JP2007231361A - Method for depositing transparent electrode film and method for producing solar battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a transparent electrode film by which the transparent electrode film simultaneously satisfying high visible light transmittance, low resistivity, and high haze can be deposited. <P>SOLUTION: The method for producing the transparent electrode film comprises : (a) a process for depositing a first transparent electroconductive film on a substrate by diluting a first raw material gas containing SnCl<SB>4</SB>and H<SB>2</SB>O in a first O/Sn ratio at a first dilution rate by an inert gas and supplying the diluted first raw material gas; (b) a process for depositing a second transparent electroconductive film on the first transparent electroconductive film by diluting a second raw material gas containing SnCl<SB>4</SB>and H<SB>2</SB>O in a second O/Sn ratio at a second dilution rate by an inert gas and supplying the diluted gas; and (c) a process for depositing a third transparent electroconductive film on the second transparent electroconductive film by diluting a third raw material gas containing SnCl<SB>4</SB>and H<SB>2</SB>O in a third O/Sn ratio at a third dilution rate by an inert gas and supplying the diluted gas. The first O/Sn ratio is larger than either of the second and third O/Sn ratios. The first dilution rate is larger than either of the second and the third dilution rates. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transparent electrode film, and more particularly to a transparent electrode film used for a solar cell.

The SnO ₂ film as the transparent electrode film is formed on the substrate by the following thermal CVD reaction at an atmospheric temperature of about 500 ° C., for example.
SnCl ₄ + 2H ₂ O → SnO ₂ + 4HCl
At this time, in order to ensure the light transmission and conductivity of the SnO ₂ film, an F-containing gas (eg, HF gas) is mixed in the source gas, and the film is formed while doping F.
An alkali barrier film may be provided between the transparent electrode film and the substrate. In particular, the alkali barrier film prevents an alkali component (such as Na) contained in the glass substrate from thermally diffusing into the transparent conductive film during film formation and over time to the transparent conductive film after film formation.
The SiO ₂ film as the alkali barrier film is formed on the substrate by the following thermal CVD reaction at an atmospheric temperature of about 500 ° C., for example.
SiH ₄ + O ₂ → SiO ₂ + 2H ₂

The performance required for the transparent electrode film used in the solar cell includes (1) high visible light transmittance, (2) low resistivity, and (3) high haze (= diffused light amount / transmitted light amount). In order to achieve these, it is desirable that SnO ₂ crystal grains in the transparent electrode film grow densely in a columnar shape. However, it is very difficult to select film forming conditions that simultaneously satisfy the performances of (1), (2), and (3). This is because there are the following difficulties in controlling the growth of SnO ₂ crystal grains. For example, if a crystal begins to grow with a dense distribution of initial nuclei on the substrate, each crystal grain inhibits each other's growth, so that none of the crystal grains can grow well. As a result, the haze is lowered. On the other hand, when the crystal starts to grow in a rough state, the resistivity increases due to disorder of the growth direction of each crystal grain and the generation of gaps between crystal grains, resulting in non-uniform haze. Performance decreases. Thus, in order to select film forming conditions that simultaneously satisfy the performances of (1), (2), and (3), it is necessary to find appropriate conditions among the conflicting conditions.

  As a related technique, Japanese Patent Application Laid-Open No. 2001-36107 discloses a photoelectric conversion device substrate and a photoelectric conversion device using the same. The substrate for a photoelectric conversion device includes a glass plate and a conductive film mainly composed of tin oxide formed on the glass plate, and a chlorine concentration in the conductive film is 0.11% by weight or less, The fluorine concentration in the conductive film is not less than the chlorine concentration. This is intended to improve the light transmittance by optimizing the F concentration doped in the transparent conductive film to suppress the Cl concentration taken into the film.

  In addition, WO2003 / 065386 discloses a method for forming a transparent conductive film, the transparent conductive film, a glass substrate including the transparent conductive film, and a photoelectric conversion device using the glass substrate. This method of forming a transparent conductive film is a method of forming a transparent conductive film containing tin oxide as a main component on a glass ribbon by a CVD method. A transparent conductive film is formed at a film forming rate of 3000 to 7000 nm / min using a raw material gas containing 0.5 to 2.0 mol% of an organic tin compound. This is intended to make the crystal grains uniform by suppressing the growth of huge crystal grains using the organic tin compound source gas.

Japanese Patent Application Laid-Open No. 2001-59175 discloses a tin oxide film, a manufacturing method thereof, and a tin oxide film manufacturing apparatus. In this method of manufacturing a tin oxide film, a tin oxide film is formed on a glass substrate that moves in one direction by reacting tin tetrachloride with water by an atmospheric pressure CVD method. The atmosphere when forming a tin oxide film by discharging a gas containing tin tetrachloride and water onto the glass substrate is such that the upstream side in the moving direction of the glass substrate has a higher water concentration than the downstream side. It is characterized by. This is intended to increase the H ₂ O / SnCl ₄ ratio in the initial stage of film formation and to increase the affinity and stabilize the crystal growth by increasing the amount of water.

JP 2001-36107 A WO2003 / 065386 JP 2001-59175 A

  Accordingly, an object of the present invention is to provide a method for forming a transparent electrode film capable of forming a transparent electrode film that simultaneously satisfies high visible light transmittance, low resistivity, and high haze.

  Another object of the present invention is to provide a solar cell manufacturing method capable of manufacturing a highly efficient solar cell using a transparent electrode film that simultaneously satisfies high visible light transmittance, low resistivity, and high haze. It is in.

  Hereinafter, means for solving the problem will be described using the numbers and symbols used in the best mode for carrying out the invention. These numbers and symbols are added with parentheses to clarify the correspondence between the description of the claims and the best mode for carrying out the invention. However, these numbers and symbols should not be used for interpreting the technical scope of the invention described in the claims.

In the method for producing a transparent electrode film of the present invention, (a) a first source gas containing SnCl ₄ and H ₂ O at an O / Sn first ratio is used, and the ratio of the first source gas to the inert gas is first. Diluting and supplying at a dilution rate to form a first transparent conductive film (22) above the substrate (20); (b) a second layer containing SnCl ₄ and H ₂ O at a _second O / Sn ratio. A step of forming a second transparent conductive film (23) on the first transparent conductive film (22) by supplying two source gases after the ratio of the second source gas to the inert gas is diluted at the second dilution rate; (C) supplying a third source gas containing SnCl ₄ and H ₂ O at an O / Sn third ratio diluted with a third dilution ratio of the third source gas to an inert gas; Forming a third transparent conductive film (24) on the two transparent conductive films (23). The O / Sn first ratio is greater than the O / Sn second ratio and the O / Sn third ratio. The first dilution rate is greater than the second dilution rate and the third dilution rate. Here, when N ₂ is used as the inert gas, the dilution rate becomes the N ₂ / Sn ratio.
In the present invention, by setting the O / Sn first ratio to be larger than the O / Sn second and third ratio, the surface of the alkali barrier film (SiO ₂ ) that is the base for forming the first transparent conductive film (22) is formed. H ₂ O can be initially adsorbed on the entire surface. As a result, SnCl ₄ reacts with H ₂ O uniformly and densely, so that initial nuclei for SnO ₂ crystal grain growth can be uniformly and densely formed. Further, by making the first dilution ratio larger than the second and third dilution ratios, when SnCl ₄ and H ₂ O react to form SnO ₂ initial nuclei, the crystals after the initial nucleation are formed. Since the growth is suppressed, the initial nuclei are formed on the entire surface, so that the initial nuclei can be formed more uniformly and densely. As a result, crystal grains can be grown uniformly and densely in a columnar shape, and a transparent electrode film that simultaneously satisfies high visible light transmittance, low resistivity, and high haze can be formed.

In the transparent electrode film forming method, the O / Sn second ratio is equal to the O / Sn third ratio. The second dilution rate is preferably equal to or greater than the third dilution rate.
According to the present invention, the film forming speed of the third transparent conductive film can be increased, and the productivity can be improved.

In the method for forming a transparent electrode film, the second dilution rate is preferably 1.0 to 2.0 times the third dilution rate.
According to the present invention, the film quality distribution can be made more uniform while increasing the film forming speed of the third transparent conductive film.

In the method for producing a transparent electrode film, the first O / Sn ratio is 40 or more and 100 or less. The first dilution rate is preferably 500 times or more and 1000 times or less.
According to the present invention, initial nuclei for crystal grain growth of the SnO ₂ film can be appropriately and uniformly formed densely.

In the method for forming a transparent electrode film, the O / Sn second ratio and the O / Sn third ratio are 10 or more and 70 or less. The second dilution ratio and the third dilution ratio are preferably 100 times or more and 700 times or less.
According to the present invention, initial nuclei for crystal grain growth of the SnO ₂ film can be appropriately and uniformly formed densely.

In the method for forming a transparent electrode film, in the step (a), the first source gas contains HF at an F / Sn first ratio. In the step (b), the second source gas contains HF in the F / Sn second ratio. In the step (c), the third source gas contains HF in an F / Sn third ratio. The F / Sn first ratio is preferably smaller than the F / Sn second ratio and the F / Sn third ratio.
According to the present invention, by reducing the supply of HF at the time of initial nucleus formation, F that hinders the growth of the initial nucleus of the SnO ₂ film can be reduced, and the formation of the initial nucleus can be promoted.

In the above method for forming a transparent electrode film, the F / Sn first ratio is preferably (1/10) or more and (1/2) or less of the F / Sn second ratio and the F / Sn third ratio. .
According to the present invention, the resistance of the transparent electrode film can be lowered while promoting the growth of the initial nucleus of the SnO ₂ film.

)
In the method for forming a transparent electrode film, the F / Sn third ratio is preferably equal to or smaller than the F / Sn second ratio.
According to the present invention, when a solar cell is formed on the transparent electrode film, the efficiency can be further improved.

In the method of forming a transparent electrode film, (d) a fourth source gas containing SiH ₄ and O ₂ at an O / Si first ratio is supplied, and the substrate (20) and the first transparent conductive film (22) are supplied. And the step of forming an alkali barrier film (21) between the two. The O / Si first ratio is 40 or more and 200 or less. The thickness of the alkali barrier film (21) is preferably 20 nm or more and 60 nm or less, and more preferably 30 nm or more and 50 nm or less.
In the present invention, by sufficiently increasing the O / Si ratio, O ₂ can be initially adsorbed on the entire surface of the substrate. Thereby, SiH ₄ reacts uniformly and densely with O ₂ , and the initial nucleus of SiO ₂ crystal grain growth becomes uniform and dense. Since the SiO ₂ film becomes uniform and dense, the film thickness of SiO ₂ is 60 nm or less and a film with less disorder of the crystal structure can be obtained. Since the SiO ₂ crystal grains are uniform and dense, and the surface properties thereof are good, the first transparent conductive film (22) that generates initial nuclei starting from it grows the initial nuclei more uniformly and densely. I can do it.

According to the method for forming a transparent electrode film of the present invention, (a) a first source gas containing SnCl ₄ , H ₂ O, and HF at an F / Sn first ratio is supplied to Forming a first transparent conductive film (22); and (b) supplying a second source gas containing SnCl ₄ , H ₂ O, and HF at an F / Sn second ratio, ) Forming a second transparent conductive film (23) thereon; (c) supplying a third source gas containing SnCl ₄ , H ₂ O, and HF at an F / Sn third ratio to provide a second transparent Forming a third transparent conductive film (24) on the conductive film (23). The F / Sn first ratio is smaller than the F / Sn second ratio and the F / Sn third ratio.

  In the method for forming a transparent electrode film, the first F / Sn ratio is not less than (1/10) and not more than (1/2) of the F / Sn second ratio and the F / Sn third ratio.

  In the method for forming a transparent electrode film, the F / Sn third ratio is equal to or smaller than the F / Sn second ratio.

The method for producing a transparent electrode film of the present invention comprises: (a) supplying a fourth source gas containing SiH ₄ and O ₂ at an O / Si first ratio, and forming an alkali barrier film (21) on a substrate (20). And (b) supplying a first source gas containing SnCl ₄ and H ₂ O diluted with an inert gas and supplying the first transparent conductive film (22) on the alkali barrier film (21). And (c) supplying a second source gas containing SnCl ₄ and H ₂ O diluted with an inert gas and supplying the second transparent conductive film (23) on the first transparent conductive film (22). And (d) supplying a third raw material gas containing SnCl ₄ and H ₂ O diluted with an inert gas and supplying the third transparent conductive film (24) on the second transparent conductive film (23). ). The O / Si first ratio is 40 or more and 200 or less. The thickness of the alkali barrier film (21) is 20 nm or more and 60 nm or less, more preferably 30 nm or more and 50 nm or less.

  The manufacturing method of the solar cell of this invention is the manufacturing method of the transparent electrode film as described in any one of (a) Claims 1 thru | or 13, A transparent electrode film (21 + 25) is formed on a translucent board | substrate (20). A step of forming; (b) a step of forming a photoelectric conversion layer (26) for converting light into electricity on the transparent electrode film (21 + 25); and (c) a back electrode film on the photoelectric conversion layer (26). (27) forming a step.

  According to the present invention, it is possible to form a transparent electrode film that simultaneously satisfies high visible light transmittance, low resistivity (or low sheet resistance), and high haze. Moreover, it becomes possible to manufacture a highly efficient solar cell using a transparent electrode film that simultaneously satisfies high visible light transmittance, low resistivity, and high haze.

  Hereinafter, embodiments of a method for producing a transparent electrode film and a method for producing a solar cell according to the present invention will be described with reference to the accompanying drawings.

(First embodiment)
First, a first embodiment of the transparent electrode film forming method of the present invention will be described. FIG. 1 is a schematic diagram showing a configuration of a film forming apparatus in a first embodiment of a transparent electrode film forming method of the present invention. The film forming apparatus 30 forms the transparent electrode film of the present invention on a translucent substrate 20 (example: 1.4 m × 1.1 m soda glass substrate) by a thermal CVD method. The transparent electrode film includes an alkali barrier film and a transparent conductive film. The film forming apparatus 30 includes a first chamber 1, a second chamber 2, a third chamber 3, a fourth chamber 4, a first gas supply unit 5, a second gas supply unit 6, a first gas seal unit 7, and a second gas. A sealing unit 8, a first heating unit 9, a second heating unit 10, a conveyor 11, a water cooling unit 12, a film forming chamber 18, and a control unit 19 are provided.

  The film forming chamber 18 is a rectangular parallelepiped chamber in which an alkali barrier film and a transparent conductive film are formed on the substrate 20. The film forming chamber 18 has an inlet 18a at one end in the longitudinal direction, an outlet 18b at the other end, and a region A to a region H that are provided between the inlet 18a and the outlet 18b and perform various processes. A first gas seal portion 7, a first heating portion 9, a first chamber 1, a second chamber 2, a third chamber 3, a fourth chamber 4, water cooling are provided above the regions A to H inside the film forming chamber 18. The part 12 and the second gas seal part 8 are provided in this order from the inlet 18a. Further, the second heating unit 10 is provided below the regions D to F. In addition, the conveyor 11 is provided from the inlet 18a toward the outlet 18b.

  The conveyor 11 is provided so as to penetrate the film forming chamber 18 from the inlet 18a toward the outlet 18b. After exiting from the outlet 18b, it passes under the film forming chamber 18 and returns to the inlet 18a. In the conveyor 11, the substrate 20 is placed on the conveyor 11, enters the film forming chamber 18 from the inlet 18a, is subjected to predetermined processing in each of the areas A to H, and is sent out from the outlet 18b.

  The first gas seal portion 7 is provided in the upper part of the region A in the vicinity of the inlet 18 a in the film forming chamber 18. By blowing an inert gas (for example, nitrogen gas) into the region A, the atmosphere in the film forming chamber 18 is prevented from flowing out from the inlet 18a. The first heating unit 9 is provided above and below the region B adjacent to the region A inside the film forming chamber 18. The substrate 20 passing through the region B is heated to a predetermined temperature.

The first chamber 1 is provided in an upper part of a region C adjacent to the region B in the film forming chamber 18. An alkali barrier film is formed on the substrate 20 that passes through the region C. Here, by sending SiH ₄ gas and O ₂ gas onto the substrate 20 passing through the region C, a SiO ₂ film as an alkali barrier film is formed on the substrate 20 by a thermal CVD method.

The first gas supply unit 5 supplies a source gas to the first chamber 1. In the present embodiment, the SiH ₄ gas having the mass flow meter 13a and the mass flow meter 13b, the flow rate of which is controlled by the mass flow meter 13a, and the O ₂ gas of which the flow rate is controlled by the mass flow meter 13b are respectively supplied to the first chamber 1. Supply.

The second chamber 2 is provided above the region D adjacent to the region C in the film forming chamber 18. A first transparent conductive film (hereinafter referred to as a first transparent conductive film) is formed on the substrate 20 passing through the region D. Here, SnCl ₄ gas, H ₂ O gas, and HF gas are diluted with N ₂ gas and sent to the substrate 20 that passes through the region D, so that the first transparent conductive film is formed on the substrate 20 by thermal CVD. A SnO ₂ film doped with F is formed. Excess gas is discharged from the exhaust gas line.

The third chamber 3 is provided above the region E adjacent to the region D in the film forming chamber 18. A second transparent conductive film (hereinafter referred to as a second transparent conductive film) is formed on the substrate 20 passing through the region E. Here, SnCl ₄ gas, H ₂ O gas, and HF gas are diluted with N ₂ gas and sent onto the substrate 20 that passes through the region E, so that the second transparent conductive film is formed on the substrate 20 by thermal CVD. A SnO ₂ film doped with F is formed. Excess gas is discharged from the exhaust gas line.

The fourth chamber 4 is provided above the region F adjacent to the region E inside the film forming chamber 18. A third transparent conductive film (hereinafter referred to as a third transparent conductive film) is formed on the substrate 20 passing through the region F. Here, SnCl ₄ gas, H ₂ O gas, and HF gas are diluted with N ₂ gas and sent out on the substrate 20 passing through the region F, thereby forming a third transparent conductive film on the substrate 20 by thermal CVD. A SnO ₂ film doped with F is formed. Excess gas is discharged from the exhaust gas line.

The second gas supply unit 6 supplies the source gas to each of the second chamber 4 to the fourth chamber 4. It has mass flow meters 14a-14c, mass flow meters 15a-15c, mass flow meters 16a-16c, and mass flow meters 17a-17c. The HF gas whose flow rate is controlled by the mass flow meter 14c, the H ₂ O gas whose mass flow meter 15c is controlled, the SnCl ₄ gas whose flow rate is controlled by the mass flow meter 16c, and the N ₂ gas whose flow rate is controlled by the mass flow meter 17c are respectively listed. 2 Supply to chamber 2 Similarly, HF gas whose flow rate is controlled by the mass flow meter 14b, H ₂ O gas whose mass flow meter 15b is controlled, SnCl ₄ gas whose flow rate is controlled by the mass flow meter 16b, and N ₂ gas whose flow rate is controlled by the mass flow meter 17b. Are supplied to the third chamber 3, respectively. The HF gas whose flow rate is controlled by the mass flow meter 14a, the H ₂ O gas which is controlled by the mass flow meter 15a, the SnCl ₄ gas whose flow rate is controlled by the mass flow meter 16a, and the N ₂ gas whose flow rate is controlled by the mass flow meter 17a, respectively. Supply to 4 chambers 4.

  The second heating unit 10 is provided below the region D to the region F inside the film forming chamber 18. The substrate 20 passing through the regions D to F is heated and maintained at a predetermined temperature in each region. The water cooling unit 12 is provided in the upper part of the region G adjacent to the region F in the film forming chamber 18. The temperature of the substrate 20 passing through the region G is lowered to a predetermined temperature or lower. The second gas seal portion 8 is provided in the upper portion of the region H (adjacent to the region G) in the vicinity of the outlet 18b in the film forming chamber 18. By blowing an inert gas (for example, nitrogen gas) to the region H, the atmosphere in the film forming chamber 18 is prevented from flowing out from the outlet 18b.

  The control unit 19 includes a first gas seal unit 7, a first heating unit 9, a first chamber 1, a first gas supply unit 5, a second chamber 2, a third chamber 3, a fourth chamber 4, and a second gas supply unit. 6. Control operations of the second heating unit 10, the second gas seal unit 8, the conveyor 11, and the water cooling unit 12. In particular, the gas in each of the mass flow meters 13a and 13b of the first gas supply unit 5, the mass flow meters 14a to 14c, the mass flow meters 15a to 15c, the mass flow meters 16a to 16c, and the mass flow meters 17a to 17c in the second gas supply unit 6. Perform flow control.

Next, the film forming conditions in the first embodiment of the transparent electrode film forming method of the present invention will be described. Here, when forming a film of the transparent conductive film (SnO ₂ film), among the three chambers (second chamber to fourth chamber 4), the first transparent conductive film forming a film initially (SnO ₂ film) Then, the film is formed under film forming conditions different from the film forming conditions of the second transparent conductive film (SnO ₂ film) and the third transparent conductive film (SnO ₂ film) to be formed thereafter. That is, the film forming conditions in the second chamber 2 are different from those in the subsequent chambers (the third chamber 3 to the fourth chamber 4). However, the ratio of the flow rate of the HF gas that is the doping gas to the flow rate of the SnCl ₄ gas is the same in the second chamber 2 to the fourth chamber 4.

As the film forming conditions for the first transparent conductive film, the O / Sn ratio in the source gas (H ₂ O gas + SnCl ₄ gas + HF gas) is increased and the film forming speed is kept low. That is, the ratio of the H ₂ O gas flow rate / SnCl ₄ gas flow rate (O / Sn ratio) in the second chamber 2 is increased to 40 or more and 100 or less (preferably 50 or more and 80 or less). At the same time, the dilution rate of the source gas with N ₂ gas (N ₂ / Sn ratio) is set to 500 times or more and 1000 times or less (preferably 600 times or more and 800 times or less) to reduce the film forming speed. At this time, the flow rate of the SnCl ₄ gas flow rate is, for example, 0.1 SLM. The flow rate of the HF gas is, for example, 0.05 SLM.

By sufficiently increasing the O / Sn ratio in the second chamber 2, H ₂ O can be initially adsorbed on the entire surface of the alkali barrier film (SiO ₂ ). Thereby, SnCl ₄ reacts with H ₂ O uniformly and densely, and the initial nuclei of SnO ₂ crystal grain growth become uniform and dense. However, if the O / Sn ratio is excessively increased, H ₂ O is excessively adsorbed on the surface of the alkali barrier film (SiO ₂ ), and the crystal growth of each crystal grain is inhibited from each other. Will be uneven. Therefore, the O / Sn ratio in the second chamber 2, that is, the ratio of the H ₂ O gas flow rate / SnCl ₄ gas flow rate is in the above range.

Further, by sufficiently diluting the source gas in the second chamber 2 with N ₂ gas, SnCl ₄ reacts with H ₂ O to form SnO ₂ initial nuclei. Crystal growth is suppressed and initial nuclei are formed on the entire surface, so that the initial nuclei are more uniform and dense. However, if the source gas is diluted too much with N ₂ gas, the reaction becomes too slow and the formation of initial nuclei becomes uneven, and the initial nuclei become uneven and the film-forming speed becomes slow. As a result, the conductivity is lowered. Therefore, the dilution rate with N ₂ gas in the second chamber 2 is in the above range. The gas to be diluted may be an inert gas other than N ₂ gas (eg, Ar), but N ₂ gas is easy to use from the viewpoint of cost.

As the film forming conditions for the second transparent conductive film and the third transparent conductive film, the O / Sn ratio in the source gas is reduced and the film forming speed is set as compared with the film forming conditions for the first transparent conductive film. Keep it low. That is, the ratio of the H ₂ O gas flow rate / SnCl ₄ gas flow rate in the third chamber 3 and the fourth chamber 4 is relatively reduced to 10 or more and 70 or less (preferably 20 or more and 50 or less). At the same time, the dilution rate of the source gas with N ₂ gas is diluted to be relatively lower than that of the second chamber 2 (example: 100 times or more and 700 times or less (preferably 300 times or more and 500 times or less)). Increase. It is preferable to increase the film forming rate by a factor of 3 or more. At this time, the flow rate of the SnCl ₄ gas flow rate is, for example, 0.3 SLM. The flow rate of HF gas is, for example, 0.3 SLM.

By reducing the O / Sn ratio in the third chamber 3 and the fourth chamber 4, it is possible to prevent each crystal grain from interfering with or inhibiting each other's growth, thereby reducing haze, and reducing the film forming speed. . However, if the O / Sn ratio is too small, the film forming speed becomes too fast, crystal growth becomes non-uniform, and a film thickness distribution occurs. Therefore, the O / Sn ratio in the second chamber 2, that is, the ratio of the H ₂ O gas flow rate / SnCl ₄ gas flow rate is in the above range.

Furthermore, by reducing the dilution rate of the source gas with N ₂ gas in the third chamber 3 and the fourth chamber 4, it is possible to increase the film forming speed and improve the productivity. However, if the dilution rate with N ₂ gas is made too small, the film forming speed becomes too fast, the crystal growth becomes non-uniform, and the film thickness distribution occurs. Therefore, the dilution rate by the N ₂ gas in the third chamber 3 and the fourth chamber 4 is in the above range. The gas to be diluted may be an inert gas other than N ₂ gas (eg, Ar), but N ₂ gas is easy to use from the viewpoint of cost.

FIG. 2 is a schematic cross-sectional view of a transparent electrode film formed by the film forming method of the present invention and a conventional film forming method. (A) is the transparent electrode film formed by the conventional film forming method, and (b) is the transparent electrode film formed by the film forming method of the transparent electrode film of the present invention. However, the conventional film forming method is a method using the same O / Sn ratio and dilution rate with N ₂ gas from the second chamber 2 to the fourth chamber 4.

  Referring to (a), as the transparent electrode film, the alkali barrier film 121 formed in the first chamber 1 on the substrate 120, the first transparent conductive film 122 formed in the second chamber 2, and the third chamber. The second transparent conductive film 123 formed in 3 and the third transparent conductive film 124 formed in the fourth chamber 4 are formed. In the transparent conductive film 125 (122 + 123 + 124), the first transparent conductive film 122 as an initial nucleus of crystal grain growth is in a non-uniform and sparsely distributed state. For this reason, the second transparent conductive film 123 grown thereon inherits the state, and the growth direction is disturbed due to non-uniform distribution. Further, the third transparent conductive film 124 grown thereon inherits the state, and the growth direction is disturbed due to the non-uniform distribution. That is, since uneven and disordered crystal grain growth occurs, the transparent conductive film 125 has low visible light transmittance, high resistivity, and low haze.

On the other hand, referring to (b), as the transparent electrode film, an alkali barrier film 21 formed in the first chamber 1, a first transparent conductive film 22 formed in the second chamber 2, and a third film on the substrate 20. A second transparent conductive film 23 formed in the chamber 3 and a third transparent conductive film 24 formed in the fourth chamber 4 are formed. In the method for producing a transparent conductive film of the present invention, by increasing the O / Sn ratio in the second chamber 2, H ₂ O is initially adsorbed on the entire surface of the alkali barrier film 21 (SiO ₂ ). Then, SnCl ₄ sufficiently diluted with N ₂ gas reacts with the initially adsorbed H ₂ O and becomes an initial nucleus of SnO ₂ crystal grain growth. Therefore, in this transparent conductive film 25 (22 + 23 + 24), the first transparent conductive film 22 as the initial nucleus is in a uniformly and densely distributed state. For this reason, the second transparent conductive film 23 grown on the second conductive film 23 also inherits the state, and is in a state where the growth direction is uniform with a uniform distribution. Further, the third transparent conductive film 24 grown thereon is also inherited, and is in a state where the growth direction is uniform with a uniform distribution. That is, since uniform and columnar crystal grain growth occurs, the transparent conductive film 25 has a high visible light transmittance, a low resistivity, and a high haze.

Next, the process of the transparent electrode film forming method of the present invention using the film forming apparatus 30 will be described. FIG. 14 is a flowchart showing an embodiment of a method for forming a transparent electrode film according to the present invention.
The substrate 20 is moved from the inlet 18a into the film forming chamber 18 by the conveyor 11, and is heated to a predetermined temperature by the first heating unit 9 in the region B. Thereafter, the substrate 20 reaches the region C. The control unit 19 controls the mass flow controllers 13a and 13b so that SiH ₄ gas and O ₂ gas flow at a flow rate that satisfies the conditions described in the present embodiment. The mass flow controllers 13a and 13b supply a source gas containing SiH ₄ and O ₂ onto the substrate 20 to form the alkali barrier film 21 on the substrate (step S11).

The substrate 20 is moved by the conveyor 11 and heated to a predetermined temperature by the second heating unit 10 in the region D. The control unit 19 controls the mass flow controllers 16c, 15c, 14c, and 17c so that SnCl ₄ gas, H ₂ O gas, and HF gas N ₂ gas flow at the flow rates that satisfy the conditions described in the present embodiment. The mass flow controllers 16c, 15c, 14c, and 17c supply the first source gas containing SnCl ₄ gas, H ₂ O gas, and HF gas onto the substrate 20 while diluting with N ₂ gas. The first transparent conductive film 22 is formed (Step S12).

The substrate 20 is moved by the conveyor 11 and heated to a predetermined temperature in the region E by the second heating unit 10. The control unit 19 controls the mass flow controllers 16b, 15b, 14b, and 17b so that SnCl ₄ gas, H ₂ O gas, HF gas, and N ₂ gas flow at the flow rates that satisfy the conditions described in the present embodiment. The mass flow controllers 16b, 15b, 14b, and 17b supply the first transparent conductive film 22 to the substrate 20 while diluting the second source gas containing SnCl ₄ gas, H ₂ O gas, and HF gas with N ₂ gas. A second transparent conductive film 23 is formed thereon (step S13).

The substrate 20 is moved by the conveyor 11 and heated to a predetermined temperature by the second heating unit 10 in the region F. The control unit 19 controls the mass flow controllers 16a, 15a, 14a, and 17a so that SnCl ₄ gas, H ₂ O gas, HF gas, and N ₂ gas flow at the flow rates that satisfy the conditions described in the present embodiment. The mass flow controllers 16a, 15a, 14a, and 17a supply the second source conductive gas containing SnCl ₄ gas, H ₂ O gas, and HF gas onto the substrate 20 while diluting with N ₂ gas, and the second transparent conductive film 23 is supplied. A second transparent conductive film 24 is formed thereon (step S14).

The substrate 20 is moved by the conveyor 11 and is cooled by the water cooling unit 12 in the region G. Thereafter, the film is delivered from the film forming chamber 18 through the outlet 18b.
As described above, the transparent electrode film is formed.

FIG. 3 is a graph showing the relationship between the sheet resistance and the ratio of the H ₂ O gas flow rate / SnCl ₄ gas flow rate in the first embodiment of the transparent electrode film forming method of the present invention. The vertical axis represents the normalized sheet resistance. The horizontal axis represents the ratio of the standardized H ₂ O gas flow rate / SnCl ₄ gas flow rate including the optimum range. A range in which the ratio of the H ₂ O gas flow rate / SnCl ₄ gas flow rate in the graph (curve) is small generally corresponds to the optimum range. This figure shows the third chamber 3 and the fourth chamber 4. Ratio of H ₂ O gas flow rate / SnCl ₄ gas flow rate = O / Sn ratio can be reduced to reduce sheet resistance.

FIG. 4 is a graph showing the relationship between the haze ratio and the ratio of the H ₂ O gas flow rate / SnCl ₄ gas flow rate in the first embodiment of the transparent electrode film forming method of the present invention. The vertical axis represents the normalized haze rate. The horizontal axis represents the ratio of the standardized H ₂ O gas flow rate / SnCl ₄ gas flow rate including the optimum range. A range in which the ratio of the H ₂ O gas flow rate / SnCl ₄ gas flow rate in the graph (curve) is small generally corresponds to the optimum range. This figure shows the third chamber 3 and the fourth chamber 4. Ratio of H ₂ O gas flow rate / SnCl ₄ gas flow rate = O / Sn ratio can be reduced to increase the haze ratio.

FIG. 5 is a graph showing the relationship between the sheet resistance and the dilution rate of the source gas with N ₂ gas in the first embodiment of the transparent electrode film forming method of the present invention. The vertical axis represents the normalized sheet resistance. The horizontal axis represents the dilution rate of the source gas with the standardized N ₂ gas including the optimum range. The range with a large dilution rate in the graph (curve) generally corresponds to the optimum range. This figure shows the third chamber 3 and the fourth chamber 4. By increasing the dilution rate of the source gas with N ₂ gas, the sheet resistance can be reduced.

FIG. 6 is a graph showing the relationship between the haze ratio and the dilution rate of the source gas with N ₂ gas in the first embodiment of the method for forming a transparent electrode film of the present invention. The vertical axis represents the normalized haze rate. The horizontal axis represents the dilution rate of the source gas with the standardized N ₂ gas including the optimum range. The range with a large dilution rate in the graph (curve) generally corresponds to the optimum range. This figure shows the third chamber 3 and the fourth chamber 4. By increasing the dilution rate of the source gas with N ₂ gas, the haze rate can be increased.

As shown in FIGS. 3 to 6, for the third chamber 3 and the fourth chamber 4, by reducing the O / Sn ratio and / or increasing the dilution rate of the source gas with N ₂ gas, Resistance can be lowered and haze ratio can be increased.

By making the O / Sn ratio in the second chamber 2 in which the initial nucleus SnO ₂ is deposited and the dilution rate with N ₂ gas appropriate by the film deposition method of the present invention, the growth of the initial nucleus is made uniform and dense. Can be made. As a result, the second transparent conductive film and the third transparent conductive film grown thereon can also take over the same state and be uniform and dense. That is, good crystal grain growth can be obtained. Thereby, a transparent electrode film having a high visible light transmittance, a low resistivity, and a high haze can be obtained. By using this for the surface electrode of a solar cell, the performance (conversion efficiency) of the solar cell can be improved.

(Second Embodiment)
Next, a second embodiment of the transparent electrode film forming method of the present invention will be described. In the present embodiment, the film forming apparatus 30 is the same as that in the first embodiment (FIG. 1), but the film forming conditions are different from those in the first embodiment.

The film forming conditions in the second embodiment of the transparent electrode film forming method of the present invention will be described. In the present embodiment, the conditions for forming the first transparent conductive film (SnO ₂ film) and the second transparent conductive film (SnO ₂ film) are the same as in the case of the first embodiment. However, it differs from the case of the first embodiment in that the conditions increase in the film forming conditions of the third transparent conductive film (SnO ₂ film).

As conditions for forming the third transparent conductive film, the O / Sn ratio in the source gas (H ₂ O gas + SnCl ₄ gas + HF gas) is the same as the conditions for forming the second transparent conductive film. That is, the ratio of the H ₂ O gas flow rate / SnCl ₄ gas flow rate (O / Sn ratio) in the third chamber 3 and the fourth chamber 4 is set to the same value of 10 to 70 (preferably 20 to 50). . However, the dilution rate of the source gas with N ₂ gas is made smaller than the dilution rate with the second transparent conductive film. The film forming speed of the first transparent conductive film ≦ the film forming speed of the second transparent conductive film ≦ the film forming speed of the third transparent conductive film. Since the crystal growth of the first transparent conductive film and the second transparent conductive film grows smoothly, columnar growth is performed, so that the deposition rate of the third transparent conductive film can be further increased by further reducing the dilution rate to improve productivity. It becomes possible. The degree of reducing the dilution rate is set to (1 / 1.0) times to (1 / 2.0 times). If it is smaller than this, the effect of improving the productivity is too low, and if it is larger than this, the film forming speed becomes too fast and the film thickness distribution occurs.

  The steps of the transparent electrode film forming method of the present invention using the film forming apparatus 30 are the same as those in the first embodiment except that the film forming conditions are different.

  Also in this embodiment, a transparent electrode film having a cross-sectional structure as shown in FIG. 2B can be obtained. The same effects as those of the first embodiment can be obtained. In addition, productivity can be improved by increasing the film forming speed.

(Third embodiment)
Next, a third embodiment of the transparent electrode film forming method of the present invention will be described. In the present embodiment, the film forming apparatus 30 is the same as that in the first embodiment (FIG. 1), but the film forming conditions are different from those in the first embodiment.

The film forming conditions in the third embodiment of the transparent electrode film forming method of the present invention will be described. In the present embodiment, under the film forming conditions, the O / Sn ratio in the source gas and the dilution rate with the N ₂ gas are the same as those in the first embodiment. However, the conventional conditions which can form a transparent conductive film may be sufficient. However, the second embodiment differs from the first embodiment in that the ratio of the HF gas flow rate to the SnCl ₄ gas flow rate is different between the second chamber 2 and the third chamber 3 to the fourth chamber 4.

As the film forming conditions of the first transparent conductive film, the O / Sn ratio in the source gas (H ₂ O gas + SnCl ₄ gas + HF gas) and the dilution rate with N ₂ gas are the same as those in the first embodiment. is there. That is, the O / Sn ratio is set to 40 or more and 100 or less (preferably 50 or more and 80 or less), and the dilution rate of the source gas with N ₂ gas is set to 500 times or more and 1000 times or less (preferably 600 times or more and 800 times or less). However, the F / Sn ratio in the source gas is made relatively small. That is, the ratio of the HF gas flow rate / SnCl ₄ gas flow rate in the second chamber 2 is not less than (1/10) of the ratio of the HF gas flow rate / SnCl ₄ gas flow rate in the third chamber 3 and the fourth chamber 4 (1 / 2) Make relatively small below. This is because F in the doping gas has an effect of preventing the growth of initial nuclei of the SnO ₂ film. Therefore, the formation of initial nuclei can be promoted by reducing the flow rate of HF at the time of initial nucleation (second chamber 2) and reducing the supply of F. Thereby, subsequent crystal grain growth can be appropriately advanced. If the F / Sn ratio is greater than (1/2), the initial nucleation is adversely affected. If the F / Sn ratio is less than (1/10), the first transparent conductive film becomes too high in resistance. The flow rate of the HF gas is, for example, 0.05 SLM.

  As a film forming condition of the first transparent conductive film to the third transparent conductive film, it is preferable that the F / Sn ratio is 1.0 or less in any case. This is because if the F / Sn ratio is larger than 1.0, the transmittance of the transparent conductive film is lowered. Further, by relatively increasing the F / Sn ratio in the third chamber and the fourth chamber 4, it is possible to compensate for an increase in resistivity due to a decrease in F amount in the first transparent conductive film.

  The steps of the transparent electrode film forming method of the present invention using the film forming apparatus 30 are the same as those in the first embodiment except that the film forming conditions are different.

FIG. 7 is a graph showing the relationship between the sheet resistance and the ratio of the HF gas flow rate / SnCl ₄ gas flow rate in the first embodiment of the transparent electrode film forming method of the present invention. The vertical axis represents the normalized sheet resistance. The horizontal axis shows the ratio of the normalized HF gas flow rate / SnCl ₄ gas flow rate including the optimum range. A range in which the ratio of the HF gas flow rate / SnCl ₄ gas flow rate in the graph (curve) is large generally corresponds to the optimum range. This figure shows the third chamber 3 and the fourth chamber 4. The ratio of HF gas flow rate / SnCl ₄ gas flow rate = F / Sn ratio can be increased to reduce the sheet resistance.

FIG. 8 is a graph showing the relationship between the haze ratio and the ratio of the HF gas flow rate / SnCl ₄ gas flow rate in the first embodiment of the transparent electrode film forming method of the present invention. The vertical axis represents the normalized haze rate. The horizontal axis shows the ratio of the normalized HF gas flow rate / SnCl ₄ gas flow rate including the optimum range. A range in which the ratio of the HF gas flow rate / SnCl ₄ gas flow rate in the graph (curve) is large generally corresponds to the optimum range. This figure shows the third chamber 3 and the fourth chamber 4. Ratio of HF gas flow rate / SnCl ₄ gas flow rate = F / Sn ratio can be increased to increase the haze ratio.

  As shown in FIGS. 7-8, about 3rd chamber 3 and 4th chamber 4, sheet resistance can be made low and haze rate can be made high by enlarging F / Sn ratio.

  Also in this embodiment, a transparent electrode film having a cross-sectional structure as shown in FIG. 2B can be obtained. The same effects as those of the first embodiment can be obtained. In addition, since the formation of initial nuclei can be promoted, the initial nuclei can be grown more uniformly and densely. Thereby, the second transparent conductive film and the third transparent conductive film grown thereon can also take over the state, and can be made more uniform and dense. That is, better crystal grain growth can be obtained. Furthermore, the second transparent conductive film and the third transparent conductive film can increase the F / Sn ratio and decrease the resistivity. Thereby, a transparent electrode film having higher visible light transmittance, lower resistivity (sheet resistance), and higher haze is obtained.

(Fourth embodiment)
Next, a fourth embodiment of the transparent electrode film forming method of the present invention will be described. In the present embodiment, the film forming apparatus 30 is the same as that in the first embodiment (FIG. 1), but the film forming conditions are different from those in the first embodiment.

The film forming conditions in the fourth embodiment of the transparent electrode film forming method of the present invention will be described. In the present embodiment, under the film forming conditions, the O / Sn ratio in the source gas, the dilution rate with N ₂ gas, and the F / Sn ratio are the same as those in the third embodiment. However, the third embodiment differs from the third embodiment in that the F / Sn ratio condition increases in the film forming condition of the third transparent conductive film (SnO ₂ film).

As the film forming conditions for the third transparent conductive film, the relationship of the F / Sn ratio in the source gas (H ₂ O gas + SnCl ₄ gas + HF gas) to the F / Sn ratio in the first transparent conductive film is as follows: The film forming conditions are the same. That is, the F / Sn ratio of the third transparent conductive film is larger than the F / Sn ratio of the first transparent conductive film. However, the F / Sn ratio in the source gas is relatively equal or smaller than the F / Sn ratio in the second transparent conductive film. That is, the ratio of the HF gas flow rate / SnCl ₄ gas flow rate in the fourth chamber 4 is made equal to or smaller than the ratio of the HF gas flow rate / SnCl ₄ gas flow rate in the third chamber 3. That is, the F / Sn ratio in the first transparent conductive film <the F / Sn ratio in the third transparent conductive film ≦ the F / Sn ratio in the second transparent conductive film. Even if the F / Sn ratio of the third transparent conductive film is the same value as the F / Sn ratio of the second transparent conductive film, crystal grain growth is performed at a high speed here, so that F of the third transparent conductive film is F The same effect can be obtained as when the / Sn ratio is set small. As a result, when the power generation layer of the solar cell is formed on the transparent electrode film, the contact resistance is reduced because the conductivity of the boundary surface in contact with the power generation layer (example: a-Si (p layer)) is improved. In addition, the efficiency of the solar cell is improved.

  The steps of the transparent electrode film forming method of the present invention using the film forming apparatus 30 are the same as those in the first embodiment except that the film forming conditions are different.

  Also in this embodiment, a transparent electrode film having a cross-sectional structure as shown in FIG. 2B can be obtained. The same effects as those of the first embodiment can be obtained. In addition, when a solar cell is formed on the transparent electrode film, the visible light has a high transmittance and a high haze, so that the solar cell can effectively use incident light. Further, since the resistivity (sheet resistance) is lower and the contact resistance at the boundary surface is reduced, a large amount of current can be taken out with little loss, so that the efficiency can be further improved.

(Fifth embodiment)
Next, a fifth embodiment of the transparent electrode film forming method of the present invention will be described. In the present embodiment, the film forming apparatus 30 is the same as that in the first embodiment (FIG. 1), but the film forming conditions are different from those in the first embodiment.

The film forming conditions in the fifth embodiment of the transparent electrode film forming method of the present invention will be described. In the present embodiment, the conditions for forming the first transparent conductive film (SnO ₂ film) to the third transparent conductive film (SnO ₂ film) are the same as in the case of the first embodiment. However, the conventional conditions which can form a transparent conductive film may be sufficient. However, it differs from the case of the first embodiment in that the film forming conditions of the alkali barrier film (SiO ₂ film) are different.

The alkali barrier film has a function of preventing the alkali component (particularly Na) contained in the glass substrate from thermally diffusing into the transparent conductive film during film formation and diffusing over time into the transparent conductive film after film formation; There is a function which becomes a starting point of initial nucleus formation at the time of forming a transparent conductive film (SnO ₂ film). Here, the starting point of the initial nucleation is formed small and with high density, and the coverage of the alkali barrier film on the substrate is improved. For this purpose, the conditions for forming the alkali barrier film are as follows.

As the film forming conditions for the alkali barrier film, the O / Si ratio in the source gas (SiH ₄ gas + O ₂ gas) is increased to keep the film forming speed low. That is, the ratio of the O ₂ gas flow rate / SiH ₄ gas flow rate in the first chamber 1 is increased to 20 or more and 100 or less (preferably 40 or more and 60 or less). In this case, the O / Si ratio is 40 to 200 (preferably 80 to 120). The film thickness is 20 to 60 nm (more preferably 30 to 50 nm). At this time, the flow rate of the SiH ₄ gas flow rate is, for example, 0.03 SLM.

By sufficiently increasing the O / Si ratio in the first chamber 1, O ₂ can be initially adsorbed on the entire surface of the substrate. Thereby, SiH ₄ reacts uniformly and densely with O ₂ , and the initial nucleus of SiO ₂ crystal grain growth becomes uniform and dense. As a result, a uniform SiO ₂ film (alkali barrier film) having a high coverage can be formed. However, if the O / Sn ratio is excessively increased, SiH ₄ is diluted, resulting in a decrease in film formation speed and a decrease in productivity. On the other hand, when the SiO ₂ film thickness is 20 nm or less, the alkali component (Na) in the substrate diffuses into the film and the alkali barrier effect is lowered. When the SiO ₂ film thickness is increased to 60 nm or more and grown, the crystal grain size increases and a gap is formed between adjacent crystal grains. The uniformity of the crystal grain growth of SnO _{2 as} a film is hindered, and the performance of the transparent conductive film is lowered. Therefore, the O / Si ratio in the first chamber 1, that is, the ratio of O ₂ gas flow rate / SiH ₄ gas flow rate, and the film thickness are in the above range.

  The steps of the transparent electrode film forming method of the present invention using the film forming apparatus 30 are the same as those in the first embodiment except that the film forming conditions are different.

FIG. 9 is a graph relating to the coverage of the alkali barrier film in the fifth embodiment of the transparent electrode film forming method of the present invention. The vertical axis represents the ratio (coverage) of covering the substrate with the initial nucleus of SiO ₂ , and the horizontal axis represents the normalized SiH ₄ flow rate. It can be seen that the coverage decreases as the SiH ₄ flow rate increases. This is presumably because SiH ₄ cannot react uniformly and densely with SiO ₂ , and the initial nuclei of SiO ₂ crystal grain growth are generated unevenly and grain growth occurs.

  Also in this embodiment, a transparent electrode film having a cross-sectional structure as shown in FIG. 2B can be obtained. The same effects as those of the first embodiment can be obtained. In addition, since more starting points for the formation of the initial nuclei of the first transparent conductive film can be generated, the initial nuclei can be grown more uniformly and densely. Thereby, the second transparent conductive film and the third transparent conductive film grown thereon can also take over the state, and can be made more uniform and dense. That is, better crystal grain growth can be obtained. Thereby, a transparent electrode film having higher visible light transmittance, lower resistivity, and higher haze can be obtained.

In the first to fifth embodiments, each of SnCl ₄ gas, H ₂ O gas, HF gas, and N ₂ gas for the transparent conductive film is separately supplied to each chamber. However, the conditions in the first to fifth embodiments (O / Sn ratio, dilution ratio with N ₂ gas: N ₂ / Sn ratio, F / Sn ratio, etc.) are satisfied during film formation. In other words, it may be supplied in another form (for example, supplied from a cylinder in which at least two kinds of gases are mixed).

  The techniques described in the first to fifth embodiments can be applied to the transparent electrode film manufacturing method at the same time as long as no contradiction occurs.

  Next, a solar cell to which the transparent electrode film formed in the first to fifth embodiments of the transparent electrode film forming method of the present invention is applied, and a method for manufacturing the solar cell. explain.

  FIG. 10 is a cross-sectional view showing an example of the configuration of a solar cell using a transparent electrode film formed by the transparent electrode film forming method of the present invention. Here, the amorphous solar cell 50 will be described. However, the transparent electrode film of the present invention is not limited thereto, and can be applied to other types of solar cells (eg, microcrystalline solar cells, tandem solar cells).

  The amorphous solar cell 50 includes a substrate 20, an alkali barrier film 21 and a transparent conductive film 25 as a transparent electrode film of the present invention, a power generation layer 26, and a back electrode film 27. The battery layer 26 is an amorphous silicon battery layer and includes an amorphous p-layer film 31, an amorphous i-layer film 32, and a microcrystalline n-layer film 33. However, a buffer layer may be provided between the amorphous p layer film 31 and the amorphous i layer film 32 in order to improve the interface characteristics.

  Next, a method for manufacturing the solar cell 50 shown in FIG. 10 will be described. FIG. 11 is a flowchart showing an embodiment of a method for manufacturing a solar cell of the present invention. A soda float glass substrate (1.4 m × 1.1 m × plate thickness: 4 mm) is used as the substrate 20. It is desirable that the end face of the substrate is corner chamfered or rounded to prevent breakage.

Using the first chamber 1 in the film forming apparatus 30 of FIG. 1, a silicon oxide film (SiO ₂ film) as the alkali barrier film 21 is formed on the substrate 20 by a thermal CVD method (step S01). The alkali barrier film 21 is formed by applying the film forming method of the fifth embodiment. FIG. 12 is a table showing conditions for forming the alkali barrier film. In this figure, CH: 1 indicates the first chamber 1. The flow rate of SiH _{4 in} the first chamber 1 (CH: 1) is A (L / min.). The film forming temperature is about 500 ° C., and the film forming pressure is about atmospheric pressure. This film forming condition is the film forming condition of the film forming method of the fifth embodiment. Here, 50 (O / Si ratio is 100) is selected as the ratio of O ₂ gas flow rate / SiH ₄ gas flow rate. The film forming speed is 10 to 20 nm / min. It is. The film formation time is about 2.5 minutes. Thus, SiO ₂ film 25~50nm is formed.

Next, using the second chamber 4 to the fourth chamber 4 in the film forming apparatus 30 of FIG. 1, an F-doped tin oxide film (SnO ₂ film) is formed on the alkali barrier film 21 as a transparent conductive film 25 by a thermal CVD method. To form a film (step S02). FIG. 13 is a table showing conditions for forming the transparent conductive film. In this figure, CH: 2 represents the second chamber 2, CH: 3 represents the third chamber 3, and CH: 4 represents the fourth chamber 4. The SnCl ₄ flow rate in the second chamber 2 (CH: 2) is B (L / min.), The film forming temperature is about 500 ° C., and the film forming pressure is about atmospheric pressure. This film forming condition is a film forming condition of the film forming method of the first embodiment and the third embodiment. Here, in the second chamber 2, the third chamber 3, and the fourth chamber 4, the ratio of the H ₂ O gas flow rate / SnCl ₄ gas flow rate (O / Sn ratio) is 60, 27, and 27, respectively, and N _{2 of} the source gas. Dilution ratios with gas (N ₂ / Sn ratio) are 680 times, 133 times and 133 times, respectively, and ratios of HF gas flow rate / SnCl ₄ gas flow rate (F / Sn ratio) are 0.4 times, 0.8 times and 0.8 times is selected. The film forming rate is 20 to 50 nm / min. 50-150 nm / min. And 50 to 150 nm / min. It is. Each of the film forming times is about 2.5 minutes. Thereby, an F-doped SnO ₂ film of 300 to 900 nm is formed.

  By the steps S01 and S02, the transparent electrode film of the present invention can be formed. Thereby, a transparent electrode film having dense and uniform columnar crystal grains can be obtained. As a result, a transparent electrode film having high visible light transmittance, low resistivity (sheet resistance), and high haze can be obtained.

  Then, the board | substrate 20 is installed in an XY table. Then, the first harmonic (1064 nm) of the laser diode pumped YAG laser is irradiated to a predetermined position on the substrate 20 to process the transparent conductive film and the alkali barrier film into a predetermined strip shape (step S03). .

  Subsequently, an amorphous p-layer film 31 / amorphous i-layer film 32 / microcrystalline n-layer film 33 as the amorphous silicon-based battery layer 35 are sequentially formed by a plasma CVD apparatus at a reduced pressure atmosphere of 30 to 150 Pa and about 200 ° C. (Step S04). The amorphous p-layer film 31 is mainly made of B-doped amorphous SiC and has a thickness of 10 to 30 nm. The amorphous i-layer film 32 is mainly made of amorphous Si and has a thickness of 200 to 350 nm. The microcrystalline n-layer film 33 is mainly P-doped microcrystalline Si and has a thickness of 30 to 50 nm.

  The substrate 51 is set on an XY table. Then, the second harmonic (532 nm) of the laser diode-pumped YAG laser is irradiated to a predetermined position on the substrate 20 to process the battery layer 26 into a predetermined strip shape (step S05).

  By using a sputtering apparatus, an Ag film and a Ti film are sequentially formed as a back electrode film 27 at a reduced pressure atmosphere: 1 to 5 Pa and about 150 ° C. In the present embodiment, the back electrode film 27 is formed by laminating an Ag film: 200 to 500 nm and a Ti film: 10 to 20 nm in this order (step S06).

  The substrate 51 is set on an XY table. Then, the second harmonic (532 nm) of the laser diode-pumped YAG laser is irradiated to a predetermined position on the substrate 20 to process the back electrode film 27 into a predetermined strip shape (step S07).

  The solar cell of this invention can be manufactured according to said each process.

  Since the solar cell manufactured by the method for manufacturing a solar cell according to the present invention uses the transparent electrode film of the first to fifth embodiments, a highly efficient solar cell can be manufactured. It becomes possible.

FIG. 1 is a schematic view showing a configuration of a film forming apparatus in an embodiment of a transparent electrode film forming method of the present invention. FIG. 2 is a schematic cross-sectional view of a transparent electrode film formed by the film forming method of the present invention and a conventional film forming method. FIG. 3 is a graph showing the relationship between the sheet resistance and the ratio of the H ₂ O gas flow rate / SnCl ₄ gas flow rate in the first embodiment of the transparent electrode film forming method of the present invention. FIG. 4 is a graph showing the relationship between the haze ratio and the ratio of the H ₂ O gas flow rate / SnCl ₄ gas flow rate in the first embodiment of the transparent electrode film forming method of the present invention. FIG. 5 is a graph showing the relationship between the sheet resistance and the dilution rate of the source gas with N ₂ gas in the first embodiment of the transparent electrode film forming method of the present invention. FIG. 6 is a graph showing the relationship between the haze ratio and the dilution rate of the source gas with N ₂ gas in the first embodiment of the method for forming a transparent electrode film of the present invention. FIG. 7 is a graph showing the relationship between the sheet resistance and the ratio of the HF gas flow rate / SnCl ₄ gas flow rate in the first embodiment of the transparent electrode film forming method of the present invention. FIG. 8 is a graph showing the relationship between the haze ratio and the ratio of the HF gas flow rate / SnCl ₄ gas flow rate in the first embodiment of the transparent electrode film forming method of the present invention. FIG. 9 is a graph relating to the coverage of the alkali barrier film in the fifth embodiment of the transparent electrode film forming method of the present invention. FIG. 10 is a cross-sectional view showing an example of the configuration of a solar cell using a transparent electrode film formed by the transparent electrode film forming method of the present invention. FIG. 11 is a flowchart showing an embodiment of a method for manufacturing a solar cell of the present invention. FIG. 12 is a table showing conditions for forming the alkali barrier film. FIG. 13 is a table showing conditions for forming the transparent conductive film. FIG. 14 is a flowchart showing an embodiment of a method for forming a transparent electrode film according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st chamber 2 2nd chamber 3 3rd chamber 4 4th chamber 5 1st gas supply part 6 2nd gas supply part 7 1st gas seal part 8 2nd gas seal part 9 1st heating part 10 2nd heating part DESCRIPTION OF SYMBOLS 11 Conveyor 12 Water cooling part 13 Control part 18 Film-forming chamber 18a Inlet 18b Outlet 20, 120 Substrate 21, 121 Alkali barrier film 22, 122 First transparent conductive film 23, 123 Second transparent conductive film 24, 124 Third transparent conductive film 25, 125 Transparent conductive film 26 Power generation layer 27 Back electrode film 30 Film-forming device 31 Amorphous p-layer film 32 Amorphous i-layer film 33 Microcrystalline n-layer film 50 Solar cell

Claims (14)

(A) A first source gas containing SnCl ₄ and H ₂ O at an O / Sn first ratio is supplied by diluting at a first dilution ratio of the first source gas to an inert gas, Forming a first transparent conductive film above
(B) supplying a second source gas containing SnCl ₄ and H ₂ O at an O / Sn second ratio, diluted at a second dilution ratio of the second source gas to the inert gas, Forming a second transparent conductive film on the first transparent conductive film;
(C) A third source gas containing SnCl ₄ and H ₂ O at an O / Sn third ratio is supplied after being diluted at a third dilution ratio of the third source gas to the inert gas, Forming a third transparent conductive film on the second transparent conductive film,
The O / Sn first ratio is greater than the O / Sn second ratio and the O / Sn third ratio;
The first dilution rate is greater than the second dilution rate and the third dilution rate. A method for forming a transparent electrode film. In the film-forming method of the transparent electrode film of Claim 1,
The O / Sn second ratio is equal to the O / Sn third ratio;
The method for forming a transparent electrode film, wherein the second dilution rate is equal to or greater than the third dilution rate. In the film-forming method of the transparent electrode film of Claim 2,
The second dilution rate is 1.0 to 2.0 times the third dilution rate. A method for forming a transparent electrode film. In the film-forming method of the transparent electrode film as described in any one of Claims 1 thru | or 3,
The first O / Sn ratio is 40 or more and 100 or less,
Said 1st dilution rate is 500 times or more and 1000 times or less The film forming method of a transparent electrode film. In the film-forming method of the transparent electrode film of Claim 4,
The O / Sn second ratio and the O / Sn third ratio are 10 or more and 70 or less,
The method for forming a transparent electrode film, wherein the second dilution ratio and the third dilution ratio are 100 times or more and 700 times or less. In the film-forming method of the transparent electrode film as described in any one of Claims 1 thru | or 5,
In the step (a), the first source gas includes HF in an F / Sn first ratio,
In the step (b), the second source gas contains HF in an F / Sn second ratio,
In the step (c), the third source gas contains HF in an F / Sn third ratio,
The F / Sn first ratio is smaller than the F / Sn second ratio and the F / Sn third ratio. In the film-forming method of the transparent electrode film of Claim 6,
The F / Sn first ratio is (1/10) or more and (1/2) or less of the F / Sn second ratio and the F / Sn third ratio. In the film-forming method of the transparent electrode film of Claim 6 or 7,
The F / Sn third ratio is equal to or smaller than the F / Sn second ratio. In the film-forming method of the transparent electrode film as described in any one of Claims 1 thru | or 8,
(D) supplying a fourth source gas containing SiH ₄ and O ₂ at an O / Si first ratio, and further forming an alkali barrier film between the substrate and the first transparent conductive film. Equipped,
The O / Si first ratio is 40 or more and 200 or less,
The alkali barrier film has a film thickness of 20 nm to 60 nm. (A) supplying a first source gas containing SnCl ₄ , H ₂ O and HF at an F / Sn first ratio to form a first transparent conductive film above the substrate;
(B) supplying a second source gas containing SnCl ₄ , H ₂ O, and HF at an F / Sn second ratio to form a second transparent conductive film on the first transparent conductive film;
(C) supplying a third source gas containing SnCl ₄ , H ₂ O, and HF at an F / Sn third ratio to form a third transparent conductive film on the second transparent conductive film. And
The F / Sn first ratio is smaller than the F / Sn second ratio and the F / Sn third ratio. In the film forming method of the transparent electrode film according to claim 10,
The F / Sn first ratio is (1/10) or more and (1/2) or less of the F / Sn second ratio and the F / Sn third ratio. The method for forming a transparent electrode film according to claim 10 or 11,
The F / Sn third ratio is equal to or smaller than the F / Sn second ratio. (A) supplying a fourth source gas containing SiH ₄ and O ₂ at an O / Si first ratio to form an alkali barrier film on the substrate;
(B) diluting and supplying a first source gas containing SnCl ₄ and H ₂ O with an inert gas, and forming a first transparent conductive film on the alkali barrier film;
(C) supplying a second source gas containing SnCl ₄ and H ₂ O diluted with an inert gas and forming a second transparent conductive film on the first transparent conductive film;
(D) diluting and supplying a third source gas containing SnCl ₄ and H ₂ O with an inert gas, and forming a third transparent conductive film on the second transparent conductive film,
The O / Si first ratio is 40 or more and 200 or less,
The alkali barrier film has a film thickness of 20 nm to 60 nm. (A) In the method for producing a transparent electrode film according to any one of claims 1 to 13, a step of forming a transparent electrode film on a light-transmitting substrate;
(B) forming a photoelectric conversion layer that converts light into electricity on the transparent electrode film;
(C) forming a back electrode film on the photoelectric conversion layer. A method for producing a solar cell.

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