Most excimer beams are rectangular and have a top hat profile (flat top, steeply sloped sides) in the longer, horizontal dimension, with a near Gaussian profile in the vertical dimension. These rectangular beams are suitable for large area materials processing applications that require a certain degree of beam uniformity at the workpiece. Beam uniformity is usually described in terms of an allowable percentage variation in the energy density, or fluence, at the workpiece. This allowable variation is often referred to as the process window, which is often used to define the uniformity requirements of the excimer beam. But all excimer beams are not equal, and a beam which may be suitably uniform for one application may not be uniform enough for a different application. Thus, a knowledge of the degree of beam uniformity is very important when evaluating a laser for a given application. We have developed two beam uniformity specifications: the Top Hat Factor and Energy Fraction at 80% of peak fluence. We describe the development of these specifications and how they can be used to evaluate an excimer laser beam.

Date Published: 22 April 1993
PDF: 6 pages
Proc. SPIE 1834, Laser Energy Distribution Profiles: Measurement and Applications, (22 April 1993); doi: 10.1117/12.143846

Published in SPIE Proceedings Vol. 1834:
Laser Energy Distribution Profiles: Measurement and Applications
James M. Darchuk, Editor(s)