JPS62219969A - Manufacture of semiconductor photodetector - Google Patents

Abstract

PURPOSE:To improve reflection characteristics and improve the production yield by a method wherein, after the uneven surface of a TCO (transmitting conductive oxide) layer is polished without substantial change of the unevenness, a semiconductor film including an optical active layer is contacted with the uneven surface and the TCO layer with the uneven surface is utilized as a light detecting electrode. CONSTITUTION:A TCO layer 2, whose average particle diameter is about 500-2,000Angstrom , is applied to the flat insulating surface of a light transmitting support substrate 1 by a method such as spray. Then etching is carried out from the exposed surface of the TCO layer 2 into the substrate 1 until the halfway of the thickness direction to give the exposed surface fine unevenness. Then the uneven surface (2 tex) of the substrate is subjected to polishing in such a manner that the unevenness is not significantly changed. Then layers of fine crystalline silicon or the like are laminated on the uneven surface whose sharp protrusions, steps and the like are relieved by optical CVD with silicon compound gas such as SiF4 to form a semiconductor film 3 of PIN junction type, P-N junction type, P-I junction type or tandem structure of those types which includes an optical active layer creating optical carriers.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing semiconductor light receiving devices such as solar cells and optical sensors that output light energy as magnetic energy.

(c4 Prior art □ A semiconductor light receiving device in which a light receiving surface, a semiconductor photoactive layer, and a surface electrode are deposited in this order on a transparent substrate such as glass is disclosed in, for example, Japanese Patent Publication No. 53-37718 and the United States. This is already known as disclosed in Japanese Patent No. 4,281,208.The light-receiving surface electrode is usually formed using an oxidized film formed by electron beam evaporation, vacuum evaporation, sputtering, CVD, spraying, or the like. Transparent conductive oxides (indium tin CITO) and tin oxide (SnOx)4
TC01 below.

(referred to as ) is used.

However, if the light-receiving surface electrode is formed from such TC・0,
The refractive index of this TCO is about 2.0, whereas the refractive index of the semiconductor photoactive layer in contact with it is higher than 2.0.For example, amorphous silicon such as amorphous silicon, amorphous silicon carbide, amorphous silicon germanium, etc. For system semiconductors, it is around 4.0, so the light incident from the support board side is reflected at the interface between the light-receiving surface electrode and the photoactive layer based on the difference in refractive index, resulting in photoelectric conversion. This caused a reduction in the amount of light incident on the active photoactive layer.

1985 Spring Proceedings of the Japan Society of Applied Physics No. 439, page 29-
In the prior art disclosed in U-14, in view of the fact that the reflection characteristics at the interface between the light-receiving surface electrode and the photoactive layer are significantly affected by the shape of the interface, the surface of the light-receiving surface electrode on the photoactive layer side is made uneven. It is proposed to increase the light haze incident on the photoactive J-.

Similarly, attempts to make the surface of TCO skin uneven have been made, for example, in JP-A-59-123279 and JP-A-59-16.
It has been actively researched in recent years, as seen in Japanese Patent Application Laid-open No. 1882, Japanese Patent Application Laid-open No. 59-159574, and Japanese Patent Application Laid-Open No. 59-201470. Figure 8 shows the measured reflection characteristics of a support substrate with Te3 adhesion that has an uneven surface and a support substrate with TCOJm adhesion that has a flat surface. TCOJI on uneven surface
The broken line shows the reflection characteristics of the TCO pigeon with a flat surface. As is clear from FIG. 8, the TCO skin on the uneven surface has a low reflectance in the approximately visible light band of about 400 nm to 800 rL[n, especially in the long wavelength band of about 6 QQ nm or more. The reflection characteristics have been improved.

However, by arranging the support substrate with the TCO/II with the uneven surface on the light-receiving surface side of the semiconductor light-receiving device and using the TCOs as the light-receiving surface electrode, the reflection characteristics can be improved. Although more light can be guided to the semiconductor photoactive layer, there is a drawback that the manufacturing yield is lower than that of a device in which a flat 700 layer is used as one light-receiving surface.

(c) Problems to be Solved by the Invention The present invention attempts to simultaneously improve the reflection characteristics by using TC(]- with an uneven surface as a photoreceptor and to improve the manufacturing yield, which are contradictory requirements. It is something to do.

B) Means for Solving the Problems The present invention aims to solve the above-mentioned problems by using
A support substrate with a 0 layer attached is prepared, and the uneven surface of the 700 layers is polished without significantly changing the uneven state, and then a semiconductor film containing photoactive J- is contacted with the uneven surface. It is characterized by being forced.

(e) Effect By polishing the uneven surface of <700 layers as described above without significantly deforming the uneven state, sharp protrusions and convexities that were locally occurring on the uneven surface can be removed. Edges and even sharp differences are alleviated.

(F) Embodiment FIGS. 1 to 1@5 show an embodiment of the manufacturing method of the present invention, to FIG. 3 show an example of the uneven processing process of TCOt, which is typified by ITO and 5nOx. First, as shown in FIG. 1, a layer is formed along a substantially flat insulating surface of a transparent supporting substrate (1) such as glass by a well-known electron beam evaporation method, vacuum evaporation method, sputtering method, CVD method, spray method, etc. An electrode substrate is prepared on which a TCO layer +21 having an average particle size of about 50 to 2000 Å is deposited. .

The above 700 layers (21 are, for example, 4 x
It is made of ITO doped with 5% 5nOx obtained by a beam evaporation method, and is approximately 500-2000A as described above.
The film has an average particle size of 1,500 to 7,000 Å in thickness.

In the process shown in FIG. 2, the TCOm (21) deposited along the substantially flat surface of the support substrate (1) is etched from its exposed surface toward the support substrate (1). As an etching solution, the above-mentioned ITO TCOJI is used.
HCL:H2O:FeCl3-50 for II(2)
0cc: 600cc: 1009 is suitable, and aqua regia can also be used. In such an etching process, although the 700 layer (2) is sequentially etched away from its exposed surface, due to the anisotropy of the etching rate of TCOm (21), the etching rate is high as shown in FIG. Since etching starts from that part, the cross section becomes trapezoidal.

FIG. 3 shows a state in which the etching process shown in FIG. 2 has been completed. That is, such etching treatment is performed using TCOJII (
2) until the exposed surface has fine irregularities suitable as a light-receiving surface electrode of a photovoltaic device. ~10,000 TCOjm (2+) is formed with an approximately triangular pyramid-shaped uneven surface (2tex). Uneven surface (2
tex) is obtained.

The reflection characteristics of the supporting substrate (1) with such an uneven surface (2 tex) are as shown by the solid line in Fig. 8, where a low reflectance is seen on the long wavelength side of the visible light band, and the transmission is low. efforts are being made to improve the ratio.

In the step shown in FIG. 4, the uneven surface (2 tex) of the support substrate (1) whose reflection characteristics have been improved is polished. What must be kept in mind in this polishing process is that TC
O layer (2) uneven surface (2t ex) (7) The uneven state should not be significantly deformed. In other words, the uneven surface (2t ex)
If polishing is performed until the uneven state of the surface (tex) is significantly deformed, in other words, until it is almost flat, the reflection characteristics cannot be improved. Therefore, in the present invention, it is important not to significantly deform the uneven state, which is closely related to the reflection characteristics, in the polishing step (2) as described above. Since such changes in the uneven state depend on the polishing material used and polishing conditions such as polishing time, pressure, and polishing speed, it is necessary to experimentally determine the optimal polishing conditions depending on the polishing material used in advance. , based on those conditions.

Figure 6 shows the relationship between the reflection characteristics and polishing time when using a polyurethane polishing cloth with a foamed surface that does not pose the risk of remaining like polishing powder on an uneven surface (2 tex) as a polishing material. The figure (A) shows the reflection characteristics before polishing, and the figure (B) shows the reflection characteristics after 10 minutes of polishing.
Figure (C) shows the reflection characteristics after a polishing time of 30 minutes. The polishing conditions other than the polishing time were the same, and the pressure was 2.
1/d, rotation a (speed) 10 (1 rpm).

As a result of these measurements, when polishing cloth made of foamed polyurethane was used as the polishing material, polishing with the above polishing conditions for 10 minutes had almost no effect on the reflection properties, but polishing for 30 minutes caused long wavelength An increase in reflectance was observed in the band. Therefore, with the above-mentioned polishing material and polishing conditions, the polishing time should be less than 30 minutes to prevent the uneven state from being significantly deformed.

On the other hand, when examining the relationship among polishing conditions such as polishing time, pressure, and polishing rate, it is found that as described above, when the pressure and polishing rate are constant, the polishing state progresses as the polishing time increases. Similarly, if the polishing speed increases when the polishing time and pressure are constant, the polishing state also progresses.

Furthermore, the polishing state progresses in the same way when the pressure increases.

That is, any one of polishing time, pressure, polishing speed, etc. is in a proportional relationship with the polishing state when the other two conditions are constant. Therefore, the present inventors conducted various experiments on the polishing conditions when using the foamed urethane polishing cloth as the polishing material, and found that □ Polishing time was approximately 5 to 25 minutes, pressure was 5 to 30 P/d, and the number of revolutions ( Polishing speed) 20~l 5
The range of Q rpm was found.

In the process shown in Fig. 5, the uneven surface of the TCO pigeon (2) has been softened from the steep protrusions, sharp protrusions, and sharp differences that were locally generated in the polishing process. 2tex), the aforementioned Japanese Patent Publication No. 53-57718 and U.S. Patent No. 4
, 281, 208, 5iH4
Amorphous silicon, amorphous silicon carbide, amorphous silicon germanium, microcrystalline silicon, etc. are appropriately placed in each layer by plasma CVD or photoCVD using silicon compound gas such as jsi2H4eSiF4 as the main raw material gas, and photoactivation is performed to generate photocarriers. PIN junction board with layers, PN junction type, Pi junction type,
Or a tandem structure with a film thickness of 5000A to several μm
While forming the semiconductor film (3), the semiconductor film (3)
AI on top! Single layer structure, AI! /Ti laminated structure or T
A surface electrode (4) of a CO/highly reflective metal (AIF, AI!, etc.) laminated structure is provided.

FIG. 7 shows a semiconductor light receiving device in which a semiconductor film (3) including a photoactive layer is brought into contact with the uneven surface (2 tex) of the TCO dove (2), and then a surface electrode (41) is arranged, based on the manufacturing method of the present invention. Remains in the polishing process during manufacturing (%)
This study investigated the relationship between That is, as before, TC
Onorra (21) A semiconductor photodetector device that does not polish the uneven surface (2 tex) (polishing time 0 minutes) has a photoelectric conversion efficiency of about 9.5%, which is a reasonable characteristic, but the manufacturing yield is low. The ratio was as low as about 72%, leading to a lack of salmon productivity.In contrast, using the foamed polyurethane polishing cloth detailed in the above example, the pressure was 20F/d and the number of revolutions was 1.
When polishing was performed under the polishing conditions of 100 rpm, the manufacturing yield improved to over 90% in a polishing time of 5 minutes, and after that, the manufacturing yield improved to over 90%.
Even in samples polished for up to 50 minutes at minute pitches,
Yields increased in all cases. On the other hand, the photoelectric conversion efficiency exceeded 11% during the polishing time of 10 to 20 minutes, and an extremely high conversion efficiency could be obtained. Such an improvement in photoelectric conversion efficiency η is due to the window m (in the case of a pin junction type, P made of a thin and wide bandgap material) that directly contacts the uneven surface (2 tex) and guides more light to the photoactive skin. )
This is thought to be due to improved film quality and non-uniformity of the junction electric field at the interface between the window and the photoactive layer.

(G) Effects of the Invention As described above, the manufacturing method of the present invention polishes the uneven surface of the TCO shield without significantly deforming the uneven state, thereby removing sharp edges locally occurring on the uneven surface. The sharp edges of protrusions and convexities, as well as sharp differences in angles, are alleviated, so the use of TCO+w with such an uneven surface as a light-receiving surface electrode improves the reflection characteristics and improves manufacturing yield, which is a conflicting requirement. can be achieved at the same time.

Further, it is possible to improve the film quality of the semiconductor film that is in direct contact with the uneven surface and to improve the internal junction electric field, and it is also possible to increase the light conversion efficiency.

[Brief explanation of drawings]

Figures 1 to 5 are cross-sectional views schematically showing the state of each step of the manufacturing method of the present invention, and Figures 6 (A) to (C) show the relationship between polishing time and reflectance in the polishing process. Figure 7 is a characteristic diagram showing the relationship between polishing time, photoelectric conversion efficiency (η), and manufacturing yield, and Figure 8 is a reflection characteristic diagram showing the relationship between polishing time, photoelectric conversion efficiency (η), and manufacturing yield.
The reflection characteristics of TCoJIil+ with a layer and a flat surface are shown, respectively. (1) Support substrate, (2) Transparent conductive oxide (TCO) skin, (2tex) Uneven surface, (3)
...Semiconductor layer, (4)...Surface electrode.

Claims (3)

[Claims] (1) A supporting substrate with a transparent conductive oxide layer having an uneven surface is prepared, and the uneven surface of the transparent conductive oxide layer is polished without significantly changing the uneven state. After that, a semiconductor film including a photoactive layer is brought into contact with the uneven surface. (2) The method of manufacturing a semiconductor light receiving device according to claim 1, wherein a polishing cloth is used in the step of polishing the uneven surface of the conductive oxide layer. (3) The method for manufacturing a semiconductor light receiving device according to claim 2, wherein the surface of the polishing cloth is in a foamed state.