Method and apparatus for detecting facet region, wafer producing method, and laser processing apparatus

Abstract

A method of detecting a Facet region includes: a fluorescence luminance detecting step of detecting fluorescence luminance unique to SiC by irradiating a SiC ingot with exciting light having a predetermined wavelength from a top surface of the SiC ingot; and a coordinate setting step of setting a region in which the fluorescence luminance is equal to or higher than a predetermined value in the fluorescence luminance detecting step as a non-Facet region, setting a region in which the fluorescence luminance is lower than the predetermined value in the fluorescence luminance detecting step as a Facet region, and setting coordinates of a boundary between the Facet region and the non-Facet region.

What is claimed is: 
     
         1 . An apparatus for detecting a Facet region of a SiC ingot, the apparatus comprising:
 fluorescence luminance detecting means detecting fluorescence luminance unique to SiC by irradiating the SiC ingot with exciting light having a predetermined wavelength from a top surface of the SiC ingot; and   coordinate setting means setting a region in which the fluorescence luminance detected by the fluorescence luminance detecting means is equal to or higher than a predetermined value as a non-Facet region, setting a region in which the fluorescence luminance is lower than the predetermined value as a Facet region, and setting coordinates of a boundary between the Facet region and the non-Facet region.   
     
     
         2 . A laser processing apparatus for forming a peeling layer in a SiC ingot, the laser processing apparatus comprising:
 a holding table configured to hold the SiC ingot;   fluorescence luminance detecting means detecting fluorescence luminance unique to SiC by irradiating the SiC ingot with exciting light having a predetermined wavelength from a top surface of the SiC ingot;   coordinate setting means setting, as an X-axis, a direction orthogonal to a direction in which a c-plane is inclined with respect to the top surface of the SiC ingot and an off angle is formed, setting a direction orthogonal to the X-axis as a Y-axis, setting a region in which the fluorescence luminance detected by the fluorescence luminance detecting means is equal to or higher than a predetermined value as a non-Facet region, setting a region in which the fluorescence luminance is lower than the predetermined value as a Facet region, and setting X-coordinates and Y-coordinates of a boundary between the Facet region and the non-Facet region;   a laser beam irradiating unit including a condenser that forms a peeling layer in which SiC is separated into Si and C and a crack extends along the c-plane, by positioning a focusing point of a laser beam having a wavelength transmissible through SiC at a depth corresponding to thickness of a wafer to be produced from the top surface of the SiC ingot, and irradiating the SiC ingot with the laser beam;   an X-axis feeding mechanism configured to processing-feed the holding table and the condenser relative to each other in an X-axis direction;   a Y-axis feeding mechanism configured to indexing-feed the holding table and the condenser relative to each other in a Y-axis direction; and   a control unit configured to increase energy of the laser beam and raise a position of the condenser at a time of irradiating the Facet region with the laser beam with respect to the energy of the laser beam and the position of the condenser at a time of irradiating the non-Facet region with the laser beam on a basis of the X-coordinates and Y-coordinates of the boundary between the Facet region and the non-Facet region.