JPH08250634A - Manufacture of diode provided with interconnector - Google Patents

Abstract

PURPOSE: To simplify a manufacturing process and improve insulation reliability, by forming a through hole in one end portion of a diode forming part by etching or with a laser cutter, and surface-treating the surface of the through hole with an etching solution. CONSTITUTION: A through hole 22 is formed in one end portion of the diode forming part of a semiconductor substrate 21 by etching or with a laser cutter. The surface of the through hole 22 is subjected to surface treatment by second etching using a mixed solution of hydrofluoric acid and nitric acid. Thereby an oxide film and an insulating film are simultaneously formed on the diode surface and the through hole surface, so that the working process is simplified and the working time can be reduced. By the surface treatment of the through hole 21, double insulating structure constituted of the oxide film and the insulating film is obtained on the diode side surface in the interconnector leading-out direction, so that insulation reliability can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell, in particular, a solar cell used as a power source for an artificial satellite or a space station operating in outer space, which is used as a blocking diode or a bypass diode for protecting the solar cell. The present invention relates to a method of manufacturing a diode with a connector.

[0002]

2. Description of the Related Art In artificial satellites and space stations that operate in outer space, a so-called solar cell panel is used as a power source, in which a plurality of solar cells are connected in parallel and pasted on the panel. The demand for electric power is increasing with the increase in functionality and size of artificial satellites, and accordingly, there is a demand for size increase of solar cell panels. However, since there is a limit to the capacity and launch weight of the launch vehicle of the artificial satellite, it is desirable that the solar cell panel be small and lightweight when launched. Diodes are connected to the solar cell panel to protect the solar cell.

Conventionally, this diode is attached to the back of a solar cell panel or the main body of an artificial satellite. As solar panels have grown in size, satellites have been launched with the solar panels folded and deployed in outer space.The panels themselves have become thinner and smaller, and the diodes themselves have become solar cells. The same thickness has been developed.

In this thin diode, a semiconductor substrate is used as a substrate of the diode, one electrode of which is provided with metal on the back surface of the semiconductor substrate, and the other electrode is formed by drawing a metal foil as a terminal (interconnector). There is.

FIG. 10 is a longitudinal sectional view showing an example of a conventional thin diode with an interconnector.

Reference numeral 1 denotes, for example, a P-type or N-type semiconductor substrate, which has a size of 2 cm × 2 cm and a thickness of 0.1 to 0.5.
Made of mm single crystal silicon. There is also a case where the size of one side of the semiconductor substrate 1 is about 1 cm to 10 cm.

On the surface of the semiconductor substrate 1, a diffusion layer 3 of a conductivity type opposite to the impurities of the substrate 1 is formed, and the semiconductor substrate 1
A PN junction portion 9 is formed between and and functions as a diode. The surface of the semiconductor substrate 1 is covered with an oxide film 2 such as SiO ₂ . The electrode 4 of the N-type diffusion layer 3 is formed by forming a hole in the oxide film 2 and vapor-depositing a metal. One end of a metal foil 6 is attached to the electrode 4 by welding or soldering and is drawn out as a terminal. There is. The metal foil 6 is
It is used to connect adjacent diodes and solar cells. A metal coating is provided on the back surface of the semiconductor substrate 1 to form the electrodes 5.

On these surfaces, in order to improve heat dissipation in outer space and to prevent sunlight from entering the semiconductor substrate 1, the leakage current in the reverse direction of the diode due to the photocurrent is reduced. Reflective layer 8 made of aluminum plate or mirror
Are attached by an adhesive 7. The semiconductor substrate 1 and the metal foil 6 are insulated by the oxide film 2 and the adhesive 7.

It is necessary to insulate the semiconductor substrate 1 and the metal foil 6, and if the insulation between them is broken, it will not function as a diode. Therefore, it has been considered that the semiconductor substrate 1 is subjected to mesa etching in order to strengthen the insulation to improve the insulation of the portion where the metal foil 6 is in contact with the semiconductor substrate 1.

FIG. 11 is a vertical sectional view of an example of the above,
A mesa portion 10 is provided on the side of the semiconductor substrate 1 below the metal foil 6 by mesa etching. The mesa portion 10 increases the distance between the metal foil 6 and the semiconductor substrate 1 and strengthens the insulation.

However, in the case of this structure, dust or the like may be attached between the semiconductor substrate 1 and the metal foil 6 to cause conduction.

As a means for solving the above problem, Japanese Patent Laid-Open No. Hei 6 (1994)
There is a diode with an interconnector described in Japanese Patent No. 53377. FIG. 12 is a vertical sectional view of the example.

In the diode with interconnector, at least the side surface of the semiconductor substrate 1 below the metal foil 6 is covered with the insulating film 1.
It is covered with 1. This side surface insulating film 11 is
For example, an insulating film formed by applying a heat treatment on a side surface of a solution of a silicon oxide film dissolved in a solvent, or a polyimide film formed by applying a heat treatment by applying a polyimide varnish,
A powder glass is electro-fused and a glass layer or the like formed by heat treatment is formed into a single layer or multiple layers.

In FIG. 12, the mesa portion 10 is formed by mesa etching, but since the insulating film 11 is provided, the insulating effect of the side surface portion is enhanced without the mesa portion 10. Of course, the insulation is further strengthened by using the mesa portion 10 together. As a method of forming the side surface insulating film 11 with a uniform thickness, for example, a material of the insulating film to be applied in advance is spin-coated on a plate having a flat surface, the material is spread to a uniform thickness, and the side surface insulating film 11 is formed on the plate. By erecting the semiconductor substrate 1 of the diode, the material can be transferred to the side surface.

Further, as shown in FIG. 13, there is also one in which an insulating layer 12 is formed on the surface of the electrode 4 and the oxide film 2 excluding the joint between the metal foil 6 and the electrode 4. In the figure, (a) is a plan view and (b) is a longitudinal sectional view.

The insulating layer 12 is intended to enhance the insulation between the surface of the semiconductor substrate 1 and the metal foil 6. The insulating layer 12
Otherwise, the oxide film 2 is formed by photo-etching, and thus the pinholes generated during the formation of the oxide film may deteriorate the insulation between the surface of the semiconductor substrate 1 and the metal foil 6.

[0017]

However, the manufacturing method of the diode with interconnector shown in FIG.
As shown in FIG. 3, a pattern of a plurality of diodes is formed on a circular wafer, and in the wafer state, a mesa portion forming step of each diode, an oxide film forming step, a diffusion step, an electrode forming step, an upper surface insulating film forming step. Are sequentially performed, and then each diode is cut by a dicing saw or the like. In the mesa portion forming step, the mesa portion 10 is formed by etching to a predetermined depth with a mixed solution of hydrofluoric acid and nitric acid. In the figure, 13 is a dicing line.

Thereafter, as described above, for example, the material of the insulating film to be applied in advance is spin-coated on a plate having a flat surface, the material is spread to a uniform thickness, and the semiconductor substrate of the diode is formed thereon. By setting 1, the material is transferred to the side surface and the side surface insulating layer 11 is formed.

Therefore, the side surface insulating layer 11 and the insulating layer 1 are
2 cannot be formed at the same time, and the side insulating layer 11 is formed for each individual diode, resulting in an extremely long working time and a variation in adhesion strength.

Further, since the oxide film 2 is not formed on the side surface portion of the semiconductor substrate, the side surface portion is to be insulated only by the side surface insulating film 11, and when the adhesion strength of the side surface insulating film 11 is weak. Had a problem that the side surface insulating film 11 peeled off and lost its function.

In view of the above problems, it is an object of the present invention to provide a method of manufacturing a diode with an interconnector, which simplifies the manufacturing process and improves the insulation reliability.

[0022]

According to a first aspect of the present invention, there is provided a method of manufacturing a diode with an interconnector, comprising: a diode; and an interconnector electrically connecting the diode and a semiconductor element in a series direction or a parallel direction. In the method for manufacturing a diode with an interconnector, wherein the interconnector is drawn out from one electrode part of the diode to one end side of the diode in a substantially parallel manner, each diode is formed on a semiconductor substrate in which a plurality of diodes are formed. Forming a through hole at one end of the portion, and forming a diode by providing a diffusion portion by diffusing an impurity of a conductivity type opposite to that of the semiconductor substrate at a predetermined position of each diode forming portion, A step of simultaneously forming an oxide film on the upper surface of the diode and the surface of the through hole excluding the electrode forming portion of the diffusion portion, and the diffusion portion surface. And a step of simultaneously forming an insulating film on the surface of the electrode and the surface of the oxide film excluding the connecting portion of the electrode with the interconnector. Is.

In the method of manufacturing a diode with an interconnector according to a second aspect of the present invention, the step of forming the through hole comprises:
A step of coating a portion of the semiconductor substrate excluding the through hole forming portion with a resist, a step of etching the through hole forming portion with an etching solution, and a step of removing the resist. To do.

In the method of manufacturing a diode with an interconnector according to a third aspect of the present invention, the step of forming the through hole includes
A through hole is formed by a laser cutter in the through hole forming portion of the semiconductor substrate.

[0025]

According to the above structure, the method for manufacturing a diode with an interconnector according to the present invention has a structure in which a through hole is formed at one end of the diode forming portion by etching or a laser cutter. Further, it becomes possible to simultaneously form an oxide film and an insulating film, which simplifies the working process and shortens the working time. Also,
The surface of the through-hole, that is, the side surface of the diode in the direction of drawing out the interconnector, has a double insulating structure composed of an oxide film and an insulating film, so that insulation reliability can be improved.

[0026]

FIG. 1 is a manufacturing process diagram showing a method of manufacturing a diode with an interconnector according to an embodiment of the present invention, wherein (a) to (e) are plan views and (f) to (j). ) Is a partial vertical sectional view. Note that (f) to (j) correspond to the above (a) to (e), and a single diode is illustrated. FIG. 2 is a manufacturing process diagram showing the through hole forming process shown in FIGS. 3A and 3B are configuration diagrams of a diode with an interconnector formed by the manufacturing method, FIG. 3A is a plan view, and FIG. 3B is a vertical sectional view.

In the method of manufacturing the diode with interconnector, as shown in FIGS. 1A and 1F, first, at one end of each diode forming portion of the semiconductor substrate 21 in which a plurality of diodes are formed, Through-hole 22 which is shared with the adjacent diode formation portion and whose surface is treated with an etching solution
To form. As a result, the mesa portion 23 is formed at one end of each diode formation portion. The semiconductor substrate 21 is made of, for example, a silicon wafer.

Next, as shown in FIGS. 1 (b) and 1 (g),
An impurity having a conductivity type opposite to that of the semiconductor substrate 21 is diffused at a predetermined position on the surface of each diode formation portion to form a diffusion portion 24, and a PN junction is formed between the diffusion portion 24 and the semiconductor substrate 21. The portion 25 is formed to form a diode, and an oxide film (for example, SiO ₂ ) 26 is formed on the diode upper surface and the surface of the through hole 22 except a part of the diffusion portion 24.
Are simultaneously formed in one step.

Next, as shown in FIGS. 1 (c) and 1 (h),
A metal is deposited on the surface of the diffusion portion 24 where the oxide film 26 is not formed and the rear surface of the semiconductor substrate 21 to deposit the surface electrode portion 27,
The back electrode portion 28 is formed.

Next, as shown in FIGS. 1 (d) and 1 (i),
An insulating film 29 is formed on the surface of the electrode portion and the surface of the oxide film 26 excluding a part of the surface electrode portion 27 (the connection portion with the metal foil).
Formed simultaneously in the process. Next, as shown in FIGS. 1E and 1J, a plurality of wafer diodes connected along the dicing line 30 are divided into individual diodes.

After that, as shown in FIG. 3, one end of a metal foil 31 (interconnector) is attached to the surface electrode portion 27 by welding or soldering, and these surfaces are bonded with an adhesive 32 between them. It is covered with a reflection plate 33. The metal foil 31 is drawn out to one end side of the semiconductor substrate 21.

The step of forming the through hole 22 will be described in detail with reference to FIG. 2. First, as shown in 2 (a), the through hole forming portion on the surface of the semiconductor substrate 21 on which a plurality of diodes are formed. A portion other than (a boundary portion between the diode forming portions) and the back surface of the semiconductor substrate 21 are covered with a photoresist 34. It is desirable that the pattern of the photoresist 34 has a width larger than that of the dicing blade in order to shorten a first etching time described later. This is because if the width is smaller than the width of the dicing blade, it is necessary to perform extra etching by the difference between the width of the dicing blade and the width of the pattern.

Next, as shown in FIG. 2B, the first etching is performed with a mixed solution of hydrofluoric acid and nitric acid. In the case of a silicon substrate, the etching time is about 50
%): Nitric acid (concentration 60%) = 1:10 when mixed at a ratio of about 10 μm for 1 minute, so that when a semiconductor substrate of 100 μm is used, it takes about 10 minutes.
The width of the upper surface of the through-hole 22 is the width of the pattern plus 200 μm in the lateral direction.

Thereafter, as shown in FIG. 2C, the photoresist is peeled off to form a mesa portion 23 '. Subsequently, by performing a second etching for about 1 minute with a mixed solution of hydrofluoric acid (concentration 50%): nitric acid (concentration 60%) = 1:10, the mesa portion 23 is removed as shown in FIG. 2D. It is formed.

FIG. 4 is a manufacturing process diagram showing a method of manufacturing a diode with an interconnector according to another embodiment of the present invention. FIG. 5 is a vertical sectional view of a diode with an interconnector manufactured by the manufacturing method. For this example,
Only points different from the above embodiment will be described.

The method of manufacturing the diode with an interconnector differs from the above embodiment in the method of forming the mesa portion 23a, that is, the method of forming the through hole 22a.

In this embodiment, anisotropic etching with alkali is utilized. First, as shown in FIG. 4A, the front and back surfaces of the semiconductor substrate 21a are oxidized to form an oxide film 35, Oxide film 3 on the surface side of the semiconductor substrate 21a
A predetermined pattern is formed on the surface of the oxide film 35 by the photoresist 36 to partially etch the oxide film 35,
As shown in (b), the photoresist 36 is peeled off. In the case of a thermal oxide film, the thickness of the oxide film 35 needs to be about 1/100 of the thickness of the semiconductor substrate 21a.

Next, 4 l of pure water, 70 g of potassium hydroxide,
After etching with a mixed solution of 150 cc of isopropyl alcohol at about 70 ° C., the oxide film 35 is etched with hydrofluoric acid or the like. As a result, the shape shown in FIG. 4C is obtained, and the mesa portion 23a 'is obtained.

Thereafter, as shown in FIG. 4D, the second etching is performed for about 1 minute with a mixed solution of hydrofluoric acid (concentration 50%): nitric acid (concentration 60%) = 1:10. The mesa portion 23a is formed.

FIG. 6 is a manufacturing process chart showing a manufacturing method of a diode with an interconnector according to still another embodiment of the present invention. FIG. 7 is a longitudinal sectional view of a diode with an interconnector manufactured by the manufacturing method. This embodiment will be described only on the points different from the embodiment shown in FIGS.

In the method of manufacturing the diode with interconnector, a through hole 22b is formed in the through hole forming portion of the semiconductor substrate 21b by using a laser cutter. First, as shown in FIG. 6 (a), A through hole 22b is formed in the through hole forming portion with a laser cutter. Next, FIG.
As shown in (b), the surface of the through-hole 22b is subjected to surface treatment by second etching with a mixed solution of hydrofluoric acid and nitric acid for about 1 to 2 minutes. The width of the through hole 22b is larger than the width of the dicing blade. In the figure, 23b is a mesa portion.

FIG. 7 shows the structure of a diode with an interconnector using the semiconductor substrate 21b having such a through hole 22b.

FIG. 8 is a manufacturing process diagram showing a manufacturing method of a diode with an interconnector according to still another embodiment of the present invention. FIG. 9 is a vertical cross-sectional view of a diode with an interconnector made by the manufacturing method. This embodiment will be described only on the points different from the embodiment shown in FIGS.

In the method of manufacturing the diode with interconnector, the through hole 22c is formed in the through hole forming portion of the semiconductor substrate 21c by etching and using a laser cutter. First, as shown in FIG. Then, a portion of the surface of the semiconductor substrate 21c excluding the through hole forming portion is covered with the photoresist 37. The opening width of the photoresist 37 is, for example, larger than the width of the dicing blade.

Next, as shown in FIG. 8B, the first etching is performed with a mixed solution of hydrofluoric acid and nitric acid up to the middle of the semiconductor substrate 21b. Subsequently, as shown in FIG. 8C, the photoresist 37 is removed. The etching time of the first etching is, eg, about 2 minutes.

Thereafter, as shown in FIG. 8D, a through hole 22c is formed in the etched through hole forming portion by a laser cutter. Next, as shown in FIG.
The surface of the through hole 22c is subjected to surface treatment by second etching with a mixed solution of hydrofluoric acid and nitric acid. The etching time of the second etching is about 1 minute. 23 in the figure
c is a mesa part.

FIG. 9 shows the structure of a diode with an interconnector using the semiconductor substrate 21c having such a through hole 22c.

As described above, in the method of manufacturing the diode with an interconnector according to the above-described embodiment, the through holes 22, 22a, 22b, 22c are formed at one end of the diode forming portion by etching and / or a laser cutter. Therefore, it becomes possible to simultaneously form the oxide film 26 and the insulating film 29 on the surface of the diode and the surface of the through hole, which simplifies the working process and shortens the working time.

Further, through holes 22, 22a, 22b, 22
The surface c, that is, the side surface of the diode in the drawing direction of the metal foil (interconnector) 31, is the oxide film 26 and the insulating film 2.
The double insulation structure of 9 can be obtained, and the insulation reliability can be improved.

Further, the through holes 22, 22a, 22b, 2
By sharing 2c between the adjacent diode forming portions, the manufacturing process can be simplified. For example, the pattern formation of the photoresists 34, 36, 37 is easy. Also, the through holes 22b, 22 formed by the laser cutter
The formation of c is reduced by half.

[0051]

As described above, according to the method for manufacturing a diode with an interconnector of the present invention, a through hole is formed at one end of the diode forming portion by etching or a laser cutter, and the surface of the through hole is formed. Since the surface treatment is performed with an etching solution, an oxide film and an insulating film can be formed on the diode surface and the through hole surface at the same time, which simplifies the working process and shortens the working time.

Further, the surface of the through-hole, that is, the side surface of the diode in the direction of drawing out the interconnector, has a double insulating structure of an oxide film and an insulating film, and the insulation reliability is improved.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of a diode with an interconnector according to an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram showing a through-hole forming process shown in FIG.

FIG. 3 is a configuration diagram of a diode with an interconnector manufactured by the manufacturing method shown in FIG. 1, in which (a) is a plan view,
(B) is a longitudinal sectional view.

FIG. 4 is a manufacturing process diagram of a diode with an interconnector according to another embodiment of the present invention.

5 is a vertical cross-sectional view of a diode with an interconnector manufactured by the manufacturing method shown in FIG.

FIG. 6 is a manufacturing process diagram of a diode with an interconnector according to still another embodiment of the present invention.

7 is a vertical cross-sectional view of a diode with an interconnector manufactured by the manufacturing method shown in FIG.

FIG. 8 is a manufacturing process diagram of a diode with an interconnector according to still another embodiment of the present invention.

9 is a vertical sectional view of a diode with an interconnector manufactured by the manufacturing method shown in FIG.

FIG. 10 is a vertical sectional view showing the structure of a conventional diode with an interconnector.

FIG. 11 is a vertical cross-sectional view showing the structure of another conventional diode with an interconnector.

FIG. 12 is a vertical cross-sectional view showing the structure of still another conventional diode with an interconnector.

13A is a plan view and FIG. 13B is a longitudinal sectional view showing the structure of still another conventional diode with an interconnector.

FIG. 14 is a plan view for explaining the method for manufacturing the conventional diode with an interconnector shown in FIG.

[Explanation of symbols]

 21, 21a, 21b, 21c Semiconductor substrate 22, 22a, 22b, 22c Through hole 24 Diffusion part 26 Oxide film 27 Surface electrode part 29 Insulation film 31 Metal foil (interconnector)

Claims (3)

[Claims] 1. A diode and an interconnector for electrically connecting the diode and the semiconductor element in a series direction or a parallel direction, the interconnector being substantially connected from one electrode portion of the diode to one end side of the diode. In a method of manufacturing a diode with an interconnector that is drawn out in parallel, a step of forming a through hole at one end of each diode formation portion of a semiconductor substrate on which a plurality of diodes are formed, and a predetermined diode formation portion of each diode formation portion. Forming a diode by diffusing an impurity of a conductivity type opposite to that of the semiconductor substrate at a position to form a diffusion portion, and forming an oxide film on the diode upper surface and the through hole surface at the same time except the electrode forming portion of the diffusion portion. And a step of forming an electrode part on the surface of the diffusion part, and a part of connecting the electrode part with the interconnector is excluded. Method for producing a diode with interconnectors, characterized by comprising a step of forming a pole surface and the insulating film on the oxide film surface at the same time. 2. The step of forming the through hole comprises: covering the portion of the semiconductor substrate except the through hole forming portion with a resist; etching the through hole forming portion with an etching solution; The method for manufacturing a diode with an interconnector according to claim 1, further comprising: 3. The method of manufacturing a diode with an interconnector according to claim 1, wherein in the step of forming the through hole, the through hole is formed by a laser cutter in a through hole forming portion of the semiconductor substrate. .