Utilisation of scattered light for excimer laser beam monitoring

✍ Scribed by A. Hermann; A. Kaemling; F. Ach; C. Fischer; W. Viöl

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 183 KB
• Volume: 2
• Category: Article
• ISSN: 1612-2011
• DOI: 10.1002/lapl.200510021

✦ Synopsis

The investigated new online beam monitoring system is
based on the detection of scattered light emitted from a
deflecting mirror in a UV laser beam guidance system. The
scattered light from the mirror is projected on a detector and the
captured data is evaluated by a software. The deflecting
dielectric mirrors used as scattered light source were analysed
with noncontact AFM measurements to predict the expected scattered
light intensity. To test the quality of the measurement technique,
the profiles detected by scattered light were compared with
directly captured profiles. The investigated laser systems emit
wavelengths in the VUV/DUV domain: the fluorine laser at
λ=157 nm, the argon fluoride laser at λ=193 nm,
and the krypton fluoride laser at λ=248 nm. One of the big
advantages of this beam monitoring system is that the laser beam
remains unaffected by the measurement. The system is also capable
of localising the beam and detecting power fluctuations in real
time with high temporal and spacial resolution. An online
measurement during a machining process is therefore possible.