JP3261278B2 - Manufacturing method of diode with interconnector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell, particularly 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 for manufacturing a diode with a connector.

[0002]

2. Description of the Related Art In artificial satellites and space stations operating 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 attached on a panel. The demand for electric power is increasing with the enhancement of functions and the size of artificial satellites, and accordingly, the size of solar cell panels is required to be increased. However, since the capacity and launch weight of the launch vehicle of an artificial satellite are limited, it is desired that the solar cell panel be small and lightweight when launched. A diode is connected to the solar cell panel to protect the solar cell.

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and deployed in outer space, and the panels themselves have become thinner and smaller, and the diodes themselves have been replaced by solar cells.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

In this thin-type diode, a semiconductor substrate is used as a substrate of the diode. One electrode is provided with a metal on the back surface of the semiconductor substrate, and the other electrode is formed by drawing a metal foil as a terminal (interconnector). I have.

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

Reference numeral 1 denotes, for example, a P-type or N-type semiconductor substrate having a size of 2 cm × 2 cm and a thickness of 0.1 to 0.5.
mm of silicon single crystal. In some cases, 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 impurity of the substrate 1 is formed.
A PN junction 9 is formed between the two 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 depositing a metal. One end of a metal foil 6 is attached to the electrode 4 by welding or soldering, and is pulled out as a terminal. I have. The metal foil 6
Used to connect adjacent diodes and solar cells. A metal film is provided on the back surface of the semiconductor substrate 1, and an electrode 5 is formed.

On these surfaces, in order to improve heat radiation in outer space and to reduce the leakage current of the diode due to photocurrent in the reverse direction by preventing sunlight from entering the semiconductor substrate 1, 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.

The semiconductor substrate 1 and the metal foil 6 need to be insulated, and if the insulation between them is broken, they will not function as a diode. For this reason, it has been considered that the semiconductor substrate 1 is subjected to mesa etching in order to strengthen the insulation, thereby improving the insulation at a portion where the metal foil 6 contacts the semiconductor substrate 1.

FIG. 11 is a vertical cross-sectional view of one example.
A mesa portion 10 is provided by performing mesa etching on the side of the semiconductor substrate 1 below the metal foil 6. Due to the mesa portion 10, the distance between the metal foil 6 and the semiconductor substrate 1 is increased, and the insulation is strengthened.

However, in the case of this structure, there is a possibility that dust or the like adheres between the semiconductor substrate 1 and the metal foil 6 and conducts.

As a solution to the problem, Japanese Patent Laid-Open No.
There is a diode with an interconnector described in JP-A-53377. FIG. 12 is a longitudinal sectional view of one example.

In the diode with an interconnector, at least the side surface of the semiconductor substrate 1 below the metal foil 6 has an insulating film 1
It is covered with 1. This side insulating film 11
For example, an insulating film formed by applying a heat treatment to a side obtained by dissolving a silicon oxide film in a solvent and a polyimide film formed by applying a polyimide varnish and applying a heat treatment,
A single glass or multiple layers of a glass layer or the like formed by heat-treating a glass powder by electrofusion are used.

In FIG. 12, the mesa portion 10 is formed by mesa etching. However, since the insulating film 11 is provided, the insulating effect on the side surface portion is enhanced without the mesa portion 10. Needless to say, the use of the mesa unit 10 further enhances the insulation. As a method of forming the side surface insulating film 11 with a uniform thickness, for example, a material for the insulating film to be applied in advance is spin-coated on a plate having a flat surface, and the material is stretched to a uniform thickness. 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 a structure in which an insulating layer 12 is formed on the surface of the electrode 4 and the oxide film 2 except for 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 enhances the insulation between the surface of the semiconductor substrate 1 and the metal foil 6. The insulating layer 12
Otherwise, since the oxide film 2 is formed by photoetching, the insulating property between the surface of the semiconductor substrate 1 and the metal foil 6 may be deteriorated due to pinholes generated during the formation of the oxide film.

[0017]

However, the method for manufacturing the diode with the interconnector shown in FIG.
As shown in the figure, a pattern of a plurality of diodes is formed on a circular wafer, and a mesa portion forming step, an oxide film forming step, a diffusion step, an electrode forming step, and an upper surface insulating film forming step of each diode are performed in the wafer state. Are sequentially performed, and thereafter, the individual diodes are 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, reference numeral 13 denotes 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, and the material is stretched to a uniform thickness. By setting 1, the material is transferred to the side surface, and the side surface insulating layer 11 is formed.

Therefore, the side insulating layer 11 and the insulating layer 1
2 cannot be formed at the same time, and the work time is very long because the side surface insulating layer 11 is formed for each individual diode, and the adhesion strength tends to vary.

Also, since the oxide film 2 is not formed on the side surface of the semiconductor substrate, the side surface 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. There was a problem that the side insulating film 11 was peeled off and lost its function.

The present invention has been made in view of the above problems, and has as its object to provide a method of manufacturing a diode with an interconnector which can simplify a manufacturing process and improve 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 for electrically connecting the diode and a semiconductor element in a serial or parallel direction. A method for manufacturing a diode with an interconnector, wherein the interconnector is pulled out substantially in parallel to one end of the diode from one electrode portion of the diode, wherein each diode is formed on a semiconductor substrate on 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 the opposite conductivity type to the impurity of the semiconductor substrate at a predetermined position of each of the diode formation portions; 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; Forming an electrode portion, and simultaneously forming an insulating film on the surface of the electrode portion and the surface of the oxide film excluding the connection portion of the electrode portion with the interconnector. It is.

According to a second aspect of the present invention, in the method of manufacturing a diode with an interconnector, the step of forming the through hole includes the following steps:
A step of coating a portion of the semiconductor substrate other than the through-hole forming portion with a resist, a step of etching the through-hole forming portion with an etchant, and a step of removing the resist. Is what you do.

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

[0025]

According to the above construction, the method of 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 a diode forming portion by etching or a laser cutter. At the same time, the oxide film and the insulating film can be simultaneously formed, so that the operation steps can be simplified and the operation time can be reduced. Also,
The surface of the through-hole, that is, the side surface of the diode in the direction in which the interconnector is drawn out, has a double insulating structure of an oxide film and an insulating film, and the insulation reliability can be improved.

[0026]

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

First, as shown in FIGS. 1 (a) and 1 (f), a method of manufacturing the diode with an interconnector includes, at one end of each diode forming portion of a semiconductor substrate 21 on which a plurality of diodes are formed, Through-hole 22 which is shared with an adjacent diode forming portion and whose surface is surface-treated with an etching solution
To form Thereby, the mesa portion 23 is formed at one end of each diode forming portion. The semiconductor substrate 21 is made of, for example, a silicon wafer.

Next, as shown in FIGS. 1B and 1G,
At a predetermined position on the surface of each diode forming portion, a diffusion portion 24 is formed by diffusing an impurity of the conductivity type opposite to that of the semiconductor substrate 21, and a PN junction is formed between the diffusion portion 24 and the semiconductor substrate 21. A diode is formed by forming a portion 25, and an oxide film (for example, SiO ₂ ) 26 is formed on the upper surface of the diode except for a part of the diffusion portion 24 and the surface of the through hole 22.
Are simultaneously formed in one step.

Next, as shown in FIGS. 1C and 1H,
Metal is deposited on the surface of the diffusion portion 24 where the oxide film 26 is not formed and the back surface of the semiconductor substrate 21 to form a 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 except for a part of the surface electrode portion 27 (connection portion to the metal foil).
It is formed simultaneously in the process. Next, as shown in FIGS. 1E and 1J, a plurality of wafer-shaped diodes connected along the dicing line 30 are divided into individual diodes.

Thereafter, 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 further interposed with an adhesive 32 therebetween. It is covered with a reflection plate 33. The metal foil 31 is drawn to one end 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 FIG. 2A, a through hole forming portion on the surface of the semiconductor substrate 21 on which a plurality of diodes are formed. A portion excluding (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 be larger in width than 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, a first etching is performed using a mixed solution of hydrofluoric acid and nitric acid. The etching time for a silicon substrate is hydrofluoric acid (concentration 50
%): When mixed at a ratio of nitric acid (concentration of 60%) = 1:10, about 10 μm is etched in one minute. For example, 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 equal to the width of the pattern plus 200 μm in the horizontal direction.

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

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

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

In this embodiment, anisotropic etching with alkali is used. 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 semiconductor substrate 21a
5, a predetermined pattern is formed by a photoresist 36, and the oxide film 35 is partially etched.
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 and about 70 ° C., the oxide film 35 is etched with hydrofluoric acid or the like. Thereby, the shape as shown in FIG. 4C is obtained, and the mesa portion 23a 'is obtained.

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

FIG. 6 is a manufacturing process diagram showing a method for manufacturing 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 with respect to differences from the embodiment shown in FIGS.

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

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

FIG. 8 is a manufacturing process diagram showing a method for manufacturing a diode with an interconnector according to still another embodiment of the present invention. FIG. 9 is a longitudinal sectional view of a diode with an interconnector manufactured by the manufacturing method. This embodiment will be described only with respect to differences from the embodiment shown in FIGS.

In the method of manufacturing the diode with an interconnector, a through hole 22c is formed in the through hole forming portion of the semiconductor substrate 21c by using etching and 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 a 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 halfway through the semiconductor substrate 21b using a mixed solution of hydrofluoric acid and nitric acid. Subsequently, as shown in FIG. 8C, the photoresist 37 is removed. The etching time of the first etching is, for example, 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 a surface treatment by a second etching using a mixed solution of hydrofluoric acid and nitric acid. The etching time of the second etching is about 1 minute. In the figure, 23
c is a mesa unit.

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

As described above, the manufacturing method of the diode with the interconnector according to the above embodiment is such that 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 is 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, thereby simplifying the operation process and shortening the operation time.

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

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

[0051]

As described above, according to the method of manufacturing a diode with an interconnector of the present invention, a through hole is formed at one end of a diode forming portion by etching or a laser cutter, and the surface of the through hole is formed. Since the surface is treated with an etchant, an oxide film and an insulating film can be simultaneously formed on the surface of the diode and the surface of the through hole, so that the working process can be simplified and the working time can be shortened.

Further, a double insulating structure of an oxide film and an insulating film is obtained on the surface of the through hole, that is, on the side surface of the diode in the direction in which the interconnector is drawn out, and the insulation reliability is improved.

[Brief description of the 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. 1;

3A and 3B are configuration diagrams of a diode with an interconnector formed by the manufacturing method shown in FIG. 1; FIG. 3A 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 longitudinal sectional view of a diode with an interconnector formed by the manufacturing method shown in FIG. 4;

FIG. 6 is a manufacturing process diagram 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 formed by the manufacturing method shown in FIG. 6;

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 formed by the manufacturing method shown in FIG.

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

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

FIG. 12 is a longitudinal 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)

(57) [Claims] 1. A semiconductor device comprising: a diode; and an interconnector for electrically connecting the diode and the semiconductor element in a serial direction or a parallel direction, wherein the interconnector is connected from one electrode of the diode to one end of the diode. In a method of manufacturing a diode with an interconnector drawn out in parallel, a step of forming a through hole at one end of each diode forming portion of a semiconductor substrate on which a plurality of diodes are formed; Forming a diode by diffusing an impurity of the opposite conductivity type to the impurity of the semiconductor substrate at a position to form a diffusion portion; and simultaneously forming an oxide film on the diode upper surface and the through hole surface excluding the electrode formation portion of the diffusion portion. Excluding a step of forming an electrode portion on the surface of the diffusion portion; and removing a portion of the electrode portion connected to the interconnector. 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, the step of covering a portion of the semiconductor substrate other than the through-hole forming portion with a resist, the step of etching the through-hole forming portion with an etchant, and the step of: 2. The method for manufacturing a diode with an interconnector according to claim 1, further comprising the step of: 3. The method for manufacturing a diode with an interconnector according to claim 1, wherein in the step of forming the through hole, a through hole is formed in a through hole forming portion of the semiconductor substrate by using a laser cutter. .