JP2000124176A - Method for enhancing semiconductor chip transverse strength using laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease grinding scratches by a method wherein a laser irradiates a backside of a wafer ground so as to reach a predetermined thickness by a whetstone, so that the surface is partially molten. SOLUTION: Grinding scratches occurred in grinding are left behind on a backside of a semiconductor chip, and a semiconductor chip 4 is mounted on a stand having a clearance of 10 mm, and a force is applied on a center part of the chip to acquire a magnitude of a force when the semiconductor chip is broken, and when transverse strength of the semiconductor chip is measured, it is made clear that each depth of scratches influences the transverse strength. A laser irradiates backside of a wafer ground so as to reach a predetermined thickness by a whetstone to melt the surface partially. More specifically, a YAG laser 2 is irradiated on the back surface of a wafer 1 while scanning. The irradiated semiconductor chip is cut out, and when the transverse strength is measured, the grinding scratches are flattened by laser irradiation to be in a substantially mirror face, and it is realized that the transverse strength is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the bending strength of a semiconductor chip used in a semiconductor device by using a laser.

[0002]

2. Description of the Related Art As semiconductor devices become thinner, there is an increasing demand for thinner semiconductor chips. In general, as a method of thinning a semiconductor chip, a method of polishing a back surface of a circuit-formed wafer with a grindstone and a method of etching with a chemical have been used.

[0003]

The method using a grindstone is
Although it can be applied with relatively small equipment, semiconductor chips using this method have polishing scratches on the back of the chip,
Stress concentration occurred in that portion, and there was an essential problem that bending strength was low. In addition, although the etching method solves the above-mentioned problems, it is necessary to control many parameters accurately in order to uniformly etch the entire wafer, and it is necessary to pay attention to the handling of chemicals. Equipment was needed.

[0004]

SUMMARY OF THE INVENTION The present invention provides a method for solving the above-mentioned problems, and more specifically, irradiates a laser to the back surface of a wafer polished to a predetermined thickness with a grindstone to partially cover the front surface. This is a method of reducing the polishing scratches by melting the polishing.

[0005]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 2 shows the back surface of the semiconductor chip 4, and polishing flaws 5 generated during polishing remain. FIG. 3 shows a method for measuring the bending strength of a semiconductor chip. The semiconductor chip 4 is placed on a receiving table 7 having a gap of 10 mm, and a force 6 is applied to the center of the chip to break the semiconductor chip 4. The magnitude of the force 6 is determined. Table 1 shows an example of the bending strength of the semiconductor chip obtained by the method of FIG. 3, and shows that the depth of the flaw affects the bending strength.

[0006]

[Table 1]

FIG. 1 shows an outline of the present invention, in which a laser 2 is irradiated on the back surface of a wafer 1 while scanning it. As an example, after irradiating the back surface of the wafer with a 20 W YAG laser, a semiconductor chip is cut out and the bending strength is measured. Table 2 shows the result. It can be seen that the bending strength is improved.

[0008]

[Table 2]

It is clear that the method of the present invention can be applied to a laser capable of continuously or periodically irradiating the energy having the strength to slightly melt the wafer surface, without being limited to the type of laser or the type of oscillation. is there. ,

[0010]

According to the present invention, the following effects can be expected. (1) Polishing scratches are reduced, and the bending strength of the semiconductor chip is improved. (2) This is a dry process in the atmosphere, and can be performed with small-scale and low-cost equipment as compared with the etching method. (3) Since no chemical is used, there are few restrictions on the installation location of the equipment. (4) High-speed processing is possible

[0011]

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of the present invention.

FIG. 2 is a perspective view showing a back surface of the semiconductor chip.

FIG. 3 is a view showing a method for measuring a bending strength of a semiconductor chip.

[Explanation of symbols]

Reference Signs List 1 wafer 2 laser 3 laser oscillator 4 semiconductor chip 5 polishing flaw 6 force 7 cradle

Claims (1)

[Claims] 1. A method for improving the bending strength of a semiconductor chip by scanning a back surface of the semiconductor chip with a laser having an intensity capable of slightly melting the chip surface.