| Popis: |
Commercially used lithography lasers are line narrowed KrF excimer lasers (Ref. 1) operated at (248.38 0.2) nm at 2 W (10 mJ, 200 Hz) with a bandwidth of typically 3 pm (Ref.2). A system control concept for alternative control at two different locations including a remote RS 232 C operation has been developed. The on-line controlled parameters are: pulse energy, absolute wavelength, bandwidth and maintenance requests. Two years field experience with Lambda 248 L excimer lasers and long term test results are summarized. Lifetime issues and scheduled service actions are also presented. The 4 W Lambda 248 L-400 excimer laser was operated with modified optics, which led to an integral bandwidth below 2 pm. A narrower bandwidth provides the advantage of producing smaller feature sizes, e.g., 0.4 tm even with higher numerical aperture lenses. Bandwidth measurements and methods are compared. Lineshape measurements and corresponding energy portions were calculated to describe the spectral distribution. Long-term bandwidth monitoring results (over 8 hours continuous operation, burst mode operation) are described. Furthermore the high rep.-rate 248 L-400 laser was evaluated relative to pulse energy, bandwidth and pulse to pulse energy fluctuations. A maximum average power of more than 1 1 W (400 Hz, 28 nil) was achieved. Stabilized operation at 15 mJ, 400 Hz over several hours was demonstrated. The experimental results are presented and discussed. |
