JPS59115522A - Formation of electrode for semiconductor device - Google Patents

Abstract

PURPOSE:To enable to complete a wire connection work by performing only one process for heating and pressurization by a method wherein, after conductive paste has been printed and sintered on the surface of a semiconductor wafer, a fine metal wire group is placed thereon and the fine metal wires are heated and pressurized for the wafer. CONSTITUTION:Al paste 2 is printed and sintered on the surface of the Si wafer 1 formed on a P-N junction part. An alloy layer 2 and a duct 3 are formed by performing a sintering. Then, they are placed between heaters 7 and 7' without removing the duct 3. At the same time, a plurality of lead wire groups 5' are arranged between the heater 7' and the duct 3. the heaters 7 and 7' are heated up under the condition where the above-mentioned positional relations are maintained and, at the same time, said heaters 7 and 7' are moved in the direction of the arrows P and P as shown in the diagram, and the wafer 1 and the wire group 5' are pressurized. As a result, the wire group 5' enters into the duct 3, the wire group 5' comes in contact with the alloy layer 2 and fixed. To be more precise, attracting force is generated between the wire group 5' and the duct 3 and the wire group 5' and the layer 2, and an excellent ohmic contact state is formed between the wire group 5' and the layer 2 by the above-mentioned attracting force.

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 leather bonding method or a conductive paste printing method. However, the vacuum evaporation method is unsuitable for low price and mass production in terms of time and cost, and also has the disadvantage of large loss of evaporated metal, so currently, the printing method of conductive paste is mainstream. It is becoming. Figure 1 shows a typical method of printing conductive paste.

Show the law. First, A1 paste 2 is printed and fired on the lower surface of silicon wafer 1 (step (A)). AI paste 2
The dust 3 formed on the lower surface is an oxide film formed during the firing step. Next, chemically or physically dust 3
is removed (step (B)), and in order to enable soldering, Ag paste 4 is printed on the exposed AI paste 2 (step (C)), dried, and fired (step (C)).
D)).

After going through the above steps, the lead wire 5 is placed on the Ag base 4.
Solder with solder 6 to complete the 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 requires the steps of printing, baking, and attaching the paste.
The process became complicated and it was not possible to achieve sufficient cost reduction.

<Object of the Invention> An object of the invention is to provide a method for forming electrodes of a semiconductor device, which allows connection of lead wires to be completed in one step.

<Structure of the Invention> The present invention involves firing a conductive paste for electrodes, placing a group of fine metal wires on the oxide film, and heating and heating it without removing the oxide film covering the formed alloy. It is characterized in that the group of metal fine wires is directly connected to the semiconductor wafer surface by applying pressure.

Example 21 No. 1 is a diagram illustrating the electrode forming method of the present invention.

First, Δ1 paste 2 is printed on the surface of a silicon wafer 1 in the same manner as in step (A) of FIG. 1, and then baked. By firing, alloy pre-2 and dust 3 are formed, but dust 3
without removing it, place it as it is between the heaters 7 and 7' arranged above and below.

At the same time, a plurality of lead wires 5', which are an example of a group of thin metal wires, are arranged between the lower heater 7' and the dust 3. While maintaining the above two positional relationships, the upper and lower heaters 7 and 7' are heated and moved in the directions of arrows P and P' to pressurize the wafer and lead wire 5'. Heating and pressurization are performed at, for example, 300°C to 400°C, 2001c g
/ cnT for 1 minute. Figure 3 shows the structure of the device obtained by the above steps. As shown in Figure 1-1, by placing the lead wire 5' on the dust 3 and applying heat and pressure, the lead wire 5' enters into the dust 3, and the lead wire 5' is placed on the alloy layer 2. It can be seen that they are in contact and fixed. That is, by the heating and pressurizing process described above, the lead wire 5' and the three dust particles and the lead wire 5' and the alloy layer 2 are separated.
Physical and chemical adsorption forces are formed between them, and these adsorption forces form a good ohmic contact state between the lead wire 5' and the alloy 1772. Like this △1 paste 2
The wire connection can be completed simply by stacking the lead wire 5' on the silicon wafer that has been fired and applying pressure while heating it. In addition, as the metal fine wire group, -1
In place of the wire, a mesh or woven wire may be used.

In the conventional electrode formation method shown in No. 1 and 1, it takes more than 2 hours to remove the dust chemically (for example, by aqua regia etching), and it takes more than 2 hours to remove the dust physically (for example, with a wire brush). According to experiments conducted by the inventors, the time required to connect the lead wires using method 1 is 10 to 2 minutes.
It was 0 seconds. Further, the electrical characteristics in this case were no different from the characteristics of the wire connection state obtained by the conventional method, and the adhesive force between the lead wire and the alloy W was also sufficient.

<Effects of the Invention> As described above, according to the present invention, printing, baking, semi-r1. + (= A series of machining is not required at all, and the wiring can be completed with only one process of heating and pressurizing, which not only greatly simplifies the process, but also reduces the time required for wiring. There is also the advantage of 9) which can greatly reduce costs.

[Brief explanation of the drawing]

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 diagram showing the state of the lead wire connection of the wafer when the electrode forming method of the present invention is carried out. 1 - Silicon wafer, 2 - AI paste, 3 - Dust, 4 - Ag paste, 5.5' - Lead wire, 6 - Half ■ 1, 7.7' - Heater. Funeral 1 illustration year 21-J 'ji3rJ

Claims (1)

[Claims] (Print a conductive paste for electrodes on the surface of the semiconductor wafer on which the IIPN junction is formed, and bake it to form an alloy layer,
After placing a group of metal fine wires on the oxide film covering the alloy layer,
1. A method of forming electrodes for a semiconductor device, characterized in that the thin metal wires are connected to a surface of a semiconductor wafer by heating and pressurizing the group of thin metal wires with respect to the wafer.