Patent ID: 9620415
Date: 2017-04-11
CPC Classifications: B23K,H01L

Claim:
1. A wafer processing method for dividing a wafer into individual device chips, said wafer being formed from an SiC substrate having a first surface, a second surface opposite to said first surface, a c-axis extending from said first surface to said second surface, and a c-plane perpendicular to said c-axis, said wafer processing method comprising: a separation start point forming step of setting the focal point of a laser beam having a transmission wavelength to said SiC substrate inside said SiC substrate at a predetermined depth from said first surface or said second surface, which depth corresponds to the finished thickness of each device chip, and next applying said laser beam to said first surface or said second surface as relatively moving said focal point and said SiC substrate to thereby form a modified layer parallel to said first surface and cracks extending from said modified layer along said c-plane, thus forming a separation start point; a device forming step of forming a plurality of devices on said first surface of said SiC substrate in a plurality of separate regions defined by a plurality of crossing division lines, after performing said separation start point forming step; a division start point forming step of forming a division start point having a depth corresponding to the finished thickness of each device chip along each division line formed on said first surface, after performing said device forming step; a protective member providing step of providing a protective member on said first surface of said SiC substrate after performing said division start point forming step; and a wafer separating step of applying an external force to said wafer after performing said protective member providing step, thereby separating said wafer into a first wafer having said first surface of said SiC substrate and a second wafer having said second surface of said SiC substrate at said separation start point; said separation start point forming step including