Laser processing method for workpiece

摘要

During the performance of a laser processing step of applying a laser beam to a wafer to form modified layers inside the wafer respectively along division lines, a predetermined one of the modified layers already formed is imaged by a camera from the back side of the wafer with predetermined timing, and a positional deviation of the predetermined modified layer from the corresponding division line is detected to calculate a correction value. Then, the correction value is added to data on applied position of the laser beam to thereby make the applied position of the laser beam coincide with each division line. Accordingly, a positional deviation of the modified layer to be formed after this correction from each division line can be suppressed.

主权项

1. A laser processing method of performing laser processing to a workpiece having a plurality of devices respectively formed in a plurality of regions partitioned by a plurality of crossing process lines formed on a front side of said workpiece, said laser processing method comprising:
a holding step of holding the front side of said workpiece by using holding means to expose a back side of said workpiece; an alignment step of detecting said process lines from the back side of said workpiece held by said holding means to align each process line with a laser beam having a transmission wavelength to said workpiece; a laser processing step of applying said laser beam to said workpiece from the back side thereof along each process line in the condition where the focal point of said laser beam is set inside said workpiece after performing said alignment step, thereby forming a plurality of modified layers inside said workpiece respectively along said plurality of process lines; and a positional deviation correcting step of imaging a predetermined one of said modified layers formed inside said workpiece from the back side of said workpiece with predetermined timing by using imaging means during the performance of said laser processing step, detecting a positional deviation of said predetermined modified layer from a corresponding reference line of the imaging means to calculate a correction value, and adding said correction value to data on applied position of said laser beam to thereby make the applied position of said laser beam coincide with each process line.