JPS61170077A - Manufacture of thin-film solar cell - Google Patents

Abstract

PURPOSE:To increase an effective area to 95% or more by using laser machining not only on the isolation of a transparent electrode and a semiconductor active layer but also on the isolation and formation of a metallic electrode. CONSTITUTION:Transparent electrodes 21-23 and amorphous silicon layers (a-Si layers) 31-33 isolated and shaped through laser machining are laminated onto a glass substrate 1, a metallic film 4 is applied onto one surface, and the amorphous silicon thin-films and the metallic films are laser-machined simultaneously. Crystallized silicon layers 91, 92 remain under isolation grooves 81, 82 at that time, and generating regions are isolated incompletely. The crystallized silicon layers 91, 92 are etched while using metallic electrodes 41-43 completely isolated by processes up to that time as masks. Accordingly, the layers 91, 92 can be removed approximately perfectly.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention provides a transparent conductive film on a translucent insulating substrate.
m71-yfApoPurchaseTemu1muP = Stacked in U sonoshin, and at that time, by sequentially shifting the position of each separation part, the transparent electrode, semiconductor active layer and metal electrode are formed, and they are mutually stacked. The present invention relates to a method of manufacturing a thin film solar cell that forms a plurality of power generation regions connected in series.

[Prior art and its problems]

Thin-film solar cells are being actively researched for practical application because they can be manufactured at low cost, and are already widely used as power sources for consumer devices. However, since the output of amorphous silicon solar cells is about 0.9V at most, it is necessary to connect a plurality of these in series. FIG. 2 shows a cross-sectional view of a solar cell according to a conventional manufacturing method, in which transparent electrodes 21, 22, and 23 are separately formed on a glass substrate 1. Furthermore, on top of that, an amorphous silicon layer 31, 32
．． 33 is separated and formed. This amorphous silicon layer includes, for example, zero-order metal electrodes 41, 42, .
Form 43. This metal electrode needs to be formed so as to be electrically connected to the transparent electrode in the adjacent area. For example, the metal electrodes 41 and 42 are connected to the transparent electrodes 22 and 23, respectively. In this way, the punishment can be achieved by applying a mask or by etching after coating the entire surface. The region A from the right end of the electrode 8i+21 to the left end of the metal electrode 42 is a region where no power is generated.When the power generation region is separated by the mask method, the width of this non-power generation region A needs to be about 2fi to avoid short circuits. On the other hand, since the width of the power generation region B is about 10a at most due to the restriction due to the resistance loss of the transparent electrode, the ratio of the area of the power generation region to the total area, that is, the effective area ratio, is about 83%.Also, the photoetching method If , this value would be improved to over 90%, but the number of steps would increase accordingly, so it is not a good idea.In recent years, lasers have been used that can improve the effective area ratio and perform highly accurate processing. A buttering method has been put into practical use. Figure 3 is a cross-sectional view showing the process. Figure 3 (fat) is a cross-sectional view after separation of the amorphous silicon layer. On glass substrate 1 After uniformly forming transparent electrodes on the substrate, grooves 51 and 52 are formed using a laser and separated.Furthermore, an amorphous silicon layer is formed thereon, and grooves 6 are formed using a laser as well.
1.62 is formed, and then a metal electrode is formed separately, but it has become clear that etching with a laser is extremely difficult in this case. This is because metals generally have high thermal conductivity, so irradiation with laser light crystallizes the underlying amorphous silicon layer and lowers the resistance. As a result, the metal electrodes 41 and 42 become short-circuited at the portion $Tl shown in FIG. 3(g) 1, for example, and no photocurrent can be extracted. To prevent this,
It is conceivable to use a conventional method for etching only the metal electrode, but then the original purpose, that is, the effect of improving the effective area ratio, will be halved.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing a thin film solar cell in which laser processing can be applied to the separation formation of not only transparent electrodes and semiconductor active layers but also metal electrodes, and the effective area ratio is improved.

[Key points of the invention]

According to the present invention, a transparent electrode separated by a laser beam and a metal film completely deposited on a semiconductor active layer are separated by a laser beam to form a metal electrode, and most of the underlying semiconductor thin film is also removed. The above object is achieved by removing the remaining semiconductor thin film by plasma etching or chemical etching using the metal electrode as a mask.

[Embodiments of the invention]

FIG. 1 fat, (bl, (cl) is a cross-sectional view for explaining the process of one embodiment of the present invention, and FIG. After laminating the separately formed transparent electrodes 21, 22, 23 and the amorphous silicon layer (a-5 rich layer) 31, 32, 33, a metal film 4 is deposited on the - side.Transparent electrode 2
1.22.23 is known as a transparent conductive material,
5nOt or ITO formed by a vapor deposition method or the like is used. The amorphous silicon layers 31, 32, and 33 are made of, for example, p-type amorphous silicon obtained by glow discharge decomposition of a mixed gas of diborane (B!Hi) and monosilane (SIH), and glow discharge of SiH. It has a three-layer structure of i-type amorphous silicon, which is obtained by 5IH4, and n-type amorphous silicon, which is obtained by glow discharge of 5IH4 and phosphine (PHs). The thickness of each layer is 100, 4000, and 3, respectively.
Selected by 00 people. The metal film 4 is, for example, a vapor-deposited film of aluminum formed to a thickness of about 1 inA. After forming this metal tl 14, in the present invention, the amorphous silicon thin film and the metal film are simultaneously laser processed. A well-known YAG laser is effective as a laser light source. By adjusting the output of this laser or the interval between output pulses, it is possible to etch the thin film to any desired depth. However, in this case, as shown in FIG.
2 remains, and the separation of the power generation regions becomes incomplete. Therefore,
Metal electrodes 41 and 42 completely separated in the steps up to this point
．． 43 as a mask, the crystallized silicon layer 91.
Etch 92. The method is to introduce a mixed gas of O-rich and CF into a vacuum chamber and expose it to a high-frequency glow of several hundred W for about 1 minute, which removes it almost completely as shown in Figure 1 (C1). Another method is to use 2% sodium hydroxide at a temperature of 50°C.
It can be similarly removed by immersion in an aqueous solution (at 50° C.) for about 5 minutes. In this case, the separation groove 81
．． Although the amorphous silicon layers 34 and 35 remain separated on the left side of the figure 82, there is no problem because the amorphous silicon layer in this region does not originally contribute to power generation.

【Effect of the invention】

The present invention uses laser processing not only to separate transparent electrodes and semiconductor active layers, but also to separate and form metal electrodes.
In this case, the underlying semiconductor thin film is also removed, and the remaining semiconductor layer affected by the laser beam is plasma etched or chemically etched using the metal electrode formed afterwards as a mask, completely removing the power generation area. can be separated, and short circuits between adjacent metal electrodes do not occur. As a result, precision machining using a laser can be applied to separate each layer, and the effective area ratio increases to 95% or more. Note that although the above description has been made by taking as an example a semiconductor active layer having an amorphous silicon p-1-n structure and a metal electrode made of aluminum, it goes without saying that the present invention is not limited to this.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional view showing an embodiment of the present invention in the order of steps, Fig. 2 is a partial cross-sectional view of a solar cell made by the mask method or photoetching method, and Fig. 3 is a partial cross-sectional view of a solar cell made by the conventional laser processing method. FIG. 3 is a partial cross-sectional view sequentially showing the steps in the case of FIG. 1; Glass substrate, 21.22, 23: Transparent electrode, 31
．． 32°33: Amorphous silicon layer, 4: Metal film, 41.
42, 43: metal electrode, 81, 82: layer separation groove, 91.
92: Residual silicon layer. +J: nnn7-;': For uranguchi\-Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1) A transparent conductive film, a semiconductor thin film, and a metal film are deposited on the entire surface of the transparent insulating substrate, and then separated and laminated. At this time, the position of each separated portion is sequentially shifted to form a transparent electrode, a semiconductor active layer, and a metal film. When forming a plurality of power generation regions consisting of electrodes connected in series, the metal film deposited on the entire surface of the transparent electrode and the semiconductor active layer is separated by laser light and the metal electrodes are formed. 1. A method for manufacturing a thin film solar cell, which comprises forming a semiconductor thin film, removing most of the underlying semiconductor thin film, and further removing the remaining semiconductor thin film by plasma etching or chemical etching using a metal electrode as a mask.