JP3326344B2 - Solar cell manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for manufacturing a see-through type solar cell having a plurality of light transmitting portions.

[0002]

2. Description of the Related Art Among solar cells capable of directly converting light energy into electricity, a solar cell using an amorphous semiconductor film typified by amorphous silicon has a low manufacturing cost and is easy to manufacture. It is expected to be a low-cost power solar cell because of its advantages such as a large area.

As an example of application of such an amorphous solar cell to a window glass or a sunroof of an automobile, there is a see-through type solar cell (for example, Japanese Utility Model Application Laid-Open No. 63-167758).
No.)

FIG. 7 shows the structure of this see-through type solar cell.
This will be described with reference to the structural perspective view shown in FIG.

[0005] In the figure, reference numeral 1 denotes a light-transmitting substrate made of an insulating material such as glass or quartz.
₂ , a light-transmitting electrode 2 made of a light-transmitting conductive material such as ITO,
It is made of an amorphous semiconductor and has a pin in the direction perpendicular to the film surface.
A photoelectric conversion layer 3 having a junction and a back electrode 4 made of a metal such as Ag or Al are sequentially laminated.

[0006] Further, the above-mentioned translucent electrodes 2 ..., photoelectric conversion layer 3
, And a plurality of photovoltaic elements SC are formed from the laminated body of the back electrodes 4, and adjacent photovoltaic elements SC are formed.
Are electrically connected in series by extending the back electrode 4 of one photovoltaic element SC to the translucent electrode 2 of the other photovoltaic element SC.

In addition, a plurality of light-transmitting portions H are provided by removing the stacked body of the photoelectric conversion layers 3 and the back electrodes 4 in the thickness direction.

In the solar cell having such a structure, a part of the light incident from the direction of arrow L in the figure is partially converted into the photoelectric conversion layers 3.
Contributes to the generation of photovoltaic power, while the light incident on the translucent portions H is transmitted behind through the translucent electrodes 2, so that it has power generation capability and also has translucency. Therefore, it can be applied to window glasses and sunroofs of automobiles.

A manufacturing process of such a see-through type solar cell will be described with reference to a sectional structural view of each process shown in FIG. In this figure, the same parts as those in FIG. 7 are denoted by the same reference numerals.

First, in the process shown in FIG.
The surface of a light-transmitting substrate 1 having an insulating property such as glass or quartz is coated with SnO ₂ , IT by thermal CVD or sputtering.
A light-transmitting conductive film such as O is formed, and a part thereof is removed in a groove shape by irradiation with a laser beam to form a plurality of strip-shaped light-transmitting electrodes 2.

Next, in the step shown in FIG.
The light-transmitting substrate 1 covers the light-transmitting electrodes 2.
A p-type amorphous silicon carbide film, an intrinsic amorphous silicon film, and an n-type amorphous silicon film are sequentially stacked thereon by using a plasma CVD method. Then, a predetermined portion of the stacked body of the amorphous semiconductor films is removed in a groove shape by irradiation with a laser beam to form a plurality of photoelectric conversion layers 3.

Next, in the step shown in FIG. 1C, the light-transmitting substrate 1
A metal film 4 'of g, Al or the like is formed, and a photoresist is applied on the metal film 4', and a resist pattern R is formed through exposure and development steps.

In the step shown in FIG. 1D, a plurality of back electrodes 4 are formed by removing the exposed portions of the metal film 4 'exposed from the resist pattern R by wet etching. Together with the translucent part H
Are removed from the portion corresponding to...

In this step, the transparent electrodes 2...
A plurality of photovoltaic elements SC composed of a laminate of the photoelectric conversion layers 3 and the back electrodes 4 are electrically connected to each other in series.

Finally, in the step shown in FIG. 1E, the portion of the photoelectric conversion layer 3 corresponding to the light transmitting portions H is removed by reactive ion etching using the resist pattern R as a mask. By removing the resist pattern R, the see-through type solar cell shown in FIG. 7 is manufactured.

[0016]

However, the above-mentioned method requires the steps of coating, exposing, developing, etching and the like of a photoresist, so that the process becomes complicated and the production takes a long time. .

In addition, since the size of the light transmitting portion is at most about several hundred μm in diameter, there is a problem that high-precision processing is difficult in the above-described process using a resist.

Further, in order to solve this problem, it is conceivable to process the light transmitting portion by irradiating a laser beam.
However, in the case of a see-through type solar cell, for example, 10
Since it is necessary to form about 10,000 light-transmitting parts in an area of a cm square, the method of repeatedly irradiating a spot-shaped laser beam at different positions also requires a long processing time. there were.

[0019]

According to the present invention, in order to solve the above-mentioned problems, a light-transmitting electrode, a photoelectric conversion layer, and a back electrode are laminated on a surface of a light-transmitting substrate. A method of manufacturing a solar cell including a plurality of light-transmitting portions in which a photoelectric conversion layer is removed in a film thickness direction, wherein the back electrode or a reactive gas atmosphere selected according to a material of the photoelectric conversion layer is provided. Applying high frequency power to a plurality of projecting electrodes having a small diameter to generate a point-like plasma near the apexes of the plurality of projecting electrodes; and applying the plasma to the surface of the transparent substrate. By reacting the reactive radicals generated in the plasma with the back electrode or the photoelectric conversion layer on the surface, the back electrode or the photoelectric conversion layer of the portion exposed to the plasma is exposed to the protrusions. Almost the same shape as the cross-sectional shape of the electrode Was removed, it is characterized by comprising a step of forming the light transmitting portion.

Further, the method is characterized in that the step of removing the back electrode and the step of removing the photoelectric conversion layer are performed continuously by switching the reactive gas.

Further, the present invention is characterized in that the back electrode or the photoelectric conversion layer is removed in the thickness direction by relatively bringing the light transmitting substrate and the protruding electrode closer to each other.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, referring to FIG. 1, a point-like plasma used in the manufacturing method of the present invention will be described.

FIG. 1 is a schematic diagram of a reactor for generating a point-shaped plasma. A chamber 10 evacuated by an exhaust system (not shown) has a circular cross section of about 1 cm in length and about 100 μm in diameter. A plurality of protruding electrodes 11 having a high frequency power source 13
Is provided.

Numeral 12 denotes a workpiece arranged to face the apex of the protruding electrodes 11... 14 denotes a gas introduction system for introducing a reactive gas into the chamber 10.

In the apparatus having such a structure, the chamber 10
A reactive gas is introduced into the inside, and the protruding electrodes 11 are kept at a pressure of 0.1 to 10 atm.
When a high frequency power of W is applied, the electric field is changed to the protruding electrodes 11.
Is concentrated in the vicinity of the vertex, and the plasma is localized in this portion, and a point-shaped plasma 15 having a radius of about 150 μm is generated. When the workpiece 12 is exposed to the plasma 15, reactive radicals generated in the plasma react with constituent materials of the workpiece 12, and a portion of the workpiece 12 exposed to the plasma 15 is exposed. , Projecting electrode 11
Are removed in a circular shape reflecting the sectional shape of.

When the pressure is higher than 10 atm, a point-shaped plasma is required to generate a point-shaped plasma.
Since it is necessary to increase the high-frequency power to be applied to 1,... On the other hand, if the pressure is less than 0.1 atm, the localization of the plasma is not sufficiently performed, and the processing accuracy deteriorates. Therefore, the pressure range is 0.
A range of 1 to 10 atm is preferable, and a range of 1 to 3 atm is more preferable.

The higher the frequency of the applied high frequency power, the smaller the amplitude of the electrons and ions in the plasma and the smaller the number of electrons and ions reaching the sample.
Although it is possible to reduce lattice damage and thermal damage of the sample due to collision of electrons and ions, it is technically difficult at present to supply high-frequency power having a frequency of 3 GHz or more. On the other hand, if the frequency is less than 10 MHz, the processing accuracy is lowered due to the spread of plasma in addition to the increase in lattice damage and thermal damage of the sample due to the collision of electrons and ions. Therefore, the frequency of the applied high-frequency power is 10 MHz.
z to 3 GHz is preferred.

The type of the reactive gas introduced into the chamber 10 may be appropriately selected according to the type of the sample to be processed. For example, metals such as Ag and Al, and SnO ₂ , ITO
For metal oxides such as Cl ₂ , BCl ₃ and CCl ₄
And the like are preferable. For a semiconductor film mainly composed of silicon, an F-based halogen gas such as SF ₆ or CF ₄ is preferable. Thus, by appropriately selecting the reactive gas according to the material of the film to be processed, it is possible to perform selective processing without damaging the base.

These reactive gases are usually He, Ne,
It is used after being diluted with an inert gas such as Ar. In the above-mentioned condition ranges such as the reaction pressure and the frequency of the high frequency, when the dilution ratio of the reaction gas is less than 0.1%, the concentration of the reactive radical becomes too low, so that the processing efficiency deteriorates. It becomes difficult to generate and maintain plasma. Therefore, the dilution ratio is preferably in the range of 0.1 to 30%, more preferably in the range of 0.1 to 10%.

In addition, in the present invention, the reactive gas is
By introducing the protruding electrodes 11 in the longitudinal direction as shown by arrows in FIG. 1, effective utilization of the reactive gas is achieved.

At this time, when the flow rate of the reactive gas is sonic, for example, 0 ° C. and 1 atm, 970 m / sec in He and Ne
When the temperature exceeds 435 m / sec in Ar and 319 m / sec in Ar, the state of the generated plasma tends to become unstable. Therefore, the flow rate of the reactive gas is set in the range of 0 to 200 m / sec.

Next, an embodiment of a method for manufacturing a solar cell according to the present invention will be described with reference to cross-sectional views of an element structure for each process shown in FIGS. In the figure, the same parts as those in FIG. 7 are denoted by the same reference numerals.

First, in a step shown in FIG. 2, a light-transmitting electrode 2 of SnO ₂ having a thickness of 4000 ° is formed on an insulating light-transmitting substrate 1 of glass by a thermal CVD method or a sputtering method. Then, a predetermined portion is removed in a groove shape by irradiating a laser beam to form a plurality of translucent electrodes 2.

Next, in the step shown in FIG. 3, a plasma CV is applied on the transparent substrate 1 so as to cover the transparent electrodes 2.
A D-type amorphous silicon carbide film having a thickness of about 100 ° using a D method, an intrinsic amorphous silicon film having a thickness of about 4000 °,
And an n-type amorphous silicon film having a thickness of about 200 ° was sequentially laminated.

The above-mentioned p-type amorphous silicon carbide
Film, intrinsic amorphous silicon film and n-type amorphous silicon film
In formation, SiH was used as a source gas._Four, CH_Four
And B _TwoH₆Mixed gas of SiH_FourGas, SiH_FourAnd PH
_ThreeAre used respectively.

Then, a predetermined portion of the stacked body of the amorphous semiconductor film is removed in a groove shape by irradiating a laser beam to form a plurality of photoelectric conversion layers 3.

Next, in the step shown in FIG. 4, on the translucent substrate 1 covering the plurality of photoelectric conversion layers 3.
An Al film having a thickness of about 2 μm is formed by a sputtering method or a vapor deposition method, and a predetermined portion thereof is removed in a groove shape by irradiating a laser beam to form a plurality of back electrodes 4.

By the above steps, the translucent electrodes 2...
The photoelectric conversion elements SC including the photoelectric conversion layers 3 and the back electrodes 4 are electrically connected to each other in series.

Further, in the step shown in FIG. 5, the light transmitting substrate 1 on which the light transmitting electrodes 2,..., The photoelectric conversion layers 3,. Install at the position of the workpiece.

Here, as the protruding electrodes 11, an electrode having a length of about 10 mm and a diameter of about 300 μm and having a substantially circular cross section was arranged in a matrix at intervals of about 1 mm. Then, a Cl ₂ gas diluted to about 5% with He is introduced as a reactive gas into the chamber, and a high-frequency power of a frequency of 150 MHz is applied to each of the protruding electrodes 11 while maintaining the pressure at 1 atm. By applying a power of about 20 W, a point-like plasma having a diameter of about 400 μm was generated near the apex of the protruding electrodes 11.

In this state, the surface of the light-transmitting substrate 1 is brought close to the protruding electrodes 11 by lifting means (not shown in FIG. 1), and the back electrodes 4 formed on the surface of the substrate 1 are point-shaped. , The chlorine-based reactive radicals generated in the plasma react with Al constituting the back electrodes 4. The exposed portions of the back electrodes 4. A plurality of circular portions were removed corresponding to the cross-sectional shape of.

Then, the back electrodes 4 are completely removed by further bringing the translucent substrate 1 closer to the protruding electrodes 11. The required time at this time was about 3 seconds.

At this time, if the back electrodes 4 are over-etched, the photoelectric conversion layers 3 are exposed to chlorine-based reactive radicals, and the amorphous silicon-based semiconductor forming the layers 3 is etched. There is no particular problem.

Subsequently, in the step shown in FIG. 6, the application of the high-frequency power to the protruding electrodes 11 is stopped once, the generation of plasma is stopped, and then the reactive gas is diluted to 1% with He. Switch to ₆ gases and again projecting electrodes 11 ...
To generate point-like plasma near the vertices of the protruding electrodes 11. At this time, the pressure is about 1 atm, and each of the one protruding electrodes 11 is about 1 atm.
High-frequency power with a frequency of 150 MHz was applied at a power of 0 W.

In this state, the translucent substrate 1 is brought closer to the protruding electrodes 11 by the elevating means again, and the photoelectric conversion layers 3 formed on the translucent substrate 1 are generated near the apexes of the protruding electrodes 11. To the point plasma.

In such a step, the fluorine-based reactive radicals generated in the plasma react with the amorphous silicon or amorphous silicon carbide constituting the photoelectric conversion layers 3 and are exposed to the plasma. Photoelectric conversion layer 3
Are removed in a substantially circular shape corresponding to the cross-sectional shape of the protruding electrodes 11.

Further, by bringing the light-transmitting substrate 1 closer to the protruding electrodes 11, the photoelectric conversion layers 3 are completely removed, and a plurality of the transparent electrodes 3 and the photoelectric conversion layers 3 are removed. Are formed. The required time at this time was about 1 second.

At this time, if the photoelectric conversion layers 3
Etching occurs and is transparent to fluorine-based reactive radicals
Even if the electrodes 2 are exposed, the S
nO _TwoReacts with fluorine-based reactive radicals
There is no adverse effect on the translucent electrodes 2.
No.

As described above in detail, according to the manufacturing method of the present invention, a plurality of light-transmitting portions H can be collectively processed by using a plurality of projecting electrodes 11. Thus, the manufacturing time can be greatly reduced.

Further, since the removal of the back electrodes 4 and the photoelectric conversion layers 3 is performed only by switching the reactive gas, the positional relationship between the protruding electrodes 11 and the light-transmitting substrate 1 in the planar direction changes. Therefore, the back electrodes 4 and the photoelectric conversion layers 3 can be processed at the same position with good controllability.

Further, since the production method of the present invention utilizes a chemical reaction between a reactive radical and a workpiece, it is possible to selectively process the workpiece by selecting an appropriate reactive radical. It does not adversely affect the underlying layer of the workpiece.

In addition, according to the present invention, by controlling processing conditions such as the size or pressure of the protruding electrode, the applied high-frequency power or the flow rate of the reactive gas, the protruding electrode can be formed near the apex of the protruding electrode. The size of the plasma to be applied can be controlled, and therefore, precise processing is possible.

In the above-described embodiment, the back electrode 4 or the photoelectric conversion layer 3 is removed by bringing the transparent substrate 1 closer to the protruding electrodes 11. The protruding electrodes 11 may be brought closer to the translucent substrate 1 without limitation, and the protruding electrodes 11 and the translucent substrate 1 may be made relatively closer.

Table 1 shows the output characteristics of the see-through type solar cell manufactured by using the method of the present invention and provided with 10,000 light-transmitting parts having a size of about 10 cm × 10 cm and a diameter of about 0.4 mm, and the light-transmitting parts. Indicates the processing time required to form.
Also, for comparison, a case where the semiconductor device is manufactured using a resist as Conventional Example 1 and a case where the semiconductor device is manufactured using laser light as Comparative Example 2 are also shown.

[0055]

[Table 1]

As shown in Table 1, according to the manufacturing method of the present invention, the processing of about 10,000 light-transmitting parts can be reduced to about six minutes, which is about half or less of the conventional one, and the output characteristics are high. It was found that a value was obtained.

According to the manufacturing method of the present invention, the shape of the processed portion is substantially the same as the cross-sectional shape of the protruding electrodes 11, so that, for example, if the cross-sectional shape of the protruding electrodes 11 is hexagonal, Correspondingly, the light transmitting portions H having a substantially hexagonal shape can be obtained.

[0058]

According to the manufacturing method of the present invention, a plurality of translucent portions in a see-through type solar cell are formed collectively by using a plurality of projecting electrodes 11.
The manufacturing process can be significantly reduced.

Further, since selective processing can be performed by selecting an appropriate reactive radical, there is no adverse effect on portions other than the processed portion, and the photoelectric conversion characteristics may be degraded. Absent.

In addition, when the removal processing is performed on the back electrode and the photoelectric conversion layer, the relative positional relationship between the substrate and the protruding electrodes on the plane is not changed, so that the removal processing is performed at the same position with good controllability. It can be performed.

Further, by controlling processing conditions such as the size or pressure of the protruding electrode, the applied high frequency power or the flow rate of the reactive gas, the size of the plasma generated near the apex of the protruding electrode is controlled. It can be controlled, so that precise machining is possible.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a processing apparatus used in a manufacturing method of the present invention.

FIG. 2 is an element structure diagram for each process for explaining a manufacturing method according to an embodiment of the present invention.

FIG. 3 is an element structure diagram for each process for explaining a manufacturing method according to the embodiment of the present invention.

FIG. 4 is an element structure diagram for each step for explaining a manufacturing method according to the embodiment of the present invention.

FIG. 5 is an element structure diagram for each process for explaining a manufacturing method according to the embodiment of the present invention.

FIG. 6 is an element structure diagram for each process for describing a manufacturing method according to the embodiment of the present invention.

FIG. 7 is a structural perspective view of a see-through type solar cell.

FIG. 8 is a sectional structural view for each step for explaining a conventional manufacturing step of a see-through type solar cell.

[Reference Signs] 1 ... Substrate, 2 ... Transparent electrode film, 3 ... Photoelectric conversion layer, 4 ... Back electrode, H ... Transparent portion 11 ... Protruding electrode, 15 ... Point-shaped plasma

Claims (3)

(57) [Claims] 1. A plurality of light-transmitting portions each having a light-transmitting electrode, a photoelectric conversion layer, and a back electrode laminated on a surface of a light-transmitting substrate, and the back electrode and the photoelectric conversion layer being removed in a film thickness direction. A method for manufacturing a solar cell comprising a plurality of, in a reactive gas atmosphere selected according to the material of the back electrode or the photoelectric conversion layer, a plurality of, high-frequency power to the projecting electrode having a small diameter, Applying and generating a point-shaped plasma near the apexes of the plurality of projecting electrodes; and exposing the surface of the light-transmitting substrate to the plasma.
The reactive radicals generated in the plasma are reacted with the back electrode or the photoelectric conversion layer on the surface, and the back electrode or the photoelectric conversion layer of the portion exposed to the plasma is cross-sectionally shaped by the protruding electrode. And forming the light-transmitting portion by removing the light-transmitting portion into substantially the same shape. 2. The solar cell according to claim 1, wherein the step of removing the back electrode and the step of removing the photoelectric conversion layer are performed continuously by switching the reactive gas. Manufacturing method. 3. The method according to claim 1, wherein the back electrode or the photoelectric conversion layer is removed in a thickness direction by relatively bringing the light-transmitting substrate and the protruding electrode closer to each other.
A method for manufacturing the solar cell according to the above.