The present invention provides gas discharge laser systems capable of reliable
long-term operation in a production line capacity at repetition rates in the range
of 6,000 to 10,0000 pulses power second. Preferred embodiments are configured as
KrF, ArF and F2 lasers used for light sources for integrated circuit
lithography. Improvements include a modified high voltage power supply capable
for charging an initial capacitor of a magnetic compression pulse power system
to precise target voltages 6,000 to 10,0000 times per second and a feedback control
for monitoring pulse energy and determining the target voltages on a pulse-by-pulse
basis. Several techniques are disclosed for removing discharge created debris from
the discharge region between the laser electrodes during the intervals between
discharges. In one embodiment the width of the discharge region is reduced from
about 3 mm to about 1 mm so that a gas circulation system designed for 4,000 Hz
operation could be utilized for 10,000 Hz operation. In other embodiments the gas
flow between the electrodes is increased sufficiently to permit 10,000 Hz operation
with a discharge region width of 3 mm. To provide these substantial increased gas
flow rates, Applicants have disclosed preferred embodiments utilize tangential
forms of the prior art but with improved and more powerful motors and novel bearing
designs. New bearing designs include both ceramic bearings and magnetic bearings.
In other embodiments, some or all of the gas circulation power is provided with
a blower located outside the laser chamber. The outside blower can be located in
the laser cabinet or in separate location.
