Method for separating a workpiece
A method for separating a workpiece along a separation line by using laser pulses of a laser beam includes splitting the laser beam into a plurality of partial laser beams using a beam splitter optical unit, focusing the plurality of partial laser beams onto a surface of the workpiece and/or into a volume of the workpiece using a focusing optical unit, so that the plurality of partial laser beams are arranged next to one another and spaced apart from one another along the separation line, and ablating material of the workpiece along the separation line by introducing the laser pulses of the plurality of partial laser beams into the workpiece. The laser power per partial laser beam is adjusted depending on an ablation depth obtained in the workpiece.
1 . A method for separating a workpiece along a separation line by using laser pulses of a laser beam, the method comprising:
splitting the laser beam into a plurality of partial laser beams using a beam splitter optical unit,
focusing the plurality of partial laser beams onto a surface of the workpiece and/or into a volume of the workpiece using a focusing optical unit, so that the plurality of partial laser beams are arranged next to one another and spaced apart from one another along the separation line, and
ablating material of the workpiece along the separation line by introducing the laser pulses of the plurality of partial laser beams into the workpiece, wherein the laser pulses traverse along the separation line multiple times, wherein the laser power per partial laser beam is adjusted for different traversals along the separation line depending on an ablation depth obtained in the workpiece.
2 . The method as claimed in claim 1 , wherein the laser power per partial laser beam is adjusted by adjusting a number of partial laser beams for a given input power of the laser beam, with the number of partial laser beams being reduced with increasing ablation depth.
3 . The method as claimed in claim 1 , wherein the laser power per partial laser beam is increased with increasing ablation depth.
4 . The method as claimed in claim 1 , wherein the beam splitter optical unit comprises a plurality of microlens arrays.
5 . The method as claimed in claim 4 , wherein the beam splitter optical unit comprises at least two microlens array pairs, wherein each microlens array pair comprises two microlens arrays, the two microlens arrays of a microlens array pair having a fixed distance from one another.
6 . The method as claimed in claim 5 , wherein the laser power per partial laser beam and/or a number of partial laser beams is adjusted by displacing the two microlens array pairs relative to one another.
7 . The method as claimed in claim 4 , wherein one microlens array or one microlens array pair of the plurality of microlens arrays comprises convex microlenses.
8 . The method as claimed in claim 1 , wherein the partial laser beams are focused into a same focal plane.
9 . The method as claimed in claim 1 , wherein the partial laser beams are moved away from an original position along the separation line by a deflection value, the movement being correlated with a repetition rate of the laser beam so as to ensure uniform material ablation.
10 . The method as claimed in claim 9 , wherein the deflection value is less than or equal to a distance between two adjacent partial laser beams, and the partial laser beams are subsequently moved back into the original position along the separation line, the movement being a periodic movement.
11 . The method as claimed in claim 9 , wherein the separation line is straight and the movement of the partial laser beams is a linear deflection.
12 . The method as claimed in claim 10 , wherein the periodic movement is generated by a periodic movement of the focusing optical unit.
13 . The method as claimed in claim 1 , wherein the laser pulses are ultrashort laser pulses.
14 . The method as claimed in claim 1 , wherein the partial laser beams and the workpiece are capable of being displaced relative to one another, with a feed along a feed direction.
15 . The method as claimed in claim 1 , further comprising decomposing the laser beam and/or the partial laser beams into two mutually orthogonal polarization components by passing the laser beam and/or the partial laser beams through a birefringent polarizer element.
16 . The method as claimed in claim 15 , wherein the two mutually orthogonal polarization components have an angular offset and/or spatial offset with respect to one another.
17 . The method as claimed in claim 16 , wherein the focused partial laser beams have an alternating polarization along the separation line, or the polarization of each partial laser beam is aligned along the separation line or orthogonal to the separation line.
18 . The method as claimed in claim 16 , wherein the overall separation process is divided into various partial separation processes, with each partial process being carried out either with p-polarized partial laser beams or s-polarized partial laser beams.
19 . The method as claimed in claim 1 , wherein the workpiece comprises a silicon wafer.