JPH0766438A - Manufacture of substrate for photoelectric transducer - Google Patents

Abstract

PURPOSE:To uniformly form a semiconductor film of few defects by a low temperature film forming means which film is constituted of a polymer film provided with a texture trench, by forming a polymer film layer on the surface of a master by a spin-coating method, and baking the polymer film layer. CONSTITUTION:A master 3 for a substrate is mounted on a spinner. While the master 3 is rotated, solution wherein polyimide monomer is dissolved in methyl ethyl ketone is dripped on the master 4 surface. After a polymer film layer is peeled from the master 3 for a substrate, the polymer film layer on which etch-pits of the master 3 are transferred is baked. Thus a polymer film substrate 4 is manufactured. A polymer film substrate provided with a texture trench wherein the crest part and the valley part are worked in a curved surface can be simply and surely manufactured, and the photoelectric conversion efficiency of an obtained photoelectric transducer can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a substrate for a photoelectric conversion device applied to a photoelectric conversion device such as a film-forming solar cell or an image sensor, and more particularly to a polymer film having textured grooves. The present invention relates to a method of manufacturing a substrate for a photoelectric conversion device, which can uniformly form a semiconductor film having few defects by a low temperature film forming means.

[0002]

2. Description of the Related Art As a substrate for a photoelectric conversion device of this type having a textured groove, one made of single crystal silicon in which an etch pit is formed by an etching process is conventionally known.

However, since this single crystal silicon substrate lacks mass productivity and its cost is relatively high, metal,
Substrates for photoelectric conversion devices made of inexpensive materials such as glass and polymer films have been demanded.

Based on such a request, the applicant of the present invention has mastered the single crystal silicon in which the etch pit is formed,
A substrate for a photoelectric conversion device excellent in mass productivity, light weight, flexibility, etc., in which texture grooves are formed by transferring the etch pits to a polymer film surface, and a method for manufacturing the same have already been proposed (Japanese Patent Laid-Open No. HEI-1- No. 302776).

4A and 4B show an example of a film-forming solar cell in which the polymer film substrate is incorporated. That is, this film-forming solar cell has a texture groove a1.
Polymer film substrate a on which is formed, a back surface conductive film b made of aluminum or the like provided on the surface thereof, and amorphous silicon formed on the n layer c1, i layer c2, and p layer c3. The layer c and the transparent conductive film d provided on the amorphous silicon layer c constitute the main part.

[0006]

By the way, FIG. 4 (B)
As shown in, the texture has a high degree of texture (that is, it means that the top and valley of the texture groove a1 have a square shape).
When a semiconductor film such as an amorphous silicon layer is formed on the surface of a polymer film substrate by a film forming means such as a sputtering method or a plasma CVD (chemical vapor deposition) method whose film forming conditions are relatively low, Texture groove as shown in Figure 5
The semiconductor film formed on the top and the valley of a1 is likely to have defects, and the film properties of the formed semiconductor film are not good. Therefore, in the photoelectric conversion device obtained due to this, although the texture groove a1 acts to effectively absorb light (this is called a light confinement effect), its photoelectric conversion efficiency is not so high. It had a problem that it did not rise.

When the polymer film substrate having a high degree of texture is applied, a method of applying a thermal CVD method instead of the above-mentioned low temperature film forming method such as the sputtering method or the plasma CVD method may be considered. That is, by applying this thermal CVD method and appropriately setting the film forming conditions, it is possible to improve the film characteristics of the semiconductor film formed on the top and valley of the texture groove a1. Is.

However, this thermal CVD method has a higher film forming condition than the low temperature film forming method such as the above-mentioned sputtering method or plasma CVD method, so that it is difficult to apply it to a polymer film substrate having no heat resistance. there were.

On the other hand, the surface of the single crystal silicon on which the etch pits are formed is subjected to isotropic etching, and the top and valley of the etch pits are processed into a curved surface shape to form single crystal silicon with reduced texture. A method of producing the polymer film substrate using this as a master is also considered.

However, when the surface of the single crystal silicon on which the etch pits are formed is isotropically etched, the sloped surfaces of the etch pits are uniformly etched in addition to the etching of the tops and valleys of the etch pits, and the surface is flattened. Therefore, the surface of the polymer film substrate manufactured by using this single crystal silicon as a master is also flat, and it is difficult to form textured grooves on the surface. Then, due to this, the light confinement effect is lowered, so that there is a problem that the photoelectric conversion efficiency does not increase so much as in the case where a polymer film substrate having a high texture is applied.

The present invention has been made by paying attention to such a problem, and an object thereof is to provide a semiconductor film composed of a polymer film having textured grooves and having few defects by a low temperature film forming means. It is an object of the present invention to provide a method for manufacturing a substrate for a photoelectric conversion device that allows uniform film formation.

[0012]

That is, the invention according to claim 1 is premised on a method for manufacturing a substrate for a photoelectric conversion device composed of a polymer film having a textured groove, and a single unit having an etch pit is formed. A thin film is formed on the surface of crystalline silicon by a low temperature film forming method, and the thin film and the surface of single crystal silicon are etched using an etching agent having an etching rate for crystalline silicon higher than the etching rate for the thin film, and the etching pit A master forming step of forming a master for a substrate by processing each of the top and the valley into a curved shape, and forming a polymer film layer on the surface of the master by a spin coating method, and forming the polymer film layer. After being peeled off from the master, the polymer film layer on which the etch pits of the master are transferred is baked to produce a photoelectric conversion device. The invention according to claim 2 is based on a method for manufacturing a substrate for a photoelectric conversion device formed of a polymer film having textured grooves. A thin film is formed on the surface of the single crystal silicon on which the etch pits are formed by a low temperature film forming method, and the thin film and the single crystal silicon surface are formed by using an etching agent having an etching rate for the crystalline silicon higher than the etching rate for the thin film. Master processing step of etching and processing the top and valley of the etch pits into curved shapes to create a master for the substrate, and forming a thin film made of a material having a hardness higher than that of crystalline silicon on the surface of the master And, after attaching a holding material to this thin film via an adhesive, the master is lapped and etched by And a stamper making process for making a stamper composed of a thin film on which the master etch pits have been transferred and a holding material, and the etch pits provided on the thin film surface of the stamper by pressing the stamper onto a polymer film for a substrate. And a substrate forming step of forming a substrate for a photoelectric conversion device by transferring the above to the above-mentioned polymer film.

In the master forming process of the invention according to claims 1 and 2, the method of forming the etch pits on the surface of the single crystal silicon is the same as the conventional method, for example, (1)
There is a method of etching single crystal silicon having a crystal orientation of (00) with a strong alkali such as KOH.

On the surface of the single crystal silicon in which the etch pits are formed, silicon oxide (S
A thin film such as iO ₂ ) is formed. Since this thin film is formed by the low temperature film forming method, as described in the prior art, the thin film formed on the top and valley of the etch pit is larger than the thin film formed on the inclined surface of the etch pit. Have defects. When the thin film and the surface of the single crystal silicon are subjected to an etching treatment with an etchant having an etching rate for crystalline silicon higher than the etching rate for the thin film, the thin film formed at the top and the valley of the etch pit has a sloped surface of the etch pit. Since the film characteristics are worse than those of the thin film formed in the above step, they are more likely to be etched by the etching agent, and this etching agent passes through the defects in the thin film and etches the tops and valleys of the etch pits. On the other hand, the film characteristics of the thin film formed on the inclined surface of the etch pit are better than those of the thin film formed on the top and the bottom of the etch pit, and thus are less susceptible to etching by the above-mentioned etching agent. The sloped surface of the etch pit covered with is also less susceptible to etching. Therefore, the tops and valleys of the etch pits are selectively etched, and it is possible to obtain a master for a substrate in which the tops and valleys of the above etch pits are each processed into a curved shape while leaving the texture grooves. Becomes As a material applicable to the thin film, in addition to the above-mentioned silicon oxide, for example, silicon nitride (SiN _x ), tin oxide (SnO ₂ ), titanium oxide (TiO ₂ ), zinc oxide (Z
nO) and the like.

When an etching agent having a lower etching rate for crystalline silicon than a thin film such as silicon oxide is applied as the etching agent, the thin film is uniformly etched regardless of the film characteristics of the thin film. Therefore, it becomes difficult to process the top and valley of the etch pit into a curved shape while leaving the texture groove. Therefore, it is necessary to apply an etching agent having an etching rate for crystalline silicon higher than that for the thin film. Examples of such an etching agent include the following, depending on the type of material forming the thin film. That is, when the thin film is silicon oxide (SiO ₂ ), a highly concentrated alkaline aqueous solution (for example, an aqueous solution of KOH, NaOH, etc.) or a mixed system of HF and HNO ₃ (HF: HNO ₃ = 1: 5 to 5).
1:10), and the thin film is silicon nitride (Si
In the case of N _x ) or titanium oxide (TiO ₂ ), the mixed system of HF and HNO ₃ can be applied. When the thin film is tin oxide (SnO ₂ ), about 5% dilute alkaline (KOH, NaOH, etc.) aqueous solution can be applied, and when the thin film is zinc oxide (ZnO), about 1%. A dilute alkaline (KOH, NaOH, etc.) aqueous solution or the like can be used.

Further, as an etching agent for removing the thin film remaining on the surface of the single crystal silicon after the top and the valley of the etch pit are processed into a curved shape, HF or the like for the silicon oxide thin film is used. About 1% dilute alkali (KOH or NaO) for silicon thin film and titanium oxide thin film
H or the like), an aqueous solution of a strong acid such as hydrochloric acid, sulfuric acid or nitric acid can be applied to the tin oxide thin film, and a diluted acid aqueous solution of about 1% can be applied to the zinc oxide thin film.

Next, as a low temperature film forming method capable of intentionally forming a thin film having poor film characteristics on the top and the valley of the etch pit,
PVD (Physical Vapor Deposition) method such as vacuum deposition method, sputtering method, ion beam devolution method and plasma CV
D method etc. are mentioned.

Regarding the film thickness of the thin film formed on the surface of the single crystal silicon on which the etch pits are formed and the etching treatment time for the thin film and the surface of the single crystal silicon, the depth of the previously formed etch pits is determined. The value may be set to an appropriate value in consideration of the type of the applied etching agent, the curved shapes of the top and valley of the etch pit, and the like.

The substrate master thus obtained is placed on a spinner in the substrate forming step of the invention according to claim 1 and rotated, and then polyimide or the like is placed on the surface of the substrate master. A solution in which a heat resistant polymer (monomer) is dissolved is dropped to form a thin polymer film layer. Then, the polymer film layer is peeled off from the substrate master, and the polymer film layer to which the etch pits of the master are transferred is baked to manufacture a substrate for a photoelectric conversion device. Here, the heat resistant polymer applicable to the invention according to claim 1 and its solvent, solute concentration, etc. are arbitrary,
It is preferable that the rotation speed of the spinner is 10 rotations / minute to 1000 rotations / minute and the solution viscosity is 200 cp to 20000 cp. Further, the firing is performed at a temperature of 100 ° C. to 300 ° C.
C., in air or under an inert atmosphere.

On the other hand, in the stamper forming step of the invention according to claim 2, PVD is applied to the master surface made of crystalline silicon in which the top and valley of the textured groove are processed into a curved shape.
A thin film made of a material having a hardness higher than that of crystalline silicon is formed by an arbitrary film forming means such as a CVD method or a CVD method. Such materials include TiC, diamond, TiB ₂ , ZrB
A material having high hardness and heat resistance such as ₂ can be exemplified. Of these materials, TiC and TiB ₂ thin films are preferred.
The thickness is 1 μm or more, preferably 5 to 20 μm.
Set to about m. Next, a holding material such as stainless steel is attached to the thin film via a glass-based adhesive, and
The master made of single crystal silicon is removed by lapping and etching to form a stamper whose main part is composed of the thin film to which the etch pits of the master are transferred and the holding material. Then, this stamper is set on a roll or pressed in a plate-like shape onto a polymer film for a substrate to transfer the etch pits provided on the thin film surface of the stamper to the polymer film to manufacture a substrate for a photoelectric conversion device. . As the polymer film material for the substrate, a heat resistant polymer material such as polyimide is suitable. Also, a polymer film having a heat distortion temperature of 150 ° C. or higher, preferably 200 ° C. or higher, such as polyphenylene sulfide (PPS) resin, polyethylene terephthalate (PETP) resin, polybutylene terephthalate (PBTP) resin, polyether sulfone, liquid crystal polyester, etc. Can be applied.

As described above, according to the first and second aspects of the present invention, the single crystal silicon whose top and valley are processed into a curved shape while leaving the textured groove as the substrate master is applied. It has an advantage that a polymer film substrate having textured grooves whose tops and valleys are processed into a curved shape can be easily and reliably manufactured.

The polymer film substrate thus obtained can be applied to substrates such as film-forming solar cells and image sensors.

[0023]

According to the first and second aspects of the invention, since the thin film is formed by the low temperature film forming method on the surface of the single crystal silicon in which the etch pits are formed in the master forming step,
The thin film formed on the tops and valleys of the etch pits has more defects than the thin film formed on the inclined surface of the etch pits. Then, when the thin film and the single crystal silicon surface are subjected to an etching treatment with an etching agent having an etching rate for crystalline silicon higher than the etching rate for the thin film, the tops and valleys of the etch pits covered with the thin film having many defects are selectively removed. Since it is subjected to etching, it is possible to prepare a substrate master in which the top and the valley are processed into a curved shape while leaving the texture groove.

Therefore, by applying this substrate master prepared in the master preparing step, it is possible to easily and reliably manufacture a polymer film substrate having textured grooves whose tops and valleys are curved. It will be possible.

[0025]

EXAMPLES Examples of the present invention will be described in detail below.

Example 1 First, a single crystal silicon 1 having a (100) crystal orientation and a thickness of 0.6 mm was immersed in a 5% by weight KOH aqueous solution at 80 ° C. for 20 minutes, and 1.
A 0 to 3.0 μm pyramid-shaped etch pit 10 was formed (see FIG. 1A).

The single crystal silicon 1 having the etch pits 10 formed therein is introduced into a high frequency magnetron sputtering apparatus, and a silicon oxide thin film 2 having a thickness of 0.1 μm is formed on the surface of the single crystal silicon 1 by a sputtering method under the following film forming conditions. A film was formed (see FIG. 1B).

[Film forming conditions] Sputtering target; Si reactive gas type; O ₂ reactive gas supply rate; 1 SCCM to 20 SCCM reactive gas pressure; 1 mTorr to 10 mTorr discharge power; 50 W to 200 W single crystal silicon heating temperature; 100 C.-300.degree. C. Next, the single crystal silicon 1 on which the silicon oxide thin film 2 is formed is etched for about 1 minute using an etching agent of a 30 wt% KOH aqueous solution, and the oxidation formed on the inclined surface of the etch pit 10 is performed. The top and the valley of the etch pit 10 are processed into a curved surface shape through the silicon oxide thin film 22 having poor film characteristics as compared with the silicon thin film 21, and then an etchant of H is added.
Instead of F, an etching process was performed again, and the remaining silicon oxide thin film 2 was dissolved and removed to manufacture a substrate master 3 as shown in FIG. 1 (C).

The substrate master 3 thus obtained
(See FIG. 2A) is placed on a spinner as shown in FIG. 2 (B), and a viscosity (25 ° C.) in which a polyimide monomer is dissolved in methyl ethyl ketone on the surface of the substrate master 3 while rotating at a rotation speed of 50 rpm. ) About 20000 cp of solution was dropped to form a polymer film layer. Then, after the obtained polymer film layer is peeled from the substrate master 3, the polymer film layer to which the etch pits of the substrate master 3 are transferred is subjected to a baking treatment, and the polymer as shown in FIG. The film substrate 4 was manufactured.

Then, the obtained polymer film substrate 4 was applied as a substrate for a film-forming solar cell. That is,
A stainless steel film was formed on the surface of the polymer film substrate 4 by a vapor deposition method to form a back electrode. Next, an amorphous silicon layer consisting of an n layer having a thickness of about 300Å, an i layer having a thickness of about 5000Å and a p layer having a thickness of about 100Å was formed on the back surface electrode by the plasma CVD method under the following film forming conditions. Was deposited.

[Film forming conditions] (1) Type of n layer reaction gas; PH ₃ : SiH ₄ : H ₂ = 0.01:
1:30 reaction gas supply rate; 20 SCCM reaction gas pressure; 100 mTorr power density; 0.13 W / cm ² polymer film substrate heating temperature; 200 ° C. (2) i layer reaction gas type; SiH ₄ reaction gas Supply rate; 30 SCCM Reaction gas pressure; 200 mTorr power density; 0.03 W / cm ² Polymer film substrate heating temperature; 200 ° C. (3) p layer Reaction gas type; B ₂ H ₆ : SiH ₄ : H ₂ = 0.00
5: 1: 100 reaction gas supply rate; 20 SCCM reaction gas pressure; 100 mTorr power density; 0.30 W / cm ² heating temperature of polymer film substrate; 200 ° C. Next, on the p layer of the amorphous silicon layer An ITO film having a thickness of about 700Å was formed by a sputtering method to form a transparent electrode to manufacture a film-forming solar cell.

Then, the film-forming solar cell thus obtained was subjected to current-voltage measurement using a solar simulator of AM1: 100 mW / cm ² , and as a result, V _oc was 0.8.
8 V, J _sc 17.0 mA / cm ² , FF 0.7
The photoelectric conversion efficiency η was 10.6%, which was good.

Further, when the surface reflection characteristics of this solar cell were measured, it was confirmed that the reflectance was reduced over the entire wavelength range and that the light confining action due to the texture groove was functioning.

[Embodiment 2] A substrate master 3 manufactured under the same conditions as in Embodiment 1 is placed in a high frequency magnetron sputtering apparatus, and at room temperature, argon gas is used as a discharge gas and a target is used. Was applied under the conditions of a discharge pressure of 5 × 10 ⁻³ Torr and a discharge power of 5 W / cm ² to form a TiC thin film 51 of about 10 μm on the surface of the substrate master 3 (FIG. 3A). reference).

Next, the TiC thin film 51 heated to 550 ° C.
Glass powder GO17-209 (passivation glass) made by SCHOTT Co., Ltd. is evenly sprinkled on the surface of and melted, and stainless steel 53 having a thickness of 0.5 mm is pressure bonded through this adhesive layer 52. For 10 minutes and then cooled (see FIG. 3B). Then, the substrate master 3 is subjected to a polishing treatment until its thickness reaches about 5 μm, and
The remaining substrate master 3 was etched for about 10 minutes by using an etching agent of HF: HNO ₃ = 3: 5.
A stamper 50 as shown in (C) was created.

Then, the polyimide film 6 having a thickness of 0.5 mm serving as a substrate is heated to 250 ° C.
100 kg using the stamper 50 as shown in (D)
Hot stamping under the pressure condition of / cm ² and stamper 5
The etch pits formed on the surface of the TiC thin film 51 of No. 0 were transferred to the polyimide film 6 to manufacture a polymer film substrate.

Then, a back electrode, an amorphous silicon layer, and a transparent electrode were formed on this polymer film substrate under the same conditions as in Example 1 to manufacture a film-forming solar cell.

The film-forming solar cell thus obtained was AM1: 100 mW / cm ² as in Example 1.
As a result of current-voltage measurement using the solar simulator of Voc, V _oc is 0.88 V and J _sc is 17.0 mA / c.
m ² and FF are 0.71, and the photoelectric conversion efficiency η is 10.
It was as good as 6%.

Further, when the surface reflection characteristics of this solar cell were measured, it was found that the reflectance was reduced over the entire wavelength range, and that the light trapping function due to the texture groove was functioning as in Example 1. It could be confirmed.

[Comparative Example 1] Next, in order to confirm the effect of the polymer film substrate manufactured in the example, single crystal silicon in which the tops and valleys of the etch pits are not processed into a curved shape is used as a substrate master. Using this substrate master, a polymer film substrate made of a polyimide film was manufactured under the same conditions as in Example 2, and using this polymer film substrate, a film-forming solar cell having the same structure as in Example 2 was produced. Was manufactured.

Then, the film-forming solar cell was subjected to current-voltage measurement using a solar simulator having an AM of 1: 100 mW / cm ^{2 in} the same manner as in the example, and the result was V _oc.
Is 0.86 V, J _sc is 17.0 mA / cm ² , FF
Was 0.68 and the photoelectric conversion efficiency η was 9.9%.

When the surface reflection characteristics of this solar cell were measured, the reflectance was reduced over the entire wavelength range,
It was also confirmed that the light confining action due to the texture groove was functioning as in the case of Example 2.

[Comparative Example 2] Similar to Comparative Example 1, in order to confirm the effect of the polymer film substrate manufactured in the example, a curved surface was formed by etching the top and valley of the etch pit without forming a silicon oxide thin film. The single crystal silicon processed into a shape is used as a substrate master, a polymer film substrate made of a polyimide film is manufactured under the same conditions as in Example 2 using this substrate master, and this polymer film substrate is used. A film-forming solar cell having the same structure as in Example 2 was manufactured.

Then, the film-forming solar cell was subjected to current-voltage measurement using a solar simulator having an AM of 1: 100 mW / cm ² as in the example, and as a result, V _oc
Is 0.87 V, J _sc is 16.2 mA / cm ² , FF
Was 0.68 and the photoelectric conversion efficiency η was 9.6%.

When the surface reflection characteristics of this solar cell were measured, the reflectance increased over the entire wavelength range,
It was confirmed that the optical confinement function did not function sufficiently unlike the respective examples.

[0046]

According to the inventions according to claims 1 and 2, by applying the substrate master prepared in the master preparing step, a polymer having textured grooves whose tops and valleys are processed into a curved shape. It becomes possible to easily and surely manufacture the film substrate.

Therefore, it becomes possible to easily form a semiconductor film having few defects and good film characteristics on the surface of the polymer film substrate, and it is possible to improve the photoelectric conversion efficiency of the obtained photoelectric conversion device. is doing.

[Brief description of drawings]

FIG. 1A to FIG. 1C are explanatory views showing a master forming process according to an embodiment.

FIG. 2A to FIG. 2C are explanatory views of a substrate forming process according to the first embodiment.

3A to 3C are explanatory diagrams of a stamper forming process according to the second embodiment, and FIG. 3D is an explanatory diagram of a substrate forming process according to the second embodiment.

4A is a cross-sectional view showing the structure of a film-forming solar cell, and FIG. 4B is a partially enlarged view of FIG. 4A.

FIG. 5 is a conceptual diagram showing film characteristics of a semiconductor film formed on the surface of a polymer film substrate having a high degree of texture.

[Explanation of symbols]

 1 Single Crystal Silicon 2 Silicon Oxide Thin Film 3 Substrate Master 4 Polymer Film Substrate 6 Polyimide Film 10 Etch Pit 21 Silicon Oxide Thin Film 22 Silicon Oxide Thin Film 50 Stamper 51 TiC Thin Film 52 Adhesive Layer 53 Stainless Steel

Claims (2)

[Claims] 1. A method for manufacturing a substrate for a photoelectric conversion device, which comprises a polymer film having textured grooves, wherein a thin film is formed on a surface of single crystal silicon in which an etch pit is formed by a low temperature film forming method, and , The etching rate for the crystalline silicon is higher than the etching rate for the thin film, the thin film and the surface of the single crystal silicon are etched, and the tops and valleys of the etch pits are each processed into a curved surface shape to form a master for the substrate. And a master forming step of forming a polymer film layer on the surface of the master by a spin coating method, and after peeling the polymer film layer from the master, the etch pits of the master are transferred. A step of forming a substrate for a photoelectric conversion device by baking the polymer film layer. Method of manufacturing a photoelectric conversion device substrate according to symptoms. 2. A method for manufacturing a substrate for a photoelectric conversion device, which is composed of a polymer film having textured grooves, wherein a thin film is formed on the surface of single crystal silicon in which etch pits are formed by a low temperature film forming method, and , The etching rate for the crystalline silicon is higher than the etching rate for the thin film, the thin film and the surface of the single crystal silicon are etched, and the tops and valleys of the etch pits are each processed into a curved surface shape to form a master for the substrate. And a master forming step of forming a thin film made of a material having a hardness higher than that of crystalline silicon on the surface of the master, and attaching a holding material to the thin film with an adhesive, and then wrapping the master. And a thin film formed by etching and removing the master etch pits and a holding material. Stamper making process for making a stamper and substrate making process for making a photoelectric conversion device substrate by pressing the stamper onto a polymer film for a substrate and transferring the etch pits provided on the thin film surface of the stamper to the polymer film. A method for manufacturing a substrate for a photoelectric conversion device, comprising: