JPH0456230A - Bump formation - Google Patents

Abstract

PURPOSE:To make the crest part of a bump electrode smooth while specifying the level of the bump electrode by a method wherein the crest part of the bump electrode formed by ball bonding process is irradiated with laser beams so as to melt down a part of said crest part by the energy of laser beams. CONSTITUTION:The crest part of a bump electrode 3 formed by ball bonding process is irradiated with laser beams 9 so as to melt down a part of the bump electrode crest part by the energy of the laser beams 9. For example, an Au ball is formed by nailheadbonding process to form the bump electrode 3 on an Al pad 2 provided on a semiconductor element 1. Next, the laser beams 9 is focussed through an image formation lens 8 to irradiate the crest part 4 of said bump electrode 3 for specific time so that the crest part irradiated with the laser beams 9 may be instantaneously melted down at high temperature by the energy of the laser to have a smooth surface taking a slightly spherical shape due to the surface tention of Au thereby enabling the level and the crest shape of the bump electtrode 3 to be specified.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a bump forming method for forming the head of a bump electrode formed on a semiconductor element.

Conventional technology In recent years, in order to meet the demands for increasing the number of pins in semiconductor devices and reducing the mounting area,
After forming bumps by plating gold (Au) through a barrier metal, or by welding a solder ball with solder coating on the surface of a steel (Cu) ball to the electrode pad, the bumps are formed by TAB or face-down method. However, the method of forming the Au plating bumps and solder ball bumps on the electrode pads of the semiconductor element requires special processes such as the above-mentioned barrier metal formation, and ,
Since the manufacturing equipment also requires a large amount of investment, the methods shown in Fig. 2 (a), (b),
As shown in the step-by-step side view of (C), bumps are formed on electrode pads by wire bonding, which has been conventionally used in the assembly of semiconductor devices.

First, as shown in FIG. 2(a), at the tip of the Au wire 6 drawn out from the capillary 7 located above the semiconductor element 1,
A ball 5 is formed by the discharge, and as the capillary 7 descends, the ball 5 is pressed against the electrode pad 2 of the semiconductor element 1, and is bonded by ultrasonic vibration and heat. (This is the same as wire bonding used in the assembly of semiconductor devices.)

Next, as shown in FIG. 2(b), the capillary 7 rises to a predetermined position and moves slightly, the Au wire 6 is damaged by shearing, and then due to the movement of the capillary 7 and the wire clamper, As shown in FIG. 2(C), the Au wire 6 is torn off at the part that has suffered the shear damage, and a bump electrode 3 is formed on the electrode pad 2, but the ball 5 formed by the discharge The state of the Au wire that is torn off varies depending on the size variation and the eccentricity between the Au wire 6 and the ball 5, etc., and the height and size of the formed bump electrode head 4 are shown in Figure 3. Variations occur as shown in the example.

Problems to be Solved by the Invention As mentioned above, in the method of forming bump electrodes using the bonding method, the head of the formed bump electrode may , height 2, size and shape vary,
In particular, variations in height have had a serious drawback in that bump electrodes with low heights are not electrically connected when mounting by TAB or face-down.

Means for Solving the Problems In order to solve the above problems, the present invention irradiates a bump electrode head formed by a ball bonding method with a laser beam to partially melt it.

A laser beam is irradiated onto the bump electrode head formed by the action pole bonding method, and the energy of the laser beam melts a part of the bump electrode head, smoothing the bump electrode head surface and reducing the bump electrode height. Make it constant.

Example An embodiment of the present invention will be described with reference to FIG.

FIGS. 1(a) and 1(b) are diagrams illustrating the molding state of a bump electrode according to an embodiment.

In FIG. 1(a), A[
An Au ball is bonded onto the pad 2 by the nail-to-rad bonding method used for assembling semiconductor devices on boats to form a bump electrode 3, and the head of the bump electrode has a height of 1.

There are variations in size and shape.

The laser beam 9 is focused through an imaging lens 8 located at a height with a predetermined distance between it and the upper surface of the semiconductor element l, and is irradiated onto the bump electrode head 4 for a predetermined time only. Ru.

The part of the bump electrode head 4 that is irradiated with the laser beam is
The laser energy instantaneously raises the temperature and melts the surface, and the surface tension of Au forms a slightly spherical shape, making the height of the bump electrode 3 and the shape of the bump electrode head 4 constant.

Effects of the Invention As described above, in the bump forming method of the present invention, the bump electrode head formed on a semiconductor element is melt-molded using laser energy, so the height of the bump electrode and the shape of the bump electrode head are controlled. This is made constant and has the effect of significantly improving the reliability of semiconductor devices having bump electrodes.

[Brief explanation of drawings]

Fig. 1 is a side view showing an overview of a bump forming method according to an embodiment of the present invention, Fig. 2 is a side view showing the process order for explaining the formation of bump electrodes by a conventional pole bonding method, and Fig. 3 is a side view showing an outline of a bump forming method according to an embodiment of the present invention. FIG. 3 is a side view illustrating the size and shape of the electrode head. DESCRIPTION OF SYMBOLS 1... Semiconductor element, 3... Bump electrode, 4... Bump electrode head, 9... Laser beam.

Claims (1)

[Claims] A bump forming method characterized by irradiating a laser beam onto the top of a bump electrode formed by a ball bonding method, and melting a portion of the bump electrode head with the energy of the laser beam.