WAFER THINNING METHOD

摘要

Disclosed herein is a wafer thinning method for thinning a wafer formed from an SiC substrate having a first surface and a second surface opposite to the first surface. The wafer thinning method includes a separation start point forming step of applying the laser beam to the second surface as relatively moving the focal point and the SiC substrate to thereby form a modified layer parallel to the first surface and cracks inside the SiC substrate at the predetermined depth, thus forming a separation start point, and a wafer thinning step of applying an external force to the wafer, thereby separating the wafer into a first wafer having the first surface of the SiC substrate and a second wafer having the second surface of the SiC substrate at the separation start point.

主权项

1. A wafer thinning method for thinning a wafer 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 having a plurality of devices formed on said first surface of said SiC substrate, said wafer thinning 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 second surface, which depth corresponds to a vertical position near said first surface of said SiC substrate, and next applying said laser beam to said second surface as relatively moving said focal point and said SiC substrate to thereby form a modified layer parallel to said first surface inside said SiC substrate at said predetermined depth and also form cracks extending from said modified layer along said c-plane, thus forming a separation start point; and a wafer thinning step of applying an external force to said wafer after performing said separation start point forming 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, whereby the thickness of said wafer is reduced to the thickness of said first wafer having said first surface of said SiC substrate; said separation start point forming step including
a modified layer forming step of relatively moving the focal point of said laser beam in a first direction perpendicular to a second direction where said c-axis is inclined by an off angle with respect to a normal to said second surface and said off angle is formed between said second surface and said c-plane, thereby linearly forming said modified layer extending in said first direction, andan indexing step of relatively moving said focal point in said second direction to thereby index said focal point by a predetermined amount.