,
The third layer film is made of SnO ₂ doped with fluorine,
The method for forming a film on a glass substrate according to claim 7, wherein the third heating temperature is 550 ° C. or more and 600 ° C. or less.

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