JPS62150854A - Formation of electrode and apparatus for same - Google Patents

Abstract

PURPOSE:To efficiently and inexpensively form electrodes such as bump electrodes by press-bonding a melted ball formed by heating one end of a wire, and disconnecting it from the wire. CONSTITUTION:The end of a wire 17 is melted by a discharge torch 20, and a melted ball 21 is formed. The ball 21 is bonded to a pad 13 by pressing while an ultrasonic vibration is being applied by a capillary 15. A clamper 10 clamps the mid portion of a wire 17 to rise together with the capillary 15. Thus, the wire 17 is disconnected from the room portion 21a of the ball 21 to form a bump electrode 22. Since an electrode material is sequentially supplied in a wire state to form the electrode 22, the electrode can be efficiently formed. Thus, the inexpensive bump electrode can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a technique that is effective when applied to the formation of electrodes such as bump electrodes.

[Background Art] In tab method mounting in a tape carrier type semiconductor device, face-down bonding mounting, etc., an electrode called a bump electrode made of gold, solder, or the like is formed on a band of a pellet.

The bump electrode may be formed by means such as plating or vapor deposition, but in the case of the former plating, a long process is required to form an electrode with a predetermined layer thickness. On the other hand, the inventors have revealed that the latter method of vapor deposition results in high costs.

An example of a detailed description of bump electrode technology is "IC Mounting Technology" (Japan Microelectronics Association W), published by Kogyo Research Association Co., Ltd., January 15, 1980, PO2.

[Object of the Invention] An object of the present invention is to provide a technique that allows electrodes such as bump electrodes to be formed efficiently and at low cost.
.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the Invention] A brief overview of typical inventions disclosed in this application is as follows.

That is, it consists of a step of heating one end of the wire to form a molten ball, a step of crimping the molten ball in a predetermined position with a jig, and a step of cutting off the wire at the base of the crimped molten ball. As a result, the electrode material can be supplied as a wire using a mechanism similar to a wire bonding device for ball bonding, so that the electrode can be formed efficiently and at low cost.

Further, in the above, by mixing impurities into the wire, it is possible to promote embrittlement of the root portion of the molten ball and facilitate the division of the wire.

[Example] FIG. 1 (al to (el) are explanatory diagrams sequentially showing an electrode forming method according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing an electrode forming apparatus.

In the electrode forming apparatus 1 of this embodiment, each pellet 83 of a wafer is
Bump electrodes made of gold are formed on pads on the wafer, and the wafer has a predetermined circuit layer (not shown) formed on its surface.

The electrode forming apparatus 1 has almost the same mechanism as a so-called wire bonding apparatus, and can be obtained by only making slight improvements to the operation control software of the wire bonding apparatus. This electrode forming device 1
is equipped with a bonding stage 3 that holds the circuit forming surface of the wafer 2 facing upward, and an XY table 5 on which a bonding head 4, which is a bonding mechanism, is mounted. An arm 7 that engages with 6 is attached.

The driving eccentric cam 6 is rotated in the Z-axis direction by a DC servo motor 8, and is configured to move the arm 7 up and down.

On the other end side of the arm 7, that is, on the side of the bonding stage 3, there is provided a clamper lifter 11 having a first clamper 10 at its tip via a shaft support 9, and an ultrasonic horn 12. Usually, this clamper lifter 11 and an ultrasonic The horn 12 moves up and down about the shaft support 9 in an integrated manner. In this way, the arm 7 on the side of the bonding stage 3 is composed of two arm members, the clamper lifter 11 and the ultrasonic horn 12, because it controls the inertial movement of the ultrasonic horn 12 to control the inertial movement of the ultrasonic horn 12 and move the pin above the wafer 2.

This is to suppress the impact force on the pad 13 and to accurately apply the set load to the pad 13.

Note that the DC servo motor 8 and the XY table 5
The operation is electrically controlled by a control section 14.

On the other hand, a capillary 15 (crimping means) as a bonding tool is attached to the tip of the ultrasonic horn 12.
A wire 17 wound around a wire spool 16 is attached to this capillary 15 in a direction substantially perpendicular to the capillary 15 through a second clamper 18 and a first clamper 1o. It is inserted in a protruding state. In this embodiment, the wire 17 is mainly composed of gold (Au), but a trace amount of silicon (Si) is mixed therein.

The bonding stage 3 has a heater 1 buried inside.
By 9, il! The placed wafer 2 is always kept at a predetermined temperature,
(for example, about 200'C).

Next, the operation of this embodiment will be explained.

First, when the wafer 2 is placed on the pounding stage 3 and fixed by a fixing means (not shown), the XY table 5 is operated under the control of the control unit 14, and the tip of the capillary 15 is placed on a predetermined pad 13. (FIG. 1(a)). Next, a high voltage is applied between the discharging torch 20 and the tip of the wire 17 to melt the tip of the wire 17, forming a molten pole 21 (see the mountain in FIG. 1).

With the molten ball 21 formed in this way, the control unit 1
4, the DC servo motor 8 is activated, and the tip of the capillary 15 is lowered onto a predetermined pad 13 of the wafer 2. Further, the molten ball 21 is pressed and bonded to the pad 13 while being applied ultrasonic vibration by the capillary (FIG. 1(C)).

Next, the first clamper 10 clamps the middle portion of the wire 17 and moves up together with the capillary 15. As a result, tensile stress is applied to the wire 17, and the wire 17 is separated from the root portion 21a of the molten ball 21, forming the bump electrode 22 (FIG. 1(d)). Finally, the capillary 15 rises to a predetermined height to complete one cycle of bump electrode formation.

Here, in this embodiment, when the wire 17 is separated,
As shown in FIG. 1 (dl), by applying a slight tensile stress to the wire 17 by raising the first clamper 10, the wire 17 is easily separated from the root portion 21a of the molten ball 21. Molten ball 2 is mixed with silicon (Si) as an impurity in 17.
This is considered to be because brittleness is noticeable in the base portion 21a of wire 17, that is, near the crystal interface between the melted portion and the non-melted portion of wire 17, and the tensile stress in this portion is significantly reduced. In this way, since the wire 17 can be separated by applying a slight tensile stress, the bump electrode 22 can be formed in a good shape. Furthermore, this effectively prevents the pad 13 from peeling off due to the application of excessive tensile stress.

The bump electrodes 22 made of gold are formed on all the pads 13 on the wafer 2 by repeating the above steps a predetermined number of times. At this time, since the electrode forming apparatus of this embodiment has a mechanism similar to a wire bonding apparatus and has high positioning accuracy, it is possible to accurately form bump electrodes at precise positions on each band. be able to.

Further, since the bump electrode 22 is formed by sequentially supplying the electrode material in the form of a wire, efficient electrode formation is possible. Moreover, this makes it possible to form a bump electrode at low cost.

[Effects] (1) A step of heating one end of the wire to form a molten ball, a step of crimping the molten ball in a predetermined position with a jig, and cutting off the wire at the base of the crimped molten ball. By comprising these steps, the electrode material can be supplied as a wire, so the electrode can be formed efficiently and at low cost.

(2) By mixing impurities into the wire, the base of the molten ball becomes brittle, making it easier to cut the wire from that part.

(3) According to (2) above, a bump electrode with a good shape can be formed.

(4) With (2) above, it is possible to prevent the pad from peeling off due to the application of excessive tensile stress as the clamper rises.

(5) By using a mechanism similar to a wire bonding device for pole bonding, highly accurate operation control can be performed, so bump electrodes can be formed at accurate positions on each pad.

(6) According to (5) above, a semiconductor device with high electrical reliability can be provided.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, in the embodiment, only the case where electrodes are formed on a semiconductor wafer has been described, but the electrodes are formed on a semiconductor wafer that is divided into pellets or mounted on a substrate, etc. It may be a case.

In addition, although the electrode material has only been described as having gold (Au) as its main component and a small amount of silicon (Si) mixed in, any material may be used as long as it is compatible with the purpose of the present invention. For example, It may also be an alloy such as solder. Furthermore, the impurities are not limited to the silicon (St).

[Field of Application] In the above description, the invention made by the present inventor was mainly applied to the field of application, which is the formation of bump electrodes of pellets used in so-called tab-type semiconductor devices, but the present invention is not limited to this. This technique is also effective when applied to the formation of bump electrodes on pellets using face-down bonding, for example.

[Brief explanation of drawings]

FIGS. 1A to 1E are explanatory diagrams sequentially showing an electrode forming method according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing an electrode forming apparatus according to the embodiment. DESCRIPTION OF SYMBOLS 1... Electrode forming device, 2... Wafer, 3... Bonding stage, 4... Bonding head, 5...
・XY table, 6... Eccentric cam for driving, 7... Arm, 8... DC servo motor, 9... Shaft support, l
O...First clamper, 11...Clamper lifter, 1
2... Ultrasonic horn, 13... Pad, 14...
Control unit, 15... Capillary, 16... Wire spool, 17... Wire, 18... Second clamper, 1
9... Heater, 20... Discharge torch, 21... Melting ball, 21a... Root portion, 22... Bump electrode. No. i! ! ! ! 1 (e) Figure 2

Claims (1)

[Claims] 1. A step of heating one end of the wire to form a molten ball, a step of crimping the molten ball in a predetermined position with a jig, and cutting off the wire at the base of the crimped molten ball. An electrode forming method comprising the steps of: 2. The method for forming an electrode according to claim 1, wherein an impurity is added to the wire. 3. The wire is made of gold, and one of the impurities is silicon, and the addition rate is 1 ppm or more and 100 ppm.
3. The method for forming an electrode according to claim 2, characterized in that the electrode comprises m or less components. 4. It is characterized by having a heating means for forming a molten ball at one end of the wire, a crimping means for crimping the molten ball in a predetermined position, and a cutting means for cutting off the wire at the base of the crimped molten ball. Electrode forming device. 5. The heating means is a discharge torch or a hydrogen flame torch, and the crimping means holds the wire in a small hole and its position is controlled by a separately provided X, Y, Z drive positioning mechanism, such as a wire bonding device. 5. The electrode forming apparatus according to claim 4, wherein the capillary is a capillary, and the wire cutting means is a wire clamper mechanism.