Patent DE-102008026792-A1 (DE)
Title: Apparatus for laser-machining substrate such as copper indium diselenide-thin film solar cell elements arranged in machining area, comprises laser operable in pulsed mode, beam distribution unit, machining units, and beam expansion optic
Inventor: GRUNDMUELLER RICHARD
IPC: H01L21/302
Filed: 2008-06-04
Abstract: The apparatus comprises a laser (1) operable in a pulsed mode, a beam distribution unit arranged in a beam path after the laser for distributing a laser beam (1a) from the laser into several partial beams or provided for laser for generating several partial beams, machining units disposed in a beam path, and a beam expansion optic for expanding the average beam diameter of the laser beam. The machining units have an aperture diaphragm (2) arranged and designed in the beam path of the laser, so that the partial laser beam produced and/or producible from the laser is cut in its edge region. The apparatus comprises a laser (1) operable in a pulsed mode, a beam distribution unit arranged in a beam path after the laser for distributing a laser beam (1a) from the laser into several partial beams or provided for laser for generating several partial beams, machining units disposed in a beam path, and a beam expansion optic for expanding the average beam diameter of the laser beam. The machining units have an aperture diaphragm (2) arranged and designed in the beam path of the laser, so that the partial laser beam produced and/or producible from the laser is cut and/or cuttable in its edge region in a section-wise manner, a deflection unit (3), which is arranged in the beam path after the aperture diaphragm and comprises ten deflectors arranged one after the other in the beam path for deflecting the cut laser beam, and a focusing unit (4) arranged in the beam path after the deflection unit and formed in a machining area for reducing and focusing the image of the aperture diaphragm. The aperture diaphragm, the deflection unit and the focusing unit of the machining units are disposed in a separate housing. The apparatus includes a deflection mirror as a deflection device stationarily and non-rotatably arranged in relation to its deflection unit, and a transport device formed for transporting a substrate through the machining area. The beam expansion optic is arranged in the beam path after the laser and before the aperture diaphragm. The ratio (V=D(L) / D(A)) of an average beam diameter D(L) of the laser beam to the height of the aperture diaphragm and average aperture diameter D(A) of the aperture diaphragm is >= 3. The aperture diaphragm and the laser are designed, so that the aperture diaphragm cuts off the beam parts of the laser beam in laser operated in the basic mode of TEM 00, where the beam parts of the laser beam lies outside of the point of the radial distribution l(r) of the radiant power, at which the radiant power is fallen off to 85% of the maximal value l max. The deflection unit, through which the deflectors are arranged one after the other in the beam path, realizes a beam path length (g) between the aperture diaphragm and the focusing unit, where the beam path length is larger than the beam path length (b) between the focusing unit and the focused image of the aperture diaphragm in the machining area by a factor of 30. The reduction factor G/B of the aperture diaphragm (G) and the aperture diaphragm image (B) is 30. The deflectors are arranged and disposed, so that a meander-like beam path of the laser beam and/or a multiple deflection of the laser beam is realizable and/or realized at 90[deg] in the deflection unit. A circular, quadratic, rectangular or diamond-shaped aperture is present in the aperture diaphragm. Two of the four edges of the quadratic or rectangular aperture have a distortion or a bulge directed towards and outwardly viewed from the midpoint of the aperture and/or the quadratic or rectangular aperture is smaller at its periphery of two in the cross-section and the quadratic or rectangular peripheral aperture is flanked in the aperture diaphragm. Two edges of the quadratic or rectangular aperture that are rectangularly or quadratically adjacent to same side edges of the aperture have distortion or bulge in the form of cushion-shaped distortion on one-side or are flanked by respective peripheral aperture and/or all the four edges of the quadratic or rectangular aperture have the distortion or bulge in the form of cushion-shaped distortion or are flanked by respective peripheral aperture. The machining units are disposed and designed, so that the focusing units of the machining units focus the aperture diaphragm of the partial beam paths at different positions lying in a line in the machining area. An independent claim is included for a method for laser-machining a substrate e.g. a thin film solar cell element arrangeable and/or arranged in a machining area.