JPS59115524A - Formation of electrode for semiconductor device - Google Patents

Abstract

PURPOSE:To enable to form an electrode and a lead wire at the same time by performing a simple process by a method wherein a thin metal wire group for electrode is placed on the surface of a semiconductor element and heat and pressure are applied. CONSTITUTION:An N type diffusion layer 11 is formed on a P type Si substrate 10 and, at the same time, a solar battery element 13 whereon the lower electrode 12 is formed is arranged between a base heater 14 and the upper heater 15 when the upper electrode forming process is performed in such a manner that the electrode 12 is facing downward. Then, a fine metal wire group 16 is placed on the surface of the element 13 in such a manner that it is covering the whole surface. The heater 15 is brought down in the direction shown by the arrow P in the diagram maintaining the positional relations as above-mentioned, and pressure is applied on the element 13. As a result, the contacted part of the element and the fine wire group 16 is heated up by the heaters 14 and 15, and the fine wire group 16 is electrically and mechanically connected to the surface of the element 13. According to this method, the electrode can be formed by performing a heating and pressurizing process only, and besides a lead wire can be formed simultaneously, thereby enabling to cut down the manufacturing time remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method of forming electrodes for semiconductor devices, and particularly to a method of forming electrodes suitable for manufacturing methods of solar cells.

<Prior Art> Conventionally, electrodes of solar cells have been formed by a vacuum evaporation method or a conductive paste printing method. However, the vacuum evaporation method is unsuitable for low prices and mass production in terms of time and cost, and also has the drawback of large losses of evaporated gold, so currently the printing method of conductive paste is the mainstream. It is becoming. FIG. 1 shows a typical conductive paste printing method. First, Al is placed on the bottom surface of the silicon wafer 1.
Print and bake paste 2 (step (8)). The dust 3 formed on the lower surface of the Al paste 2 is an oxide film formed during the firing step. Next, there is a step (B) in which the dust 3 is chemically or physically removed, and a step (C) in which Ag paste 4 is printed on the exposed paste 2 to enable soldering. ), drying and firing (step (D)). After going through the above steps, Ag paste 4-
The lead wire 5 is soldered to the wire 1- with solder 6 to complete the wiring connection (step (E)). As described above, the conventional electrode forming method using a conductive paste is advantageous in terms of time and cost compared to the vacuum evaporation method because it does not require a vacuum process, and also has the advantage that there is no wastage of materials.

However, this method involves printing and baking the paste.

Moreover, since a soldering process is required, there is a drawback that the process becomes complicated, and a sufficient cost reduction cannot be achieved.

<Objective of the Invention> An object of the present invention is to provide a method for forming electrodes of a semiconductor device, which allows forming electrodes and forming lead wires at the same time in extremely simple steps.

<Structure of the Invention> This invention provides electrode gold rr5 such as wire cloth (metal mesh) on the surface of a semiconductor element in which a PN junction is formed.
The method is characterized in that the group of fine metal wires is connected to the surface of the semiconductor element by placing and applying heat and pressure to the group of wires.

FIG. 2 is a diagram illustrating the electrode forming method of the present invention. .

An N-type diffusion layer 11 is formed on a P-type silicon substrate 10, and an AI? In the step of forming the upper electrode, the solar cell element 13 having the lower electrode 12 formed by printing paste has the lower electrode 12 placed between the base heater 14 and the upper heater 15 on the lower side as shown in the figure. It is placed as follows. Then, element 1 is placed on the surface of element 13.
A group of thin metal wires 16 is placed so as to cover the entire surface of the metal wires 3. While maintaining the above positional relationship, the upper heater 15 is lowered in the direction of arrow P, and the element 13 is pressed with a constant pressure. Then, the contact portion between the element 13 and the metal wire group 16 is heated by the heater 14.15, and by heating and pressurizing for a certain period of time, the metal wire group 16 is electrically and mechanically connected to the element 1.
Connect to the surface of 3. When sufficient ohmic contact is obtained, the heater 15 is pulled up in the direction opposite to the arrow P, thereby completing the formation of the upper electrode. In this case, the surface of the element 13 may be a bare silicon surface, or may be formed with an insulating thin film such as lintitanate glass (P"FG) or silicone glass (SG), Further, a transparent conductive thin film such as indium tin oxide (TTO) or SnO may be formed.

<Effects of the Invention> According to the present invention, electrodes can be easily formed by only heating and pressurizing processes, and lead wires are also formed at the same time, so electrode formation and soldering of lead wires for wiring can be performed separately. This eliminates the need for this process, significantly reducing manufacturing time. In addition, by reducing the number of processes, large-scale installation (Rti) is no longer required,
It has the advantage of drastically reducing indirect material costs such as electricity and gas, and electrodes can be formed in normal air without requiring a special atmosphere. Furthermore, since a group of thin metal wires is used, there is an advantage that there is no need to decide in advance where the lead wires are to be taken.

<Example 1> Jtff: O, (15 mm, line width 0.1 m+r+, open [
An expanded band metal 16a with a ratio of about 90% is used. No. 31m (C) shows a partially enlarged view of this expanded metal 16a. Next, the bonding depth is approximately 0' on the P-type silicon substrate 10, and 3. An element 13 is prepared in which an N-type diffusion layer 11 of um is formed and Ag paste is printed on a P-type substrate IO1 as a lower electrode. And this element 13
Place the N-type Ftll on top of the base heater 14 whose temperature is adjusted to about 300°C, and place the expanded metal 1
Layer 6a on top. Next, the temperature was adjusted to about 300 degrees Celsius, and the pressure applied to the element 13 was about 300 k
Pressurize for 1 minute at g/C+a. When the above steps are executed, the N-type layer 11 and expanded metal 1
6a, good ohmic contact was obtained, and the mechanical strength was also high. The current-voltage characteristics of this element were measured using an AMC air mass) 1 solar simulator and were found to be 0.
．． A fill factor of 70 was obtained.

<Example 2> Lintinate glass (PT) was deposited on the P-type silicon substrate 10.
G) solution was applied and heat treated at 920° C. for 20 minutes to simultaneously form an N intermediate layer with a junction depth of about 0.3 μm and PTGl*17 as an antireflection film (see FIG. 4). P
The TG film 17 is a transparent insulating film with a thickness of approximately 800 mm. A lower electrode 12 was attached to the P-type substrate IO using Ag paste.

Next, AI Exband Metal 16 used in Example 1 above
The temperature of both the base heater 14 and the upper heater 15 was adjusted to about 300°C, and the pressure was set at about 300°C.
1 (H/Cl) for 1 minute, the A1 extended metal 1 (ia) broke through the PTG insulating film 17 and was able to obtain good ohmic contact. The current-voltage characteristics of this element were measured using a ΔM1 solar simulator. When measured, a fill factor of 0.74 was obtained.

<Example 3> A junction depth of 0.3. +1m N
A mold expansion 1&1Ftll is formed, and a lower electrode 12 of ΔG pace 1~ is attached to the P-type silicon substrate 10. Furthermore, an ITo film 1 of a transparent conductive film is formed on the N-type expansion 1tk and the layer 11.
8 is formed by vapor deposition (see FIG. 5). The ITO film 18 is provided as an anti-reflection film and to reduce the series resistance component of the element, and has a resistance of 50 to 100 Ω10. Next board #
An AI expander 1'' metal heater 6a with a diameter of 0.05 mm, a line width of 0.1 mm, and an aperture ratio of 93% is overlaid on the base heater 14. Both upper heaters 15 and 200°C
Adjust the temperature to about 20 (l kg/c,
When pressure was applied for one minute at I, good ohmic contact and strong adhesive strength were obtained. The current-voltage characteristics of this element were measured using an AM1 solar simulator and were found to be 0.7.
A fill factor of 4 was obtained.

<Example 4> In the process of Example 2, the back surface is left as a P-type silicon bare surface, and the PTG film 17 and the P-type silicon substrate 10 are
(See FIG. 6) and the base heater 14. After adjusting the temperature of both upper heaters 15 to 300° C., the pressure was applied to about 300 kg/cml. The current-voltage characteristics of this element were measured using an AMl solar simulator, and the fill factor was 0.69, and the adhesive strength was also very strong.

<Example 5> Exactly the same element used in Example 4 was subjected to Δl expansion]-
Direct I¥80μm Δl wire 1 instead of metal 16a
6b (see FIG. 3(A)) were arranged in a straight line at intervals of about 2 mm (see FIG. 7!!6). When heated and heated under the same conditions as in Example 4, a fill factor of 0.70 was obtained in terms of current-voltage characteristics, and the adhesive strength was strong.

Although the five embodiments have been described above, various combinations of the electrodes to be bonded and the elements to be bonded are possible. On the electrode side, the shape is 1'1 (ib (see Figure 3 (A)),
Cross maru (-1.16c (see Fig. 3 (B)) woven with wire and wire, extended band metal 16a (Fig. 3 (1))
In terms of materials, there are various plated products such as Δl, Ag, Ni, 8U, Cu, and CIl (Ni-plated). In addition, in the case of elements to be bonded, taking silicon as an example, there are elements with exposed silicon surfaces, lintitanate glass (PTG), phosphosilicate glass (
There are elements in which an insulating thin film such as PSG), titanate glass (1'G), or silicate glass (SG), or a transparent conductive M film such as ITo or 5n02 is formed on the wafer surface.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional electrode forming method in order of steps. FIG. 2 is a diagram illustrating the electrode forming method of the present invention. FIG. 3 is a partially enlarged view of a specific example of a group of thin metal wires. FIGS. 4 to 7 are diagrams each explaining the present invention in detail. 13-Solar cell element, 14-Base heater, 15-
Upper heater, 16 (16a, 16b, 16C)
- Group of thin metal wires. Applicant Sharp Co., Ltd. Agent Patent Attorney Hisao Komori Figure 11 Figure 3

Claims (1)

[Claims] After placing a group of thin metal wires for electrodes on the surface of the semiconductor element on which the +11PN junction is formed, the group of thin metal wires is connected to the surface of the semiconductor element by heating and pressurizing the group of metal thin wires with respect to the element. A method for forming electrodes of a semiconductor device, characterized in that: