JPH1126793A - Method for forming thin film solar battery cell pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a cell pattern without etching, by coating a fluorine based organic material in a pattern on a substrate, then depositing a vacuum thin film over the entire surface, washing the fluorine based organic material and the thin film deposited over it for removal to form a thin film pattern. SOLUTION: A fluorine based organic material 22a is applied in pattern on a substate 21. A metal thin film 23 is selectively grown on the entire surface of the substrate 21 to form a thin film, then submerged in a highly fluoro organic solvent to remove the fluorine based organic material 22a through ultrasonic wave washing. After the washing, only a part which is directly deposited on the substrate 21, among metal layers deposited on the entire surface of a substate, remains in pattern to form an electrode pattern. After washing the substate 21, a fluorine based organic material 22b is applied in a pattern on a part other than the electrode pattern where no amorphous silicon layer is formed, to form a 3-layer amorphous silicon layer 24 on such part as the electrode pattern and the substrate are exposed, thus, a cell pattern is formed without etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a patterning process for a thin-film solar cell. With the spread of solar cells, demands for cost reduction of solar cells are increasing. For this reason, it is important to reduce the production cost of cell patterning, which is one of the thin film solar cell production processes.
As a method of patterning the thin-film solar cell, there are methods such as laser patterning and chemical etching, all of which have high production costs. On the other hand, the present invention utilizes the selective removal or growth of the thin film, which is advantageous in reducing the production cost.

[0002]

2. Description of the Related Art Conventionally, a silicon semiconductor has been mainly used as a semiconductor material constituting a solar cell. But,
Many of the silicon semiconductors that are put into practical use are single crystals, and it is difficult to increase the area. Further, since it is a single crystal, it is expensive, the production cost is high, and the power generation cost is relatively high. On the other hand, a thin-film solar cell using amorphous silicon has attracted attention as a solar cell that has a large absorption coefficient in the visible region and can reduce power generation costs.
As the most practical configuration, for example, after forming a first electrode on a substrate, an n-layer, an i-layer, a p-layer, or a p-layer, i-layer
After forming the photovoltaic power generation layer in the order of the layer and the n-layer, a configuration is provided in which the second electrode is provided. As a substrate for these solar cells, a conductive metal material or an insulating substrate such as glass or a plastic film can be used.

FIG. 1 is a cross-sectional view showing a conventional thin film solar cell pattern manufacturing process. First, FIG.
As shown in (A), a substrate 11 such as glass or a plastic film is prepared. Next, a metal thin film to be the metal electrode layer 12 is formed by vapor deposition, sputtering, or the like to form a first electrode on the base material (FIG. 1B). The metal material may be any conductive material, such as aluminum, copper,
Chromium, silver, etc. are used. In order to pattern the metal thin film into an electrode pattern shape, a photosensitive resist material is applied on the metal thin film, photomask exposure and development are performed (FIG. 1C), and a resist film 13 is formed. Next, the metal thin film is etched through the resist film (FIG. 1D). As the etching, chemical etching using ferric chloride or the like is usually employed, but patterning using a laser can also be employed. When the resist is removed, a metal electrode pattern is formed on the base material (FIG. 1E). Usually, a series of steps from application of the resist material to exposure, development, etching, and resist peeling is referred to as “patterning”.

Next, the amorphous silicon layer 14 is formed on the metal electrode in the order of p-type, i-type, n-type or n-type, i-type, p-type.
Three layers are laminated in the order of the mold, and a photosensitive resist material is applied again to pattern the amorphous silicon layer (FIG. 1F). After a transparent conductive film 15 serving as an upper electrode is formed on the silicon layer, patterning is performed again to form a transparent electrode pattern (FIG. 1G). Finally, a passivation film 16 is formed to complete a thin-film solar cell pattern (FIG. 1 (H)).

[0005]

As described above, in the conventional method of manufacturing a thin-film solar cell by chemical etching, it is necessary to repeat "patterning", thereby increasing the manufacturing cost of the solar cell. This is the same in the case of laser patterning and the like. Accordingly, the present invention has been studied to reduce the cost of the process by selectively removing the thin film formed on the substrate or selectively depositing the thin film, thereby omitting etching after the thin film is formed. It was done.

[0006]

Means for Solving the Problems The first aspect of the present invention to solve the above-mentioned problems is that a fluorine-based organic material is applied in a pattern on a base material, and then a vacuum thin film is deposited on the entire surface. A method for forming a thin-film solar cell pattern, characterized in that a thin film pattern is formed by removing a material and a thin film deposited thereon by washing. With this forming method, thin-film solar cell patterns can be mass-produced at low cost.

[0007] The second aspect of the present invention to solve the above problems is as follows.
By applying a fluorine-based organic material in a pattern on a substrate, depositing a metal thin film over the entire surface, removing the fluorine-based organic material and the thin film deposited thereon by washing,
A method of forming a thin-film solar cell pattern, wherein an electrode pattern is formed by a metal thin film. With this forming method, thin-film solar cell patterns can be mass-produced at low cost.

[0008] The third aspect of the present invention to solve the above problems is as follows.
Is to apply a fluorine-based organic material in a pattern on a substrate on which a first electrode pattern of a metal thin film is formed, and then selectively deposit an amorphous silicon layer and remove the fluorine-based organic material by washing. Forming a pattern of an amorphous silicon layer. With this forming method, thin-film solar cell patterns can be mass-produced at low cost.

A fourth aspect of the present invention for solving the above-mentioned problems is as follows.
After applying a fluorine-based organic material in a pattern on the substrate on which the electromotive force layer of amorphous silicon was formed,
Forming an electrode pattern using a transparent conductive film by depositing a transparent conductive film over the entire surface and removing the fluorine-based organic material and the transparent conductive film deposited thereon by washing, thereby forming a thin-film solar cell pattern. In the law.
With this forming method, thin-film solar cell patterns can be mass-produced at low cost.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Pattern formation can be carried out by applying a fluorine-based organic solvent having a low vapor pressure and high heat resistance, such as foblin oil, onto a substrate in a vacuum by a printing method or the like. Note that the pattern formation can be performed in the air, but is preferably performed in a vacuum in order to avoid adverse effects such as moisture. Foblin Oil is owned by Oudimont (US:
AUSIMONT) is a chemical belonging to the perfluoropolyether developed by AUSIMONT. It is a chemically stable and inert perfluorinated oil, that is, a liquid fluororesin. Originally, it is a chemical used for lubricating oil, sealant and the like. FIG. 5 shows the chemical structure of fobulin oil. FIG. 5A shows a type having a side chain, which is synthesized from propylene hexafluoride (CF ₂ ＣＦCF—CF ₃ ) and oxygen. FIG. 5B shows a linear type, which is synthesized with tetrafluoroethylene (CF ₂ = CF ₂ ) and oxygen.

After forming a pattern with a fluorine-based organic material, a vacuum thin film is deposited on the pattern using a CVD method, a sputtering method, an evaporation method, or the like. Here, the vacuum thin film refers to various thin films such as a metal thin film, an amorphous silicon layer, and a transparent conductive film formed under reduced pressure as described above.
By doing so, a fluorine-based organic material is used as a mask (that is, a mask provided below the pattern forming material).
A thin film is deposited on the substrate and the fluorine-based organic material. Thereafter, the applied fluorine-based organic material and the thin film deposited thereon are selectively removed by dissolving or wiping with a highly fluorinated organic solvent. Alternatively, in the case of a CVD method or the like, since a vacuum thin film is not formed on a fluorine-based organic material, it is possible to selectively form a vacuum thin film on a portion other than the fluorine-based organic material. By these methods, a thin film pattern can be formed on a substrate, and a solar cell pattern can be formed without using a conventional chemical etching method. Such a fluorine-based organic material is not limited to foblin oil, but may be a fluorine-based material capable of forming a stable thin film on a substrate, for example, "KRYTOX" manufactured by DuPont.
1525 "or the like can also be used.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a cross-sectional view illustrating a method for forming a thin-film solar cell pattern according to the present invention. First, as shown in FIG. 2A, a fluorine-based organic material 22a is applied in a pattern on a substrate 21 such as glass or plastic by a printing method such as letterpress printing, flat plate printing, or screen printing. Here, a rubber letterpress printing method is suitably adopted for letterpress printing, and a flat sheet printing is performed by applying a fluorine-based organic material by a roller or the like using a punched pattern of a metal material or the like in a pattern. be able to. Screen printing is a printing method using a mesh screen and is well known to those skilled in the art. In the case of flat plate printing or screen printing, a printing method in which a magnetic plate material or a screen plate made of a ferromagnetic material is used and an electromagnet is used to attract the printing plate from below the printing table can be used, and accurate pattern printing can be performed. it can. Since the fluorine-based organic material does not form a film by drying even after coating and is in a liquid state, the film thickness is such that the coating film does not flow and the film thickness is such that coating unevenness does not occur, specifically, about 1 μm to 100 μm. It must be formed to a thickness. Therefore, it is preferable to maintain the flat surface as much as possible after coating to prevent the flow of the coating film.

Thereafter, a thin metal layer 23 serving as a first electrode is formed on the entire surface of the substrate 21 by selective growth by vapor deposition, CVD or sputtering (FIG. 2).
(B)). Next, the fluorine-based organic material is removed by means of ultrasonic cleaning performed by immersing the base material in a highly fluorinated organic solvent, dissolution by application of an organic solvent, wiping, or the like. At this time, cracks are formed in the thin film caused by vibrations caused by ultrasonic waves or pressures due to wiping, whereby the organic solvent enters below the thin film from the cracks and removes the fluorine-based organic material. As the highly fluorinated organic solvent, a low molecular weight fluorinated organic solvent can be used. After the cleaning, of the thin metal layer deposited on the entire surface of the substrate, only the portion directly deposited on the substrate remains in a pattern to form an electrode pattern (FIG. 2C). Note that fobulin oil as a fluorinated organic solvent dissolves in a highly fluorinated organic solvent such as Freon 113, perfluorooctane, or a low molecular weight product of fobulin oil ("Galden" manufactured by Oujimont Co., Ltd.), or in a fluorinated oil. However, it is hardly compatible with other water, organic solvents and fats and oils.

After the substrate is cleaned, a fluorine organic material 22b is again applied in a pattern by a printing method to portions other than the electrode pattern, where the amorphous silicon layer is not formed. Three layers (n-type layer, i-type layer, p-type
An amorphous silicon layer 24 (a mold layer) is sequentially laminated by a CVD method or the like (FIG. 2D). Since the three amorphous silicon layers may have substantially the same shape, they can be patterned by a single application of a fluorine-based organic solvent. In the case of the CVD method, selective growth is performed without forming an amorphous silicon layer on the fluorine-based organic solvent.

Although various methods are known for forming an amorphous silicon layer, a method often used is silane gas (S
iH ₄ ) is introduced into a vacuum furnace, an electric field is applied, and plasma discharge is performed to form an amorphous silicon thin film on a substrate. At this time, when no impurity is added to the silane gas, the i-type layer is added, and when diborane (B ₂ H ₆ ) is added as an impurity, the p-type layer becomes phosphine (PH ₃ ).
Is added, an n-type layer can be formed. That is, the junction of the nip layer can be formed by switching the gas. Thus, the nip type can be formed in one reaction layer only by switching the gas, but it can also be formed continuously in a line where each layer is separated in a reaction chamber. In this case, there is an effect that the residual impurities hardly have an adverse effect.

Similarly to the above, the fluorine-based organic material is removed by means of ultrasonic cleaning performed by dipping the substrate in a highly fluorinated organic solvent, dissolution by application, wiping, or the like. Thus, the amorphous silicon layer deposited on portions other than the fluorine-based organic material remains in a pattern to form the amorphous silicon layer 24 (FIG. 2E).

Subsequently, in order to form a second electrode pattern using a transparent conductive film, a fluorine-based organic material 22c is again applied in a pattern by a printing method to portions where no electrode pattern is to be formed. The portion to which the fluorine-based organic material is applied forms an insulating portion between the second electrode patterns. After forming a transparent conductive film on the entire surface of the amorphous silicon layer, the exposed portion of the base material, and the portion coated with the fluorine-based organic material (FIG. 2 (F)), ultrasonic waves immersed in a highly fluorinated organic solvent The fluorinated organic solvent is removed by means of washing or dissolving by coating, wiping or the like. In this manner, a second electrode pattern made of a transparent conductive film is formed on the substrate (FIG. 2G). Materials used for the transparent conductive film include In ₂ O ₃ , SnO ₂ , and In ₂ O ₂ -Sn.
There are O ₂ (ITO) and TiO ₂ , which can be formed by sputtering, electron beam evaporation, resistance heating evaporation, ion plating or the like.

Finally, a thin film solar cell pattern is completed by forming a passivation film by a vacuum film forming method by CVD or the like (FIG. 2 (H)). As the passivation film material, Si ₃ N ₄ , SiO ₂ or the like is preferably used, but a coating film of a polymer resin such as a fluororesin paint or a fluoride polymer having excellent weather resistance may be used.

As the substrate 11 of the thin-film solar cell, various materials can be used in addition to glass. For example, a resin film of polyimide, polyester, polyethylene terephthalate, epoxy, polyacrylate, polyarylate, or the like may be used. Alternatively, a conductive material may be used as the first electrode. In this case, stainless steel, aluminum, copper, titanium,
Galvanized steel sheets, carbon sheets and the like can be used.

In the above-mentioned processes, all the processes are performed by a pattern forming method of applying a fluorine-based organic solvent. However, other pattern forming methods can be used together. For example, the first electrode pattern and the patterning of the amorphous silicon layer are performed by the pattern forming method of the present invention using a fluorine-based organic solvent, and the second electrode pattern is formed by a sputtering method or a vapor deposition method using a mask. And so on. In particular, in the case of the vapor deposition method, the film formation pressure is lower than in the case of the CVD method, so that it is easy to use them together.

FIG. 3 is a sectional view showing a thin-film solar cell pattern according to the forming method of the present invention. The thin-film solar cell according to the formation method of the present invention does not change in structure or performance at all from the conventional pattern formation method by chemical etching. The illustrated one is a p-i-n type in which two unit cell patterns are connected in series and receive sunlight (arrows) from the transparent conductive film side. Can be obtained. A large current can be obtained by connecting the unit cell patterns in parallel. Also, by changing the order of forming the amorphous silicon layer, a nip solar cell can be obtained. Although the current obtained by such a solar cell is DC, it can be converted by an inverter into a household AC power supply.

FIG. 4 is a diagram showing an amorphous silicon layer. This portion becomes a photovoltaic layer, and an n-type amorphous silicon layer, an i-type amorphous silicon layer, and a p-type amorphous silicon layer are stacked from the substrate side.
Sunlight penetrates the transparent conductive film and absorbs photons, forming a pair of electrons and holes. However, electrons move to n-type and holes move to p-type due to the electric field existing inside the silicon substrate.
A current flows from the n-type to the p-type. This current is taken out and used.

[0023]

An embodiment of the present invention will be described below with reference to FIG. <Formation of First Electrode Pattern> A clean transparent glass substrate (Corning's “# 1737”) having a thickness of 1.1 mm and a size of 10 cm □ was prepared, and foblin oil having an average molecular weight of 7250 (“foblinr1” manufactured by Ausimont) was used.
800 ") 22a was applied in a pattern to the non-formation region of the first electrode by a rubber relief printing method (FIG. 2A). In addition, the kinematic viscosity at 20 ° C. of “foblinyr1800” was 1,850 cts, and the coating film thickness after printing was 10 μm.

The substrate 21 after the formation of the foblin oil coating film was introduced into a vapor deposition tank while maintaining the flat surface,
Was formed by a heating evaporation method using as an evaporation source (FIG. 2).
(B)). In addition, the vapor deposition conditions are as follows. (Evaporation conditions) Evaporation material: Cr (purity: 99.99%) Film formation pressure: 5 × 10 ⁻⁶ Torr Film thickness: 300 nm Film formation temperature: 350 ° C.

The base material 21 after the vapor deposition is immersed in a fobulin remover (“Garden” manufactured by Ausimont) and washed with an ultrasonic cleaner (output: 100 W, 39 KHz, 3 minutes), so that the base material is placed on the base material. Applied foblin oil 2
2a and the metal electrode layer 23 made of Cr deposited thereon were dissolved and removed, leaving only the Cr layer directly deposited on the base glass to form the first electrode pattern (FIG. 2).
(C)).

<Formation of Amorphous Silicon Layer> Foblin oil (“foblinr18” manufactured by Audimont, Inc.)
00 ”) was applied to the non-formation region of the amorphous silicon layer by the rubber relief printing method under the same conditions as in the case of forming the first electrode. The coating was performed by a printing method under the same conditions as described above.

Subsequently, the substrate was introduced into a vacuum reactor, and an amorphous silicon layer was formed by a CVD method (FIG. 2D). In this step, first, after forming an n-type amorphous silicon layer [a-Si: H (n) layer], a non-doped i-type amorphous silicon layer [a
-Si: H (i) layer], and finally, a p-type amorphous silicon layer [a-Si: H (p) layer]. The respective film forming conditions are as follows. (A-Si: H (n layer)) Film formation pressure: 500 mTorr RF input power: 50 W Introduced gas: SiH ₄ / phosphine / H ₂ (40 /
(40/80 sccm) Substrate temperature: 300 ° C. Film thickness: 50 nm Film formation time: 5 minutes (a-Si: H (i layer)) Film formation pressure: 500 mTorr RF input power: 50 W Introduced gas: SiH ₄ / H ₂ ( (40/80 sccm) Substrate temperature: 300 ° C. Film thickness: 300 nm Film formation time: 35 minutes (a-Si: H (p layer)) Film formation pressure: 500 mTorr RF input power: 50 W Introduced gas: SiH ₄ / diborane / H ₂ (40/20
/ 40sccm) Substrate temperature: 250 ° C Film thickness: 30 nm Film formation time: 3 minutes

The base material 21 after film formation is immersed in a fobulin remover (“Garden” manufactured by Ausimont) and washed with an ultrasonic cleaner (output: 100 W, 39 KHz, 3 minutes), so that the base material Oil 2 applied to
2b was dissolved and removed, and only the amorphous silicon layer selectively grown and formed on the base glass and the Cr layer remained to form an amorphous silicon layer serving as an electromotive force layer of the solar cell (FIG. 2). (E)).

<Formation of Transparent Electrode Pattern> Foblin oil (“foblinr180” manufactured by Ausimont)
0 ") was applied to the transparent electrode pattern non-formation region under the same conditions as in the first electrode formation. The coating was performed by a rubber letterpress printing method under the same conditions as described above. In the case of this embodiment,
Foblin oil will be applied to provide an insulating band at the separation zone of a single cell.

The amorphous silicon layer 24, the foblin oil-coated portion 22c and the exposed portion of the base material are covered with ITO.
Was formed by a reactive sputtering method under the following conditions (FIG. 2F). (Deposition conditions) Target: In ₂ O ₃ -SnO ₂ sintered target (SnO ₂ : 10 wt%) Deposition pressure: 5 mTorr Film thickness: 40 nm DC power: 2.5 kW Ar / O ₂ partial pressure: 100/4 sccm Film temperature: 200 ° C

The substrate after film formation is immersed in a fobulin remover (“Garden” manufactured by Ausimont) and washed with an ultrasonic cleaner (output: 100 W, 39 KHz, 3 minutes), so that the substrate is placed on the substrate. The applied fobulin oil 22c and the transparent conductive film layer formed thereon are dissolved and removed, and only the transparent conductive film layer formed on the base glass and the amorphous silicon layer remains to form the upper electrode. (Figure 2
(G)). Note that since the transparent conductive film 25 and the first electrode 23 are connected at a portion indicated by “=” in FIG. 2G, a single cell is formed as a continuous cell connected in series. Become.

<Formation of Passivation Film> Finally, a SiO ₂ film was formed on the passivation film 26 by a vacuum film forming method by CVD to complete a thin-film solar cell (FIG. 2).
(H)). The film forming conditions are as follows. (Passivation film deposition conditions) Film deposition pressure: 30 mTorr RF input power: 50 W Introduced gas: tetraethoxysilane (TEOS) Substrate temperature: 150 ° C. Film thickness: 1000 ° Film deposition time: 3 minutes

AM-1 was added to the thin film solar cell prepared above.
(Standard light source that reproduces the solar radiation spectrum on the equator)
Irradiation, the initial solar cell conversion efficiency was 7
%Met.

[0034]

As described above, according to the method for forming a thin-film solar cell pattern of the present invention, the thin-film solar cell pattern can be formed by a technique of selective growth or selective removal of a thin film which does not require a chemical etching or laser patterning process. Cell patterns can be easily formed, and capital investment, production costs,
The yield is improved, which can contribute to a reduction in the cost of the solar cell.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a thin-film solar cell pattern manufacturing process according to a conventional method.

FIG. 2 is a cross-sectional view illustrating a method of forming a thin-film solar cell pattern according to the present invention.

FIG. 3 is a cross-sectional view showing a thin-film solar cell pattern according to the formation method of the present invention.

FIG. 4 is a diagram showing an amorphous silicon layer.

FIG. 5 is a view showing a chemical structure of fobulin oil.

[Explanation of symbols]

 11, 21 Base material 12, 23 Metal electrode layer 13 Resist film 14, 24 Amorphous silicon layer 15, 25 Transparent conductive film 16, 26 Passivation film 22a, 22b, 22c Fluorine-based organic material

Claims (6)

[Claims] 1. A thin film pattern is formed by applying a fluorine-based organic material in a pattern on a substrate, depositing a vacuum thin film on the entire surface, and removing the fluorine-based organic material and the thin film deposited thereon by washing. Forming a thin film solar cell pattern. 2. A method in which a fluorine-based organic material is applied in a pattern on a substrate, a metal thin film is deposited on the entire surface, and the fluorine-based organic material and the thin film deposited thereon are removed by washing, whereby a metal thin film is formed. A method for forming a thin-film solar cell pattern, comprising forming an electrode pattern. 3. A fluorine-based organic material is applied in a pattern on a substrate on which a first electrode pattern of a metal thin film is formed, and then an amorphous silicon layer is selectively deposited,
A method for forming a thin-film solar cell pattern, wherein a pattern of an amorphous silicon layer is formed by removing a fluorine-based organic material by washing. 4. After a fluorine-based organic material is applied in a pattern on a substrate on which an electromotive force layer of amorphous silicon is formed, a transparent conductive film is deposited on the entire surface, and the fluorine-based organic material and the fluorine-containing organic material are deposited thereon. A method for forming a thin-film solar cell pattern, comprising forming an electrode pattern using a transparent conductive film by removing the transparent conductive film by washing. 5. The method for forming a thin-film solar cell pattern according to claim 1, wherein the fluorinated organic material is a side-chain or straight-chain perfluoropolyether. 6. The method for forming a thin-film solar cell pattern according to claim 1, wherein the cleaning is performed with a low molecular weight highly fluorinated organic solvent.