Peter Heist

Measurement of ultraviolet femtosecond pulses using the optical kerr effect

We demonstrate the optical Kerr shutter technique as a simple and powerful tool for the measurement of femtosecond pulses in the ultraviolet as well as in the visible spectral region. The method provides the third-order intensity correlation function which gives information about pulse asymmetry and pulse structures.

Ultrafast beam-deflection method and its application for measuring the transient refractive index of materials

We represent an ultrafast beam-deflection method as a simple and powerful tool for the time-resolved measurement of induced changes of the refractive index in the order of Δn=10−5. The method is applied for measuring the changes of components of the refractive index parallel and perpendicular to the pump-pulse polarization on a femtosecond time scale. Fused silica and CS2 are used as samples for demonstrating our method.

ArF excimer laser for 193-nm lithography

The ArF excimer laser light source will extend the optical lithography to below 0.18 micrometers design rules. Still under discussion is the most effective layout of the stepper or scanner imaging optics. The decision for an all-fused-silica lens, an achromatic lens using CaF2, or a catadioptric imaging system has great impact on the laser-bandwidth requirement. In addition, the potential performance and perspective of the laser must be considered in the system layout of the production stepper or step and scan tool. Cost effective operation of such a lithography 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 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 NovaTubeTM technology. Optimized materials and discharge configurations have been used to achieve laser tube lifetimes above 109 pulses. Up to 4 X 109 pulses tube lifetime have been achieved in beta-site tests. Gas lifetime of several 107 laser pulses is obtained. A solid-state switch has been adapted for the reliable and cost efficient excitation 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.

Extremely narrow-bandwidth high-repetition-rate laser for high-NA step-and-scan tools

In this paper we discuss several resonator designs in terms of bandwidth, efficiency and lifetime of the major optical components. Experimental data are presented for a resonator combining the advantages of a long lifetime grating and etalon elements. Moreover, the limitations of these elements are overcome through the outcoupling scheme, ensuring optimum feedback over gas and tube lifetimes. In addition to low cost-of-ownership, this same resonator provides for an extremely narrow bandwidth ArF excimer laser development, using a single oscillator.