JPH03273637A - Bump forming method - Google Patents

Abstract

PURPOSE:To increase connecting strength in a simple step by using an ordinary wire bonding device and to cope with the production of a small amount of many kinds of products readily by fusing the tip of a wire that is supplied into a wire bonding device, forming a ball, and forming the electrode by thermal contact bonding of the ball in the specified position. CONSTITUTION:A wire 12 comprising Au-2Si alloy is inserted through a capillary 13 of a wire bonding device. Then the discharge voltage of 30-80 V is applied across a discharge electrode and the tip of the above described thin wire. Discharging is generated, and the tip of the gold thin wire is heated and fused. Thus a ball 11 is formed. Then, the ball undergoes thermal contact bonding to a bonding pad 22 on the SiO2 surface of a semiconductor substrate 21. After the completion of the thermal contact bonding, the gold thin wire is lifted, the gold thin wire is cut out from the ball 11 and a bump 24 is formed. As the wire used, ordinary wire used in a wire bonding method can be utilized, but gold-based alloy and lead-based alloy are preferable.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for forming bump electrodes, and particularly to a method for forming bump electrodes that can easily make electrical connections in semiconductor devices, hybrid integrated circuits, etc. It is something.

[Prior Art] A method of using bump electrodes for electrical connection in semiconductor devices, hybrid integrated circuits, etc. is conventionally known along with wire bonding.

Bump electrodes of this type are sometimes formed on the bonding pads of semiconductor devices, hybrid integrated circuits, etc., and sometimes formed on the side that faces and connects to the bonding pads, but conventionally they are formed on the bonding pads. The bump electrode has a structure shown in FIG. This bump electrode is formed by the following process.

That is, (1) a step of removing the natural oxide film on the surface of the bonding pad 2 in the opening of the surface protective film 3 on the surface of the substrate 5i02 by sputter etching or chemical etching, (2) removing the Ti-W film 4 and the Au film. (3) Next, applying a photoresist by a photolithography method and removing the photoresist coated on the bump plating forming area; (4) Electroplating the bump plating forming area from which the photoresist has been removed. (5) Further removing the photoresist and removing the deposited film other than the lower part of the Au bump electrode 6 by chemical etching; (6) Finally, the plated Au is heat-treated. Step of Relaxing and Softening Residual Stress in Bump Electrode 6 [Problems to be Solved by the Invention] However, such a method of forming a bump electrode requires many complicated steps as described above; When forming bump electrodes using the photolithography method, there are problems such as having to prepare a different photomask for each product because the positions of the bump electrodes are different, making it difficult to form bump electrodes easily.

As a result of studying the above-mentioned problems, the inventors of the present invention have developed a bump that solves the problems, has stable shape and dimensions, has excellent adhesive strength, and is capable of responding to low-volume, high-mix production. An object of the present invention is to provide a method for forming an electrode.

[Means for Solving the Problems] The object of the present invention is to provide a method for forming bump electrodes at positions for electrical connection, which is characterized by comprising the following steps (a) to (b). This is achieved by a method for forming bump electrodes.

(b) A step of supplying a wire made of metal or alloy to a wire bonding device, (b) A step of melting the tip of the supplied wire to form a ball, (c) A step of placing the formed wire at a position where an electrical connection is to be made. Step of thermocompression bonding; 2) Step of separating the thermocompression bonded ball from the wire. Next, the present invention will be described in more detail.

The wires used in the present invention include wires commonly used in wire bonding methods made of gold, silver, copper, aluminum, lead, brazing metal, or alloys thereof, but preferably full alloys, lead wires, etc. type alloy is better.

For all alloys, Au-5t, Au-Ge, ^u-5n
Examples of lead-based alloys include Pb-Ag,
Examples include alloys such as PPb-5n-A. Among these, it is preferable to use a full alloy in consideration of reliability and the like.

The wire bonding device used in the present invention includes:
Equipment equipped with capillaries commonly used in ball bonding methods can be used.

The means of melting the tip of the wire passed through the capillary of the wire bonding device to form a ball include the c-ball bonding method, which includes a method of discharging between the tip of the wire and a movable electrode, a method using oxyhydrogen flame, etc. The normal ball-making method is used.

The ball thus formed is thermocompression bonded to a desired position on a bonding pad or lead of a semiconductor device, hybrid integrated circuit, or the like.

In this case, if thermocompression bonding at a low temperature is required, it is preferable to use a thermosonic method in which ultrasonic waves are applied to the capillary.

The ball is formed using spark discharge, hydrogen torch, etc.

After the ball thus obtained is bonded by thermocompression, the wire can be cut by pulling up the wire.

Note that the shape, dimensions, etc. of the bump electrode can be changed as appropriate by controlling the diameter of the wire, the conditions for forming the ball, etc.

[Example] Next, an example of the present invention will be described using Figure 's1 and Figure 's2, but the present invention is not limited thereto.

FIG. 1 is a cross-sectional view of a ball formed at the tip of a wire passed through a capillary of a wire bonding device;
1 is a ball, 12 is a wire, and 13 is a capillary.

FIG. 2 is a cross-sectional view of a bump electrode installed on a bonding pad of a semiconductor device, where 21 is a semiconductor substrate, 22
23 is a surface protection film, and 24 is a bump electrode.

The wire 12 is made of u-2Si alloy and has a diameter of 0. O
Using a 1-inch thin gold wire, this thin wire is passed through the capillary 13 of the wire bonding device. Next, a voltage of 30V to 80V (capacitor capacity 1000 to 50009F), preferably 5V is applied between the discharge electrode (not shown) and the tip of the thin wire.
A discharge voltage of 0 V is applied to generate a discharge, thereby heating and melting the tip of the thin gold wire to form the ball 11. Next, the ball 11 is placed on a 5in2 semiconductor substrate 21 made of SL.
It is thermocompressed to the bonding pad 22 on the surface. The bonding load at this time is 50 g to 100 g. The bonding temperature is 150° C. to 250° C., and after the thermocompression bonding is completed, the thin gold wire is pulled up and separated from the ball 11 to form a bump electrode.

[Effects of the Invention] The method for forming a bump electrode of the present invention is such that the bump electrode is formed by thermocompression bonding a ball of wire supplied to a wire bonding device at a predetermined position, so that the following excellent effects can be obtained. .

(a) Bump electrodes can be formed in a simple process using an ordinary wire bonding device, and it can easily respond to low-volume, high-mix production.

(b) Thermocompression bonding can increase the strength of the connection between the bump electrode and the bonding pad or lead.

(c) The shape, dimensions, etc. of the bump electrode can be freely controlled and can be formed stably.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a ball formed at the tip of a wire passed through a capillary of a wire bonding apparatus used in the present invention, and FIG. FIG. 3 is a cross-sectional view showing a bump electrode placed above. FIG. 3 is a cross-sectional view showing a bump electrode formed on a conventional bonding pad. Explanation of symbols 1... Substrate 2.22 3.23... Surface protective film 5--Alli 6- 11... Ball 12 13... Capillary 24... Bump electrode/Bonding bat 4... Ti-W film... Au bump electrode...Wire 21...Semiconductor substrate Figure 1 Figure 2

Claims (1)

[Scope of Claims] A method for forming a bump electrode at a position for electrical connection, the method comprising the following steps (a) to (d). (b) A step of supplying a wire made of metal or alloy to a wire bonding device, (b) A step of melting the tip of the supplied wire to form a ball, (c) A step of placing the formed wire at a position where an electrical connection is to be made. a step of thermocompression bonding; (d) a step of separating the thermocompression bonded ball from the wire;