Radiant energy – Invisible radiant energy responsive electric signalling – Ultraviolet light responsive means
Reexamination Certificate
1999-12-03
2002-05-28
Dang, Hung Xuan (Department: 2873)
Radiant energy
Invisible radiant energy responsive electric signalling
Ultraviolet light responsive means
C250S330000
Reexamination Certificate
active
06396062
ABSTRACT:
BACKGROUND OF THE INVENTION
One characteristic of deep ultraviolet lasers which is of great importance for success in lithography system usage is the optical intensity profile of the laser beam, called the beam profile here. A beam profile mathematically or pictorially defines the shape of the laser beam in terms of intensity at some defined axial position which may be anywhere within the optical resonator cavity of the laser, or anywhere along the output beam which is considered to start at the output coupler (OC). The standard approach to obtain deep ultraviolet (DUV) beam profiles for many years requires a lab setup with massive high stability optical tables, but the commercial users of the lasers will almost never have access to bulky lab equipment in integrated circuit fabrication plants. As a result, it is typical to run an installed laser to end of life with no beam profile data beyond the initial factory certification data of the laser when it was brand new. Profiles of a laser beam differ along the path of the beam. Knowledge of the profile at various positions along the path can be very valuable when aligning the laser for optimum performance.
What is needed is a portable device for field measurement of laser beam profiles.
SUMMARY OF THE INVENTION
The present invention provides a portable laser beam monitor utilizes a plurality of optical trains to monitor ultraviolet laser beam profiles at a plurality of positions along a laser beam path. A preferred embodiment useful for monitoring beam profiles of lithography lasers measures the beam profile at the front aperture, the rear aperture, the shutter plane and at infinity (the divergence plane). The beam profiles are imaged on a fluorescent screen which is monitored by a visible light camera. Images of the profiles may be discharged on the screen of a lap top computer.
REFERENCES:
patent: 5745268 (1998-04-01), Eastvold et al.
Buck Jesse D.
Ozarski Robert G.
Cymer Inc.
Ross, Esq. John R.
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