Patent ID: 11945049
Assignee: DISCO CORPORATION
Field: Measurement (Instruments)
Classification: CPC B  G  H | IPC B  G  H

Claim 11:
12. A SiC wafer manufacturing method for manufacturing a SiC wafer from a SiC ingot having an end surface, the SiC wafer manufacturing method comprising:
applying a test laser beam to the SiC ingot in a predetermined area in a condition where the focal point of the test laser beam is set inside the SiC ingot at a predetermined depth from the end surface of the SiC ingot, the predetermined depth corresponding to the thickness of the SiC wafer to be manufactured, the test laser beam having a transmission wavelength transmissible through SiC, the verifying step comprising:
setting the test laser beam to a first power;
forming a first test separation layer inside the SiC ingot at the predetermined depth, the first test separation layer having a first test modified portion at the predetermined depth where SiC is separated into Si and C and first test cracks extending from the first test modified portion along a c-plane in the SiC ingot;
forming a second test separation layer by providing relative movement between the SiC ingot and the test laser beam in a direction perpendicular to a length of the first test modified portion and forming a second test modified portion parallel to the first test modified portion and aligned therewith,
wherein the second test modified portion is located at the predetermined depth where SiC is separated into Si and C, wherein second test cracks extend from the second test modified portion along a c-plane in the SiC ingot;

confirming whether the first and second test cracks have been formed such that the first and second test cracks overlap in the direction perpendicular to the length of the first test modified layer; and
with the test laser beam set at a second power, repeating, as necessary, the forming the first test separation layer step, the forming the second test separation layer step, and the confirming step after providing further relative movement between the SiC ingot and the test laser beam in a direction parallel to the length of the first test modified portion until the first and second test cracks have been formed such that the first and second test cracks overlap in the direction perpendicular to the length of the first test modified layer;

the SiC wafer manufacturing method further comprising:
applying a laser beam to the SiC ingot in a condition where the focal point of the laser beam is set inside the SiC ingot at the predetermined depth from the end surface of the SiC ingot after performing the verifying step, the predetermined depth corresponding to the thickness of the SiC wafer to be manufactured, the laser beam having a transmission wavelength transmissible through SiC, thereby forming the separation layer inside the SiC ingot at the predetermined depth, the separation layer inside the SiC ingot having a modified portion where SiC is separated into Si and C and cracks extending from the modified portion along the c-plane in the SiC ingot; and

separating the SiC wafer from the SiC ingot along the separation layer after performing the separation layer forming step.