Laser beam homogenization by scanning a beam onto a mask

Abstract

Apparatus that homogenizes a laser beam, in applications where multiple laser pulses are used to drill holes in a work piece by projecting an image of a mask onto the work piece, scans the laser beam across the mask to achieve substantially equal laser fluence through each opening in the mask. Any non-uniform beam illumination is averaged out during the multiple pulse drilling process. One embodiment of the invention uses a mirror mounted on a motor such that the reflecting surface of the mirror is at an angle to a plane which is perpendicular to the axis of rotation of the motor. This embodiment traces a circular path on the mask. Another embodiment of the invention employs two galvo mirrors to scan the laser beam. The first galvo mirror is configured to reflect the laser beam on to the second galvo mirror and the second galvo mirror is configured to reflect the laser beam onto the mask, wherein each of the first and second galvo mirrors rotates about a rotational axis in the plane of its mirror. By mounting the galvo mirrors to have orthogonal axes of rotation, this apparatus can trace the laser beam in an arbitrary pattern across the mask.

Dependencies are inferred from the claim text.