Two chamber F2 laser system with F2 pressure based line selection
First Claim
1. A very narrow band two chamber high repetition rate F2 gas discharge laser system comprising:
- A) a first laser unit comprising;
1) a first discharge chamber containing;
a) a first laser gas comprising fluorine gas defining a fluorine partial pressure and at least one buffer gas wherein said laser gas defines a total gas pressure b) a first pair of elongated spaced apart electrodes defining a first discharge region, 2) a first fan for producing sufficient gas velocities of said first laser gas in said first discharge region to clear from said first discharge region, following each pulse, substantially all discharge produced ions prior to a next pulse when operating at a repetition rate in the range of 2,000 pulses per second or greater, 3) a first heat exchanger system capable of removing at least 16 kw of heat energy from said first laser gas, B) a second laser unit comprising;
1) a second discharge chamber containing;
a) a second laser gas, b) a second pair of elongated spaced apart electrodes defining a second discharge region 2) a second fan for producing sufficient gas velocities of said second laser gas in said second discharge region to clear from said second discharge region, following each pulse, substantially all discharge produced ions prior to a next pulse when operating at a repetition rate in the range of 4,000 pulses per second or greater, 3) a second heat exchanger system capable of removing at least 16 kw of heat energy from said second laser gas, C) a pulse power system configured to provide electrical pulses to said first pair of electrodes and to said second pair of electrodes sufficient to produce laser pulses at rates of about 4,000 pulses per second with precisely controlled pulse energies in excess of about 5 mJ, D) a laser beam measurement and control system for measuring pulse energy of laser system output pulses produced by said two chamber laser system and controlling said laser output pulses in a feedback control arrangement, and wherein output laser beams from said first laser unit are utilized as a seed beam for seeding said second laser unit and wherein said fluorine partial pressure in said first chamber and said total gas pressure is said first chamber are low enough that spectral intensity of the laser system output pulses at about 157.52 nm is less than 0.5% of spectral intensity of the laser system output pulses at 157.63 nm.
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Accused Products
Abstract
The present invention provides an injection seeded modular gas discharge laser system capable of producing high quality pulsed laser beams at pulse rates of about 4,000 Hz or greater and at pulse energies of about 5 to 10 mJ or greater for integrated outputs of about 20 to 40 Watts or greater. Two separate discharge chambers are provided, one of which is a part of a master oscillator producing a very narrow band seed beam which is amplified in the second discharge chamber. The parameters chamber can be controlled separately permitting optimization of wavelength parameters in the master oscillator and optimization of pulse energy parameters in the amplifying chamber. A preferred embodiment is a F2 laser system configured as a MOPA and specifically designed for use as a light source for integrated circuit lithography. In this preferred embodiment, both of the chambers and the laser optics are mounted on a vertical optical table within a laser enclosure. In the preferred MOPA embodiment, each chamber comprises a single tangential fan providing sufficient gas flow to permit operation at pulse rates of 4000 Hz or greater by clearing debris from the discharge region in less time than the approximately 0.25 milliseconds between pulses. The master oscillator is operated with a fluorine partial pressure and total gas pressure within specified ranges in order to reduce the intensity of the weak line to less than 0.01% of the strong line. Therefore, the need for line selection optical equipment is avoided.
54 Citations
64 Claims
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1. A very narrow band two chamber high repetition rate F2 gas discharge laser system comprising:
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A) a first laser unit comprising;
1) a first discharge chamber containing;
a) a first laser gas comprising fluorine gas defining a fluorine partial pressure and at least one buffer gas wherein said laser gas defines a total gas pressure b) a first pair of elongated spaced apart electrodes defining a first discharge region, 2) a first fan for producing sufficient gas velocities of said first laser gas in said first discharge region to clear from said first discharge region, following each pulse, substantially all discharge produced ions prior to a next pulse when operating at a repetition rate in the range of 2,000 pulses per second or greater, 3) a first heat exchanger system capable of removing at least 16 kw of heat energy from said first laser gas, B) a second laser unit comprising;
1) a second discharge chamber containing;
a) a second laser gas, b) a second pair of elongated spaced apart electrodes defining a second discharge region 2) a second fan for producing sufficient gas velocities of said second laser gas in said second discharge region to clear from said second discharge region, following each pulse, substantially all discharge produced ions prior to a next pulse when operating at a repetition rate in the range of 4,000 pulses per second or greater, 3) a second heat exchanger system capable of removing at least 16 kw of heat energy from said second laser gas, C) a pulse power system configured to provide electrical pulses to said first pair of electrodes and to said second pair of electrodes sufficient to produce laser pulses at rates of about 4,000 pulses per second with precisely controlled pulse energies in excess of about 5 mJ, D) a laser beam measurement and control system for measuring pulse energy of laser system output pulses produced by said two chamber laser system and controlling said laser output pulses in a feedback control arrangement, and wherein output laser beams from said first laser unit are utilized as a seed beam for seeding said second laser unit and wherein said fluorine partial pressure in said first chamber and said total gas pressure is said first chamber are low enough that spectral intensity of the laser system output pulses at about 157.52 nm is less than 0.5% of spectral intensity of the laser system output pulses at 157.63 nm. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64)
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Specification