Laser processing method

Abstract

A laser processing method enables a grinding skin to be formed in a wafer along a separation channel and ensures that a functional layer formed on the front side of a substrate may not be damaged. The laser processing method includes a wafer holding step where a wafer is held on a workpiece chuck table in a manner that the back of a substrate is on the upper side; a height position measuring step where the back of the substrate of the wafer being held on the chuck table is irradiated along the separation channel, and where a first height position from the upper surface of the chuck table to the back of the substrate and a second height position from the upper surface of the chuck table to the front of the substrate are measured along the separation channel according to the reflected lights reflected by the back and front of the substrate; and a grinding skin forming step where laser beams converge at the middle of the first height position and the second height position obtained from the previous step to irradiate along the separation channel, thereby forming a grinding skin which is formed in the substrate along the separation channel and may not reach the functional layer.

Description

technical field [0001] The present invention relates to a laser processing method for forming a degenerated layer inside a wafer such as a semiconductor wafer or an optical device wafer. Background technique [0002] In the semiconductor device manufacturing process, a plurality of regions are divided on the surface of a roughly disc-shaped semiconductor wafer by dividing lines called streets arranged in a grid pattern, and ICs, ICs, etc. are formed in the divided regions. LSI and other devices. And, by cutting the semiconductor wafer along the lanes, the regions where the devices are formed are divided, thereby manufacturing individual semiconductor devices. Furthermore, optical device wafers in which gallium nitride-based compound semiconductors and the like are stacked on the surface of a sapphire substrate are also cut along the streets to be divided into individual optical devices such as light-emitting diodes and laser diodes, and are widely used in electrical equipme...

AI Technical Summary

Problems solved by technology

In this way, if the altered layer formed on the substrate by irradiation of laser light reaches the functional layer or approaches the altered layer at a very short distance, there will be a problem that the functional layer will be damaged due to the influence of energy generated by the irradiation of laser light.

Images