JPS59211290A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a GaAs solar battery durable against severe temperature environment by forming a solder layer inside the end face in the prescribed size on the electrode surface formed with a GaAs layer, thereby reducing the thermal stress of the electrode and the solder layer to the GaAs layer. CONSTITUTION:In the electrode surfaces of P-side electrode 6 and N-side electrode 7, a solder layer 8' is formed on the electrode surface intruded by 50mum or longer inside from the outer periphery of the electrode surface. The thickness of the layer 8' is, for example, 30-50mum. Even if a GaAs solar battery 20 thus obtained has thickly 30-50mum of thickness of the layer 8', the end face of the layer 8' is disposed inside the prescribed size from the end face of the P-side electrode 6. Accordingly, the thermal stress applied to the P type GaAs layer 2 of the solder layer 8' can be alleviated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrode structure of a semiconductor element, and particularly to a semiconductor device in which thermal stress thereof is reduced.

FIG. 1 is a plan view showing an example of a conventional GaAs solar cell;
FIG. 2 is a sectional view taken along the line fl-1 in FIG. In these figures, a conventional GaAs solar cell 10 is shown.

A p-type GaAs layer 2v is formed on an n-type GaAs substrate 1,
A pn junction 3 is formed between the two, and a p-type Ga
A p-type (AlGa) As layer 4 is formed on the Aa layer 2. The n-side electrode T is formed on the back surface of the n-type GaAs substrate 1, and the p-side electrode 6.9 is partially formed on the surface of the p-type GaAs layer 2 so as not to significantly impede light incidence on the same surface. ing. An antireflection film 5 is formed on the portion where the P-side electrodes 6 and 9 are not formed. Furthermore, in order to facilitate connection with an external lead, the p-side electrode 6. A solder layer 8 is formed on the surface of the n-side electrode 7. The main electrode material of the p-side electrode 6 and the n-side electrode 7 is Ag, and its thickness is several μm, and the thickness of the solder layer 8 is 30 to 50 μm.

Since the conventional GaAs solar cell 10 is configured as described above, when a thermal cycle test is performed, GaA
Due to the differences in the thermal expansion coefficients of the s-crystal, the electrode material (Ag in this example), and the solder, a large stress is applied to the interface between the p-type GaAs layer 2 and the p-side electrode 6.9, causing the p-side electrode 6.9 to There are drawbacks such as peeling at the interface of the p-type GaAs layer 2 or cracking of the p-type GaAs layer 2.

Particularly in recent years, solar cells have been widely used as a power source for space equipment such as artificial satellites, and in this space environment, unlike on the ground, solar cells are subject to large thermal cycles.In general, the low temperature is -140℃ to -190℃, At high temperatures: +120℃~
It is said to be +150℃. Therefore, in order to reduce the thermal stress as much as possible, it is necessary to reduce the thickness of the solder layer 8. However, if the solder layer 8 is made thinner, the tensile strength of the soldered external leads decreases.

This invention was made in order to eliminate the drawbacks of the conventional methods as described above, and by forming a solder layer on the inside of the electrode surface formed on the GaAs layer, the solder layer is formed on the GaAs layer. The purpose of this invention is to provide a GaAs solar cell that can withstand harsh temperature environments by reducing thermal stress on electrodes and solder layers. The present invention will be explained below with reference to the drawings.

3 and 4 show an embodiment of the present invention, with FIG. 3 being a plan view and FIG. 4 being a sectional view taken along the mV-mV line in FIG. 3. In these figures, 20 is a GaA according to the present invention.
The difference between this solar cell and the conventional example shown in FIGS. 1 and 2 lies in the formation of the solder layer 8', and the rest is the same as the conventional example.

That is, the p-side electrode 6. On each electrode surface of the n-side electrode T, 50 mm inward from the outer periphery of each electrode surface.
A solder layer 8' is formed on the electrode surface with a depth of .mu.m or more. The thickness of the solder layer 8' is 30 μm to 50 μm. The antireflection film 5 is made of Si3N and has a thickness of approximately 750 mm.

As described above, the GaAs solar cell 20 according to the present invention is significantly different from conventional GaAs solar cells in terms of electrode structure.

The GaAs+ solar cell 20 obtained in this way has a thickness of 30 μm to 50 μm, but the end surface of the solder layer 8′ is located inside the end surface of the p-side electrode 6 by the required dimension. , p-type GaAs layer 2 of 'solder layer 8'
The thermal stress applied to is reduced. Table 1 shows the GaAs solar cell 10 having a conventional structure and the GaAs solar cell 10 according to the present invention.
The thermal shock test results of the solar cell 20 are compared.

The test conditions were to store at -196°C for 10 minutes, then store at +196°C for 10 minutes.
1 heat cycle of heating to 140℃ and storing for 10 minutes
Repeated 0 cycles.

Table 1 Thermal Shock Test Results As mentioned above, the GaAs solar cell 20 according to the present invention has 0 failures even under the difficult test conditions of -196°C on the low temperature side and +140°C on the high temperature side, and the solder layer 8' The effect of reducing the thermal stress on the p-type GaAs+ layer 2 is sufficiently seen.

In the above embodiments, a solar cell using GaA 11 Y has been described, but the present invention can also be applied to solar cells using other semiconductors and semiconductor devices other than solar cells.

As explained in detail above, in the present invention, the solder layer is formed on the electrode surface so as to be within the required dimension from the end face of the solder layer, so the thermal stress applied to the semiconductor crystal of the solder layer is greatly reduced, and Thermal cycle environment (e.g. space environment)
However, it has the effect of providing high reliability.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an example of a conventional GaAs solar cell;
Figure 2 is a sectional view taken along line T in Figure 1, Figures 3 and 4.
The figures are a plan view and a cross-sectional view taken along -rvm of a GaA3 solar cell showing an embodiment of the present invention. In the figure, 1 is an n-type GaAs substrate, 2 is a p-type GaAs layer, 3
is a pn junction, 6 and 9 are p-side electrodes, T is an n-side electrode, 8' is a solder layer, and 20 is a GaAs solar cell. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Fig. 1 8 Fig. 2 Fig. 3 Fig. 4 Mr. Commissioner of the Japan Patent Office 1, Indication of the case Patent Application No. 1981-813845 2,
Title of the invention: Semiconductor device 3, Relationship with the person making the amendment: Hitoshi Katayama, representative of the patent applicant, Section 5, Detailed explanation of the invention in the specification to be amended, column 6, Specification of contents of the amendment, page 2, 16 "P-side electrode 69" in rows 17 and 17 are respectively corrected to "rP-side electrode 6". that's all

Claims (2)

[Claims] (1) A semiconductor device characterized in that, in an electrode surface formed on a semiconductor surface, a solder layer is formed on the electrode surface from the end surface by a predetermined distance inward. (2) The semiconductor device according to claim (1), characterized in that gallium arsenide is used as the semiconductor and silver is used as the electrode.