Four KHz gas discharge laser system
First Claim
1. An extreme repetition rate gas discharge laser system capable of operating at pulse repetition rates in excess of 3,000 laser output pulses per second, said laser comprising:
- A) a laser chamber containing a laser gas and having two elongated electrodes, defining a discharge region and having a gas flow path with a gradually increasing cross section downstream of said electrodes to permit recovery of a large percentage of static pressure drop occurring in the discharge region, B) a tangential type fan for producing sufficient gas movement said laser gas in said discharge region to clear from said discharge region, following each gas discharge in said discharge region, substantially all discharge produced ions prior to a next gas discharge when operating at a repetition rate up to and above 4,000 gas discharge per second or greater, C) a heat exchanger system removing heat energy from said laser gas, D) a pulse power system provide electrical pulses to said electrodes sufficient to produce laser output pulses at rates of up to and above 4,000 laser output pulses per second with precisely controlled pulse energies in the range of about 5 mJ, and E) a laser beam measurement and control system measuring pulse energy wavelength and bandwidth of every pulse or substantially every pulse with feedback control of laser output pulse energy and wavelength.
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Accused Products
Abstract
The present invention provides an excimer laser capable of producing a high quality pulsed laser beam at pulse rates of about 4,000 Hz at pulse energies of about 5 mJ or greater. A preferred embodiment is an ArF excimer laser specifically designed as a light source for integrated circuit lithography. An improved wavemeter with special software monitors output beam parameters and controls a very fast PZT driven tuning mirror and the pulse power charging voltage to maintain wavelength and pulse energy within desired limits. In a preferred embodiment two fan motors drive a single tangential fan which provides sufficient gas flow to clear discharge debris from the discharge region during the approximately 0.25 milliseconds between pulses.
55 Citations
66 Claims
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1. An extreme repetition rate gas discharge laser system capable of operating at pulse repetition rates in excess of 3,000 laser output pulses per second, said laser comprising:
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A) a laser chamber containing a laser gas and having two elongated electrodes, defining a discharge region and having a gas flow path with a gradually increasing cross section downstream of said electrodes to permit recovery of a large percentage of static pressure drop occurring in the discharge region, B) a tangential type fan for producing sufficient gas movement said laser gas in said discharge region to clear from said discharge region, following each gas discharge in said discharge region, substantially all discharge produced ions prior to a next gas discharge when operating at a repetition rate up to and above 4,000 gas discharge per second or greater, C) a heat exchanger system removing heat energy from said laser gas, D) a pulse power system provide electrical pulses to said electrodes sufficient to produce laser output pulses at rates of up to and above 4,000 laser output pulses per second with precisely controlled pulse energies in the range of about 5 mJ, and E) a laser beam measurement and control system measuring pulse energy wavelength and bandwidth of every pulse or substantially every pulse with feedback control of laser output pulse energy and wavelength. - 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)
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47. A gas discharge laser system comprising:
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A) a laser chamber containing a laser gas and having two elongated electrodes, defining a discharge region therebetween and having a gas flow path through the discharge region, B) a fan for producing sufficient gas movement of said laser gas through said discharge region to clear from said discharge region, following each gas discharge in said discharge region, substantially all discharge produced ions prior to a next gas discharge when operating at a repetition rate of up to and above 4,000 gas discharges per second, C) a heat exchanger system removing heat energy from said laser gas, D) a pulse power system providing electrical pulses to said electrodes sufficient to produce laser output pulses at rates of up to and above 4,000 laser output pulses per second with precisely controlled pulse energies, and E) a laser beam measurement and control system measuring pulse energy, wavelength and bandwidth of every pulse or substantially every pulse with feedback control of the laser output, said laser beam measurement and control system comprising a fringe producing optic, a fringe photo detector producing output signals representative of a fringe pattern, a programmable logic device receiving the output signals of the fringe photo detector, and having logic that analyzes the output signals of the fringe photo detector to determine the presence and location of the fringes and provide an output signal representative of the presence and location of the fringes. - View Dependent Claims (48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66)
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Specification