Patent ID: 8835802

Claim:
A method for producing thin wafers from a brittle crystalline material, without causing kerf loss, by cleaving said material at a chosen plane in said material, comprising the steps: providing a crystal of said material with a flat surface parallel to said chosen plane; providing a source of radiation to which, over at least one range of intensities of said radiation, said material has an absorbance that increases with the intensity of said radiation, such that said material is relatively transparent at the lowest intensity in said range, and such that said material efficiently absorbs said radiation at the highest intensity in said range; focusing said radiation on said plane, from a direction substantially normal to said plane, and passing through said flat surface, to converge within said crystal so as to create in said crystal a first region of maximum intensity of said radiation; adjusting said source of radiation so that as said radiation is converging to said first region of maximum intensity, before reaching said first region, the intensity of said radiation is low enough so that said material is relatively transparent but at said first region, the intensity is great enough so that said material efficiently absorbs said radiation, thereby causing local heating at said first region while generally avoiding heating those regions surrounding said first region, causing said regions surrounding said first region to have a lower temperature than said first region, thereby causing tensile stresses in said material in said surrounding regions; locating said first region of maximum intensity on said chosen plane so it is near a first area on said plane where cleavage is intended to take place, at such a distance from said first area such that said area is in one of said regions surrounding said first region, such that at said first area said tensile stresses resulting from the heating of said first region of maximum intensity are above the threshold for initiating or propagating cleavage in said chosen plane, but below the threshold for initiating or propagating cleavage in any other plane, thereby propagating to a new area of said plane a cleavage front separating a portion of said chosen plane where cleavage has occurred from a portion where cleavage has not yet occurred; moving said crystal or other elements, so that said region of maximum intensity is moved to a new region on said chosen plane, such that said new region has substantially the same geometrical relationship to said new area as said first region of maximum intensity had to said first area, thereby further propagating said cleavage; repeating said step of moving said crystal of other elements until cleavage has occurred at every portion of said chosen plane; and separating the part of said crystal between said flat surface and said chosen plane from the remaining part of said crystal, that excludes said part between said flat surface and said chosen plane portion, thereby creating a wafer with high quality surfaces and with no kerf loss.