Patent ID: 8704126

Claim:
A laser beam machining apparatus comprising: a wafer including an arcuate chamfered part formed on an outer periphery of the wafer; a chuck table for holding said wafer; laser beam irradiation means for irradiating said wafer held on said chuck table with a laser beam; machining feeding means for putting said chuck table and said laser beam irradiation means into relative movement in a machining feed direction (X-axis direction); indexing feeding means for putting said chuck table and said laser beam irradiation means into relative movement in an indexing feed direction (Y-axis direction) orthogonal to said machining feed direction (X-axis direction); X-axis direction position detecting means for detecting an X-axis direction position of said chuck table; Y-axis direction position detecting means for detecting a Y-axis direction position of said chuck table; and control means for controlling said laser beam irradiation means, said machining feeding means and said indexing feeding means on the basis of signals from said X-axis direction position detecting means and said Y-axis direction position detecting means, wherein said laser beam irradiation means includes a laser beam oscillator for oscillating a laser beam with such a wavelength as to be transmitted through said wafer, repetition frequency setting means for setting a repetition frequency of pulses in said laser beam oscillated from said laser beam oscillator, and a Q switch for outputting a gate signal to said laser beam oscillator correspondingly to said repetition frequency set by said repetition frequency setting means; and said control means includes a memory for storing coordinates of said arcuate chamfered part formed at an outer periphery of said wafer and coordinates of a flat surface part surrounded by said chamfer part, and automatically controls said repetition frequency setting means so as to set a flat surface repetition frequency and a chamfered part repetition frequency based on said stored coordinates, said X-axis direction position detected by said X-axis direction position detection means, and said Y-axis direction position detected by said Y-axis direction position detecting means; wherein the flat surface repetition frequency is the frequency of pulses in a laser beam with which to irradiate said flat surface part to a value suitable for machining of said wafer, and the chamfered part repetition frequency is the repetition frequency of pulses in a laser beam with which to irradiate said chamfered part, wherein the chamfered part repetition frequency is set to a value higher than said flat surface repetition frequency.