Excimer lasers are the preferred source of illumination for photolithographic systems. Lenslet array optical integrators are very frequently used to achieve good uniformity of illumination at the plane of the mask--the target to be recorded by the photolithographic system. Lenslet arrays break the incident beam up into subapertures and the resulting beams are overlapped at the plane of the target with variable incident angles. The overlapping of the tilted beams segments results in coherent interference effects leading to fine-scale intensity modulation called orange peel. We show that the ideal method of characterization of excimer lasers for this application is the Young's double hole test with hole spacing set to the lenslet element separation. This method to be superior to other common measures of laser quality such as angular divergence and M².

Date Published: 12 May 2000
PDF: 8 pages
Proc. SPIE 3930, Laser Resonators III, (12 May 2000); doi: 10.1117/12.385393

Published in SPIE Proceedings Vol. 3930:
Laser Resonators III
Alexis V. Kudryashov; Alan H. Paxton, Editor(s)