# US 8,569,650 B2 · Laser material removal methods and apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,569,650 B2 - Document ID: US8569650B2 - Status: Granted - Kind: B2 - Application number: 13/565,455 - Filed: 2012-08-02 - Published: 2012-11-22 - Granted: 2013-10-29 - Earliest claimed: 2008-08-26 - Assignees: Applied Materials, Inc. - Applicants: Zhenhua Zhang; Virendra V. S. Rana; Vinay K. Shah; Chris Eberspacher - Inventors: Zhenhua Zhang; Virendra V. S. Rana; Vinay K. Shah; Chris Eberspacher - Web page: https://patentgrep.com/patent/US8569650B2 ## CPC - B23K 26/03: Observing, e.g. monitoring, the workpiece - B23K 26/06: Shaping the laser beam, e.g. by masks or multi-focusing - B23K 26/0624: {using ultrashort pulses, i.e. pulses of 1 ns or less} - B23K 26/082: Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head - B23K 26/0853: {Devices involving movement of the workpiece in at least two axial directions, e.g. in a plane} - B23K 26/364: for making a groove or trench, e.g. for scribing a break initiation groove - B23K 26/40: taking account of the properties of the material involved - H10F 10/146: {Back-junction photovoltaic cells, e.g. having interdigitated base-emitter regions on the back side} - H10F 71/00: Manufacture or treatment of devices covered by this subclass (patterning processes to connect thin photovoltaic cells in integrated devices, or assemblies of multiple devices, having photovoltaic cells H10F19/33; manufacture or treatment of encapsulations or containers for integrated devices, or assemblies of multiple devices, having photovoltaic cells H10F19/80; manufacture or treatment of integrated devices, or assemblies of multiple devices, comprising at least one element in which radiation controls the flow of current H10F39/00) - H10F 77/219: {Arrangements for electrodes of back-contact photovoltaic cells} - B23K 2101/40: Semiconductor devices - B23K 2103/50: {Inorganic materials other than metals or composite materials} - Y02E 10/547: Monocrystalline silicon PV cells - B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract Embodiments of the present invention generally provide methods and apparatus for material removal using lasers in the fabrication of solar cells. In one embodiment, an apparatus is provided that removes portions of a dielectric layer deposited on a solar cell substrate according to a desired pattern. In certain embodiments, methods for removing a portion of a material via a laser without damaging the underlying substrate are provided. In one embodiment, the intensity profile of the beam is adjusted so that the difference between the maximum and minimum intensity within a spot formed on a substrate surface is reduced to an optimum range. In one example, the substrate is positioned such that the peak intensity at the center versus the periphery of the substrate is lowered. In one embodiment, the pulse energy is improved to provide thermal stress and physical lift-off of a desired portion of a dielectric layer. ## Claims ### Claim 1 A method of laser material removal, comprising: thermally stressing a region of dielectric material deposited on a substrate by positioning the substrate out of focus of a light emitted from a laser such that a portion of the light strikes the dielectric material above an ablation threshold of the dielectric material and strikes the substrate beneath an ablation threshold of the substrate to remove the dielectric material from the region without damaging the substrate. ### Claim 2 (depends on 1) The method of claim 1, wherein the removing the dielectric material comprises ablating the dielectric material without damaging the substrate. ### Claim 3 (depends on 1) The method of claim 1, wherein the thermally stressing the region of dielectric material comprises setting parameters of the laser such that a portion of light emitted from the laser strikes the dielectric material above an ablation threshold of the dielectric material and strikes the substrate beneath an ablation threshold of the substrate. ### Claim 4 (depends on 3) The method of claim 3, wherein the removing the dielectric material comprises ablating the dielectric material without damaging the substrate. ### Claim 5 (depends on 1) The method of claim 1, wherein the removing the dielectric material comprises physically removing the dielectric material without ablating the dielectric material. ### Claim 6 (depends on 1) The method of claim 1, wherein the dielectric material is adjacent the substrate. ### Claim 7 (depends on 1) The method of claim 1, wherein the substrate is a silicon substrate. ### Claim 8 (depends on 7) The method of claim 7, wherein the dielectric material is silicon oxide. ### Claim 9 A method for processing a substrate, comprising: depositing a dielectric material on a surface of a silicon substrate; thermally stressing a portion of the dielectric material in a desired pattern by positioning the silicon substrate out of focus of a light emitted from a laser such that a portion of the light strikes the dielectric material above an ablation threshold of the dielectric material and strikes the silicon substrate beneath an ablation threshold of the silicon substrate to remove the dielectric material from the portion of the dielectric material in the desired pattern without damaging the silicon substrate. ### Claim 10 (depends on 9) The method of claim 9, wherein the removing the dielectric material comprises ablating the dielectric material without damaging the silicon substrate. ### Claim 11 (depends on 9) The method of claim 9, wherein the thermally stressing the portion of the dielectric material comprises setting parameters of the laser such that a portion of light emitted from the laser strikes the dielectric material above an ablation threshold of the dielectric material and strikes the silicon substrate beneath an ablation threshold of the silicon substrate. ### Claim 12 (depends on 11) The method of claim 11, wherein the removing the dielectric material comprises ablating the dielectric material without damaging the silicon substrate. ### Claim 13 (depends on 9) The method of claim 9, wherein the removing the dielectric material comprises physically removing the dielectric material without ablating the dielectric material. ### Claim 14 (depends on 9) The method of claim 9, wherein the dielectric material is silicon oxide. ### Claim 15 A method of laser material removal, comprising: emitting a light from a laser source to form a light spot on a region of a dielectric material deposited on a substrate, wherein a peak intensity at the center of the light spot is relatively higher than a peripheral intensity along the periphery of the light spot; and thermally stressing the region of the dielectric material within the light spot by positioning the substrate out of focus of the light such that a portion of the light strikes the dielectric material above an ablation threshold of the dielectric material and strikes the substrate beneath an ablation threshold of the substrate to remove the dielectric material from the region without damaging the substrate.