| CPC B28D 5/0011 (2013.01) [B23K 26/38 (2013.01); B28D 5/0052 (2013.01)] | 6 Claims |
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1. A method of manufacturing a substrate from a cylindrical workpiece having a first circular surface and a second circular surface positioned opposite the first circular surface, the method comprising:
a peel-off layer forming step of repeatedly moving the workpiece and a focused spot, the focused spot being positioned within the workpiece, of a laser beam that is applied to the workpiece and has a wavelength transmittable through a material of the workpiece, relatively to each other in a processing-feed direction parallel to the first circular surface, thereby forming a peel-off layer in each of a plurality of areas in the workpiece, the areas extending along the processing-feed direction, the peel-off layer containing modified regions formed around a plurality of the focused spots and cracks developed from the modified regions; and
a separating step of separating the substrate from the workpiece along a plurality of the peel-off layers that act as separation initiating points,
wherein the plurality of areas include
a first outer area at a first end of the workpiece and included in one of two semicylindrical regions of the workpiece, the two semicylindrical regions having a common boundary plane extending through a center of the workpiece and parallel to the processing-feed direction,
a first intermediate area included in the one of the two semicylindrical regions and closer to the center of the workpiece than the first outer area in a Y-direction along the first circular surface or the second circular surface of the workpiece,
a first inner area included in the one of the two semicylindrical regions and closer to the center of the workpiece than the first intermediate area in the Y-direction along the first circular surface or the second circular surface of the workpiece,
a second outer area at a second end of the workpiece, wherein the second end is opposite to the first end, the second outer area included in the other one of the two semicylindrical regions,
a second intermediate area included in the other one of the two semicylindrical regions and closer to the center of the workpiece than the second outer area in the Y-direction along the first circular surface or the second circular surface of the workpiece, and
a second inner area included in the other one of the two semicylindrical regions and closer to the center of the workpiece than the second intermediate area in the Y-direction along the first circular surface or the second circular surface of the workpiece, and
the peel-off layer forming step includes the steps of forming a peel-off layer initially in the first outer area and forming a peel-off layer finally in the first inner area or the second inner area.
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