Reliable, modular, production quality narrow-band high rep rate F2 laser

Abstract

The present invention provides a reliable modular production quality excimer laser capable of producing 10 mJ laser pulses in the range of 1000 Hz to 2000 Hz or greater. Replaceable modules include a laser chamber; a pulse power system comprised of three modules; an optical resonator comprised of a line narrowing module and an output coupler module; a wavemeter module, an electrical control module, a cooling water module and a gas control module. Important improvements have been provided in the pulse power unit to produce faster rise time and improved pulse energy control. These improvements include an increased capacity high voltage power supply with a voltage bleed-down circuit for precise voltage trimming, an improved communication module that generates a high voltage pulse from the capacitors charged by the high voltage power supply and amplifies the pulse voltage 23 times with a very fast voltage transformer having a secondary winding consisting of a single four-segment stainless steel rod. A novel design for the compression head saturable inductor greatly reduces the quantity of transformer oil required and virtually eliminates the possibility of oil leakage which in the past has posed a hazard.

Description

BACKGROUND OF THE INVENTIONKrF Excimer LasersKrypton-Fluoride (KrF) excimer lasers are currently becoming the workhorse light source for the integrated circuit lithography industry. The KrF laser produces a laser beam having a narrow-band wavelength of about 248 nm and can be used to produce integrated circuits with dimensions as small as about 180 nm. The Argon Fluoride (ArF) excimer laser is very similar to the KrF laser. The primary difference is the laser gas mixture and a shorter wavelength of the output beam. Basically, Argon replaces Krypton and the resulting wavelength of the output beam is 193 nm. This permits the integrated circuit dimensions to be further reduced to about 120 nm. F.sub.2 lasers have long been recognized as the successor to the KrF and ArF lasers in the integrated circuit lithography industry since the F.sub.2 beam at 157 nm permits a substantial improvement in pattern resolution. These F.sub.2 lasers can be very similar to the KrF and ArF excimer lasers a...

AI Technical Summary

Benefits of technology

The present invention provides a reliable, modular, production quality F.sub.2 excimer laser capable of producing, at repetition rates in the range of 1,000 to 2,000 Hz or greater, laser pulses with pulse energies greater than 10 mJ with a full width half, maximum bandwidth of about 1 or less. Preferred embodiments of the present invention can be operated in the range of 1000 to 4000 Hz with pulse energies in the range of 10 to 5 mJ with power outputs in the range of 10 to 40 watts. Using this laser as an illumination source, stepper or scanner equipment can produce integrated circuit resolution of 0.1 .mu.m or less. Replaceable modules include a laser chamber and a modular pulse power system.

Improvements in the laser chamber permitting the higher pulse rates and improved performance include the use of a single preionizer tube.

Other embodiments of the present invention include ceramic bearings. Optionally magnetic bearings may be utilized. Reaction forces on the bearings may be reduced by providing an aerodynamic contour on the anode support bar. Other improvements include use of acoustic baffles for laser chambers producing disruptive acoustic shock waves.

Problems solved by technology

In prior art systems, this feedback signal is an analog signal and it is subject to noise produced by the laser environment.

This noise can result in erroneous power supply voltages being provided and can in turn result in increased variation in the output laser pulse energy.

One problem experienced with these prior-art lasers has been excessive wear and occasional failure of blower bearings.

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