Long pulse ArF and F_2 excimer lasers

摘要

For some specific application areas like (V)UV lithography or special processing of certain materials with high average power (V)UV lasers excimer lasers have to be developed further. In this contribution we will summarise the recent progress of our VUV excimer laser programme on the ARF and F_2 laser. Key point in our research programme is the production of long laser pulses in the order of 100 ns (FWHM). An existing laser chamber was modified and optimised for the ArF laser research programme. Different excitation circuits have been tested. For long pulse operation the laser is operated in the ferrite switched resonant overshoot mode using 18 cm~2 of ferrite in the switch for a discharge volume of approximately 60 x 0, 7 x 1,2 cm~3. Long optical pulses of up to 116 ns have been obtained with a lean gas mixture and a very low self-inductance of the electrical circuit of the packing capacitors. For the F_2 laser a new discharge chamber and a new X-ray preionisation source was designed. With this set-up it was possible to produce a F_2 laser with a large optical cross-section of 1,5 x 2,4 cm~2 operating at an intrinsic efficiency of 0,1percent. With a different electrical circuit the system produced long optical utput pulses of 70 ns (FWHM) in a gas mixture of helium and 3 mbar F_2 at a total gas pressure of 2 bar.