JPS60176947A - Production of silicon oxide film - Google Patents

Abstract

PURPOSE:To form a transparent substrate, having a silicon oxide film of uneven shape formed on the substrate surface, and suitable for substrates in solar cells, by dipping a base material in a saturated aqueous solution of silicon oxide in hydrosilicofluoric acid containing boric acid added thereto under specific conditions. CONSTITUTION:An aqueous solution of hydrosilicofluoric acid in about >=2mol/ lconcentration is saturated with silicon oxide, and the resultant saturated solution is then diluted with water to prepare a treating solution in about <=2mol/l hudrosilicofluoric acid concentration. An aqueous solution of boric acid is then dropped thereto to supersaturate the silicon oxide, and deposit lumps of the silicon oxide therein. A substrate, e.g. flat glassor plastic sheet, is then dipped in the treating solution while continuing the dropping of an adequate amount of the aqueous solution of the boric acid thereto to bring the treating solution in which the lumps of the silicon oxide are suspended to contact with the substrate surface at 0.2-8cm/min speed to form a silicon oxide film of uneven shape on the substrate surface.

Description

DETAILED DESCRIPTION OF THE INVENTION a. Industrial Application Field The present invention relates to a method for producing a silicon oxide coating on a substrate,
More specifically, the present invention relates to a method of manufacturing a transparent substrate having an uneven shape suitable for a solar cell substrate.

b. Prior Art Today, it is widely practiced to coat the surfaces of various materials with silicon oxide films. For example, it has long been practiced to reduce the reflection effect of the surface by forming alternating multilayer films of titanium oxide and silicon oxide on the glass surface.

Alternatively, it is widely practiced to form a silicon oxide film on the surface of metal/alloy materials as a protective film. Furthermore, when alkali-containing glasses such as soda lime glass or borosilicate glass are used for substrate glass for liquid crystal display panels and solar cells, the surfaces of these glasses are coated with a silicon oxide film in order to prevent the elution of alkaline vacancies from the glass. The coating is carried out with In particular, preventing the elution of alkaline components from glass has become an indispensable technology for maintaining the lifespan of liquid crystal displays or solar cells.

K, which forms a silicon oxide film on the surface of glass, has traditionally been applied by vacuum deposition, sputtering, CVD, or dip coating (
Tipping method) and other methods have been widely used. However, these methods have the disadvantage that the equipment or ancillary equipment is expensive, which increases the cost required for silicon oxide coating, and that only small pieces of glass can be processed.

In view of these drawbacks of the conventional methods for forming silicon oxide films, a new method for forming silicon oxide films has been proposed using a treatment solution in which boric acid is added to a saturated silicon oxide aqueous solution of hydrosilicofluoric acid. (Unexamined Japanese Patent Publication Showa S7-/9 Otsu 7 Guge).

On the other hand, in recent years, solar cells using amorphous silicon (a-3j-), which is produced by glow discharge decomposition of silane gas, are one of the photoelectric conversion devices that can be manufactured at low cost. is bathed in

However, in such an A-8i solar cell, its photoelectric conversion efficiency is higher than that of other crystalline semiconductors (crystalline Si, GaAs, etc.).
In order to solve this problem, various countermeasures have been devised for manufacturing methods and battery structures. In particular, it is necessary to reduce light reflection loss on the surface of the battery and reduce short-circuit current. It is important to increase the amount of light reflected by the solar cell, and for this reason, the solar cell is made to have an uneven structure so that the incident light is reflected within the cell by a multi-reflection layer 1.
] 1, it is considered that the collection efficiency for long wavelength light can be improved. However, if the degree of unevenness is too large, defects such as pinholes are likely to occur, and the film thickness is likely to become non-uniform, which will actually reduce the characteristics of the solar cell (particularly the open circuit voltage and yield rate). Therefore, a highly controlled degree of unevenness was required.

C.Object of the Invention The present invention improves a method for manufacturing a silicon oxide film using a treatment solution in which boric acid is added to a saturated silicon oxide aqueous solution of hydrosilicofluoric acid, which is continuous and inexpensive, and improves the shape accuracy of irregularities. It is an object of the present invention to provide a method for manufacturing a silicon oxide film σ) suitable for a solar cell substrate having an uneven shape, which can be adjusted and manufactured even on a large area.

d.Structure of the Invention The present invention provides a method for producing a silicon oxide coating on the surface of a profiteer by immersing the profiteer in a treatment solution in which boric acid is added to a saturated silicon oxide aqueous solution of hydrosilicofluoric acid. A lump of silicon oxide is floating in the solution, and the weight on the surface of the substrate immersed in the treatment solution is 0.2 to 0.2 g. A method for producing a broken silicon oxide film, which comprises immersing the base material in a treatment liquid while flowing at a flow rate of Ocm, min, to form a silicon oxide film having an uneven shape on the surface of the base material. .

Here, profiteering includes glass, ceramics containing silicon oxide,
Examples include plastic.

Also, the method for adjusting the processing solution used is 2 mol/! - Saturate aqueous solution of hydrosilicofluoric acid with a concentration of 4 or higher and dilute silicon nitride with the appropriate condensate to adjust the concentration of hydrosilicofluoric acid to 1 mol/ml.
It is desirable that it be less than l. The reason why such a treatment liquid adjustment method is desirable is that it increases the film formation rate. The desirable concentration of hydrosilicofluoric acid used as the treatment liquid here is 7 to 2.
mol/l, but rather than directly preparing an aqueous solution of hydrosilicofluoric acid with this concentration and then saturating the silicon oxide, as in the present invention, preparing an aqueous solution of hydrosilicic acid with a high concentration in advance and then saturating the silicon oxide. is saturated, and then the concentration of hydrosilicofluoric acid is l-
This is because diluting with water to 2 mol/e results in faster formation of the silicon oxide film, and the formed irregularities are larger and more numerous.

As boric acid is added to the treatment liquid, silicon oxide gradually becomes supersaturated, and silicon oxide begins to precipitate from the treatment liquid. The method for producing a silicon oxide film of the present invention is a method for obtaining the above-mentioned precipitated silicon oxide as a film.

The addition rate of boric acid is 11 mol/O, S mol/
β and the treatment liquid is a silicon oxide-containing aqueous solution of hydrosilicofluoric acid prepared by the method described in 1. mi, n are preferred. Here, the amount added is O, A> l from OS
't I, I-resistant
When the amount is more than 1n, large silicon oxide particles form in the treatment solution and become precipitates, making it impossible to stably form a silicon oxide film having an uneven shape. In order to obtain a silicon oxide film with a good uneven shape, it is necessary that appropriately sized silicon oxide lumps be suspended in the processing liquid. In addition, the size and number of unevenness in the silicon oxide film that is completed can be changed by the flow rate of the treatment liquid over the substrate surface and the addition rate of boric acid; generally, the slower the flow rate of the treatment liquid, the better the , the faster the addition rate of boric acid, the larger the unevenness becomes.

It is necessary for silicon oxide particles to float in the processing solution due to the flow of the processing solution in order to form a silicon oxide film with a good uneven shape. It is preferable that the solids include silicon oxide solids having a size of /j μm or more. Here/, since a silicon oxide film with a good uneven shape cannot be obtained only by silicon oxide lumps smaller than 5 μm, a flat silicon oxide film can be obtained (Patent Application Showa sg-/3qr/7). It is.

The treatment liquid is made to flow in order to float the precipitated silicon oxide solids in the treatment liquid and mix the added boric acid into the treatment liquid, but the flow rate of the treatment liquid on the immersed surface is 0.2~ g,
Ocm/min is preferred. The flow rate is o, 2
If it is slower than cm7m1n, silicon oxide tends to precipitate in the treatment solution, making it impossible to obtain a silicon oxide film with the desired uneven shape. Furthermore, if the flow rate is faster than Oam/min, the flow tends to become turbulent, resulting in an uneven film, which is not preferable.

Any method may be used to flow the treatment liquid, but a method in which the treatment liquid is flowed out and then circulated using a circulation pump or the like is simple and preferred. Further, it is preferable that the treatment liquid flows in a layered manner with respect to the immersed base phase surface.

This is because when the processing liquid flows turbulently, the film becomes uneven as described above.

The present invention will be explained below based on examples.

e Examples Example 1 Size: 10 (7 (mm) x 100 (mm) Thickness/
(mm) of soda lime glass with O3% concentration (ffii
After immersing the glass in a HF aqueous solution of (t%) for 10 minutes, it was thoroughly washed and dried to obtain a sample glass. Next, prepare an immersion tank for immersing the sample.

The immersion tank consists of an outer tank (1) and an inner tank (2), and the space between the inner tank and the outer tank is filled with water (3). In the experiment, the water was heated with a heater (ψ) so that the temperature of this water was 33"C, and was stirred with an agitator D) to make the temperature distribution uniform. The inner tank was placed in the front part (g). , the middle part (7), and the rear part (g), and inside it there is a treatment solution of 31, which is saturated with silicon oxide in 2 mol/l of hydrosilicofluoric acid and diluted to 1 mol/β by draining the water. The treated liquid in the rear part of the inner tank is not filtered by the circulation pump (/) and is transferred to the front part of the inner tank (B).
be returned to. Here, the ratio of the amount of processing liquid circulated per 7 minutes to the total amount of processing liquid was set to g%. (Here, the total amount of treated liquid is about 34 cm, and the bottom area of the middle part of the processing tank is about 130 cm2.
Therefore, the liquid flow rate on the surface of the substrate glass plate to be immersed is approximately 1. It is expected to be tcm7m1n. ) liquid (//) to 0.
It was continuously dropped at 2m/7min and held for 70 hours.

Thereafter, a sample (9) is vertically immersed and held in the reaction solution in the center part (7) of the inner tank. Circulation of the reaction solution and addition of the aqueous boric acid solution were continued for 1 hour, after which the sample was taken out, washed and dried.

The thickness of the obtained coating was approximately 100 qA, and the results of electron microscopic observation of the coating were shown in Figure 2: Diameter: 300~J; 0OOA, Height: 2.

The shape of the unevenness and the number per crown area can be expressed as the degree of scattering (haze rate) for incident light as a comprehensive effect. The haze rate of the sample obtained here was determined by the Haze Value Measuring Method for Methacrylic Resin Boards for Aircraft (JIS, 6-6).
7/Z (/977)), it is about 2%,
This was a large value compared to the Heis ratio of 0.2% for the sample coated with 5102 film, which has no irregularities on the surface.

Except that the circulation rate of the treatment liquid was changed to 1JJ:vc of the total treatment liquid per 7 minutes @L3% (flow rate of treatment liquid approximately 0.Cm/m1n), and the immersion time of the sample was changed to 3 hours. A silicon oxide film with a thickness of about 1000A was formed on each sample by the same method as in Example.

? J et al., 11 The silicon oxide film is a film with a thickness of about 1000X, and by electron microscopy observation of the sample, it was observed that the sample had a diameter of 300mm, similar to Example 1. ;000A height, 200~3
It is certain that there are many roughly bowl-shaped irregularities of 000A.

In addition, the heis ratio of the sample was 7%, Example 2
(The sample obtained by this method was higher than the sample obtained by Example/by the increase in the ratio of unevenness with deep arcs or the number of unevenness by 11
It is expected that it will be 1~.

Example 3 A substrate glass with a silicon oxide film having an uneven shape (hereinafter referred to as AO) manufactured in Example 2 was treated with a silicon oxide forming solution containing phosphorus (OCD solution manufactured by Tokyo Ohka-L Gyo Co., Ltd.). immersed, then baked in soo'c to a film thickness of about 1000
A large silicon oxide film was formed.

(Hereinafter, this substrate will be referred to as AI and lPp.) The heis ratio changed from 7% to 3%.

Similarly, about 20
Silicon oxide film thickness of OA +1! , forming 1-%. (Hereinafter, this board will be referred to as A2) The Heis ratio changed from oJ7% to Otsu%.

Separately, a glass substrate similar to Example Ω was immersed in an unsaturated aqueous solution of hydrosilicofluoric acid with boric acid added to it.
- Comparative substrate B was prepared using 1000λ of silicon oxide forming liquid with high smoothness (Tokuo 1 Showa 5g-7372/7) Using these substrates, a 1 m thick amorphous S coat,
'lLG was created. The creation procedure is shown below.

On the substrate A O+ A ], + A2 + B, an air of monofiltrate 8 trichloride and an as a dopant:
A 2000A tin oxide transparent conductive film was formed by CVD using \0HF2 residue. Next, monosilane (S)
, H4) 10OP using raw material waste whose main component is gas
(1) P-type semiconductor layer (boron 1'-) (1) a-3 using a capacitively coupled high-frequency glow discharge device under a pressure of about a
IC'Hr was prepared by vapor deposition in order C (deposition, finally A/set of electrodes about 50X) in vacuum (about 10-4 Pa).

100 mW/Cm2 (1
') Electromotive force (open circuit voltage) when light is irradiated and the load is infinite.

(2) and the current value per unit surface area of the solar cell (short circuit current; m4/Cm2) when the load was O.

Table 1 shows the measurement results obtained. As is clear from the table, substrates A O, A using a silicon oxide film with an uneven shape
, l + A, 2 showed a larger short-circuit current value than the substrate B using a smooth silicon oxide film, indicating that the performance was improved.

Here, in the above embodiment, glass containing silicon oxide was used as the base material, and the shape was 100 mm x 100 mm, and the size of the plate was 9 loaves. However, since the surface film is an adhesive film, it is possible to use all kinds of materials such as colored glass, other strength glass plates, plus sack analysis, and mixed rice. can. Also the shape/
00 mm
M material can be immersed.

f. Effects of the Invention According to the present invention, it is possible to easily form a silicon oxide coating having an uneven shape with the accuracy of the unevenness adjusted on a large plate-shaped base material. The silicon oxide covering body having the uneven shape formed in this way can be used as a solar cell substrate when the base material is a transparent material. / No. 39 → 'MHj Compensation-□-1-C Name of the invention Method for manufacturing silicon oxide film 3 Relationship to the case of the person making the amendment Patent applicant address 4-8 Doshomachi, Higashi-ku, Osaka-shi, Osaka Name Name
(goo) Shin Saiga, Representative of Nippon Sheet Glass Co., Ltd.
Ogu agent 2 Target of correction Details, -1=12N and brief explanation" column.

7 In the Supplementary Contents Specification, page 1S, lines 7 to 11, it says "Figure 2 is an electron micrograph." This is an electron micrograph in place of a drawing showing the structure of approximately bowl-shaped particles formed in a silicon coating. Correct it to 1.

Claims (3)

[Claims] (1) In a method of manufacturing a silicon oxide film on the surface of a substrate by immersing the substrate in a treatment solution in which boric acid is added to a saturated aqueous solution of silicon oxide of hydrosilicofluoric acid, the method includes: The substrate is immersed in the treatment liquid in a state in which lumps of silicon oxide are suspended in the treatment liquid and the treatment liquid flows at a rate of 0.2 to OCm/min on the surface of the immersed substrate. 1. A method for producing a silicon oxide film, comprising forming a silicon oxide film having an uneven shape. (2) The method for producing a silicon oxide film according to claim 1, wherein the flow of the treatment liquid is a laminar flow parallel to the surface of the substrate immersed. (3) The flow of the processing liquid is caused by the outflow operation and circulation operation of the processing liquid, or (4) the silicon oxide coating having the uneven shape has a diameter of 300 to 500 mm.
4. The method for producing a silicon oxide film according to claim 1, wherein the film has a large number of convex portions with an Xy height of 200 to 3 oooA.