Advanced ArF excimer laser for 193 nm lithography

The ArF excimer laser light source will extend the optical lithography to below 0.18 mu m design rules. Still under discussion is the most efficient layout of the stepper or scanner imaging optics, which has great impact on the laser-bandwidth requirements. Cost effective operation of a stepper or scanner tool requires a 193 nm excimer laser with high power and repetition rates in the order of 1 kHz or higher. Precise dose control of the exposure demands a high repetition rate and excellent stability of the laser output energy. We have developed an ArF laser which can be operated with up to 800 Hz repetition rate based on NovaTube(TM) technology. Optimized materials and discharge configurations have been used to achieve laser tube lifetimes above 10(9) pulses. Up to 4 x 10(9) pulses tube lifetimes have been reported in beta-site tests. Gas lifetime of several 10(7) laser pulses is obtained. A solid-state switch has been adapted for the reliable and cost efficient operation of the 193 nm lithography laser. To achieve laser output of different bandwidths various resonator arrangements have been investigated. The paper gives an overview of the currently achievable power levels at different bandwidths and discusses future trends.