JPH0447466B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a method of manufacturing an optical semiconductor device such as a photovoltaic device or a photoconductive device.

<Background Art> Devices of this type using a semiconductor film such as amorphous silicon for the photosensitive layer are already known.

FIG. 1 shows a conventional optical semiconductor device using an amorphous semiconductor film, in which 1 is a transparent substrate, 2a, 2b, 2
c... are transparent conductive films deposited on the substrate 1 at regular intervals; 3a, 3b, 3c... are amorphous semiconductor films superimposed on each transparent conductive film; 4a, 4b, 4c...
is a back electrode film which is superimposed on each amorphous semiconductor film and partially overlaps each transparent conductive film 2b, 2c, . . . on the right.

Each of the amorphous semiconductor films 3a, 3b, 3c, .
When light is incident sequentially through , a photovoltaic force is generated. The photovoltaic forces generated within each of the amorphous semiconductors 3a, 3b, 3c, .

In such a device, one factor that influences the light utilization efficiency is the total area of the amorphous semiconductor films 3a, 3b, and 3c that actually contribute to power generation, relative to the light receiving area (i.e., substrate area) of the entire device. This is the proportion of However, each amorphous semiconductor film 3a, 3b, 3
A region without an amorphous semiconductor (a region indicated by the symbol NON in the figure) that inevitably exists between adjacent regions of c... reduces the above-mentioned area ratio.

Therefore, in order to improve the light utilization efficiency, first, the distance between adjacent transparent conductive films 2a, 2b, 2c, etc. is reduced,
Then, the distance between adjacent amorphous semiconductor films 3a, 3b, 3c, . . . must be reduced.

This kind of spacing reduction is determined by the processing accuracy of each film,
Therefore, conventionally, photo-etching technology, which has excellent precision machinability, has been used. In the case of this technique, the process of depositing a transparent conductive film on the entire surface of the substrate 1, and the separation of each individual transparent conductive film 2a, 2b, 2c, etc. by photoresist and etching, that is, each transparent conductive film 2a, 2b, 2c...; a step of depositing an amorphous semiconductor film over the entire surface of the substrate 1 including on each of these transparent conductive films; and a step of removing each individual amorphous semiconductor film 3 by photoresist and etching.
A, 3b, 3c, .

However, although photo-etching technology is excellent in terms of fine processing, it tends to cause defects in the amorphous semiconductor film due to pinholes or peeling at the periphery of the photoresist that defines the etching pattern.

The prior art disclosed in Japanese Unexamined Patent Publication No. 12568/1987 provides the above-mentioned adjacent spacing by burning out the film by laser irradiation, and this technique, which does not use any photoresist required in photolithography, solves the above-mentioned problems. It is extremely effective in solving problems. Moreover, each amorphous semiconductor film 3a, 3b, 3 obtained by photolithography
The adjacent spacing between c... is about 600 μm, but if a laser is used, the spacing can be made even smaller.

When using a laser, it is important to keep in mind that if there is another film under the part of the film to be burnt out,
Do not damage it. Otherwise, not only the desired portion of the membrane will be burned off, but also the underlying membrane that is not needed will be burned off. The above prior art is
In order to meet this requirement, it is proposed to select the laser output and pulse frequency for each film.

However, it is difficult to stabilize the laser output or pulse frequency, and considering that the various thicknesses in this type of device are very thin, it is difficult to stabilize the laser output or pulse frequency. methods to prevent damage are not optimal.

<Disclosure of the Invention> The present invention utilizes a laser, and in an optical semiconductor device consisting of a superimposed body of a transparent conductive film and a semiconductor film, the present invention focuses on the difference in light absorption characteristics of each of these films. is used.

Figure 2 shows the relationship between the light wavelength and the absorption rate of the film, where the solid line represents the absorption rate of amorphous silicon, and the broken line represents the absorption rate of the transparent conductive film (tin oxide film). There is. Therefore, for example, if a transparent conductive film is irradiated with a laser beam with a wavelength of around 1 μm, the absorption rate of the transparent conductive film to the laser beam is at its peak, so the transparent conductive film in the laser irradiated area can be easily removed. can do. On the other hand, if a laser beam with a wavelength of approximately 0.6 μm is irradiated to an amorphous semiconductor film to partially remove it, the absorption rate for the laser beam will be:
Since the transparent conductive film has a much lower resistance than the amorphous semiconductor, the transparent conductive film is less likely to be damaged by the laser irradiation.

The present invention is based on such a novel idea, and its characteristics can be summarized as follows: After the unnecessary portion of the transparent conductive film is removed by irradiating the laser beam of the first wavelength, the unnecessary portion of the semiconductor film is removed. at least a portion of the transparent conductive film is partially removed by irradiating the transparent conductive film with a laser beam of a second wavelength whose light absorption rate is sufficiently lower than that of the semiconductor film,
The point is that a portion of the transparent conductive film is exposed.

In carrying out the present invention, amorphous semiconductors such as amorphous silicon, amorphous germanium, amorphous silicon nitride, and other amorphous semiconductors are used as semiconductor films, and tin oxide is used as a transparent conductive film. A film, a tin oxide/indium film, etc. are used.

The method of the present invention can also be implemented in conjunction with the laser power and pulse frequency selectivity disclosed in the prior art.

<Example> FIGS. 3 to 3F show a method according to an embodiment of the present invention in the order of steps. In the process shown in Figure 3A, the thickness is 1 mm to 3 mm.
The entire surface of the transparent glass substrate 10 is coated with a thickness of 2000 Å or more.
A transparent conductive film 11 of 5000 Å of tin oxide is deposited.

In the step shown in FIG. 3B, the adjacent spacing portions 11' are removed by laser beam irradiation, and the individual transparent conductive films 11a, 11b, 11c, . . . are formed separately. The laser used has a wavelength of approximately 1.06μm and an output of 1.3×10 ⁸ W/
cm ² and a YAG laser with a pulse frequency of 3 KHz is suitable, and the spacing L ₁ between adjacent spacing portions 11' is set to about 100 μm.

In the step of FIG. 3C, each transparent conductive film 11a, 1
An amorphous silicon film 12 having a thickness of 5000 Å to 7000 Å is deposited on the entire surface of the substrate 10 including the surfaces 1b, 11c, . . . . Such a silicon film contains a PIN junction parallel to the film surface within it, and therefore, more specifically, a P-type amorphous silicon film is first deposited, and then an I
Type and N type amorphous silicon films are deposited in sequence.

In the process shown in FIG. 3D, the adjacent spacing portions 12' are removed by laser beam irradiation, and individual amorphous silicon films 12a, 12b, 12c, . . . are formed separately. The laser used has a wavelength of 0.51 μm and an output of 2×
A 10 ³ W/cm ² CW Ar laser is suitable, and the spacing L ₂ between adjacent spacing portions 12' is set to about 300 μm.

At this time, the laser light finally reaches the transparent conductive film portion 110 that exists under the adjacent spacing section 12', but it should be noted that the absorption rate of light at the current wavelength is as shown in FIG. As shown, the transparent conductive film has a much lower resistance than the amorphous silicon film. Therefore, if the laser beam is scanned with an irradiation time long enough to remove the amorphous silicon film 12 by the thickness thereof, the thickness of the amorphous silicon film 12 will be completely removed. As a result, even if the laser beam temporarily hits the transparent conductive film portion 110 directly, that portion will hardly be damaged.

In the process shown in FIG. 3E, a thickness of 200 Å to 1 μm is applied to the entire surface of the substrate 10, including the transparent conductive film portion 110 and each surface of the amorphous silicon films 12a, 12b, 12c, .
A back electrode film 13 made of thick aluminum is deposited.

In the final step shown in FIG. 3F, the adjacent spacing portions 13' are removed by laser beam irradiation to form individual back electrode films 13a, 13b, 13c, . . . . The laser used has a wavelength of approximately 1.06 μm and an output of 5×
A YAG laser with a power of 10 ⁶ W/cm ² and a pulse frequency of 3 KHz is suitable, and the distance L ₃ between adjacent space parts 13' is approximately 20 μ.
m.

The melting point of aluminum, which is the material of the back electrode film 13, is very low compared to that of the transparent conductive film 11. Therefore, a laser with an output value sufficiently lower than that used to separate the transparent conductive films 11a, 11b, and 11c is required. It should be noted that it is used. Therefore, when the laser beam is scanned with a sufficient irradiation time to remove the back electrode film 13 by the thickness thereof, the back electrode film 13 is completely removed by the thickness, and as a result, the back electrode film 13 is temporarily removed. Even if the laser beam were to directly hit the transparent conductive film portion 110, that portion would hardly be damaged.

Note that when removing such a portion of the back electrode film 13, only the desired portion of the back electrode film 13 can be removed more reliably by applying black ink or the like to the surface of the removed portion to promote absorption of laser light. be able to.

The various numerical values listed in the above embodiments are merely exemplary and can of course be changed as appropriate. For example, each of the transparent conductive films 11a, 11b, 11c
The interval between ... may be about 20 μm.

<Effects> According to the present invention, when manufacturing an optical semiconductor device including a transparent conductive film and a semiconductor film deposited thereon, partial removal of the transparent conductive film and partial removal of the semiconductor film are performed. To easily remove a portion of a transparent conductive film by properly using the wavelength of a laser that performs this, and to ensure partial removal of a semiconductor film by laser without damaging other films. This makes it possible to effectively utilize ultra-fine processing using a laser.

[Brief explanation of the drawing]

Figure 1 is a side view of a typical optical semiconductor device, Figure 2 is a side view of a typical optical semiconductor device;
The figure is a light absorption characteristic diagram, and FIGS. 3A to 3F are process-by-step side views showing an embodiment of the present invention. 11a, 11b, 11c...transparent conductive film, 12
a, 12b, 12c...Amorphous semiconductor layer.

Claims (1)

[Claims] 1. When manufacturing an optical semiconductor device comprising a transparent conductive film and a semiconductor film coated on the conductive film and sensitive to light transmitted through the film, an unnecessary portion of the transparent conductive film is exposed to a laser beam of a first wavelength. After being removed by irradiation with light, at least a portion of the unnecessary portion of the semiconductor film has a thickness of 0.6 μm, which has a light absorption rate for the transparent conductive film that is sufficiently lower than that for the semiconductor film.
A method for manufacturing an optical semiconductor device, characterized in that the transparent conductive film is partially removed by irradiation with a laser beam of a second wavelength as described below, and a portion of the transparent conductive film is exposed.