Patent ID: 6560254
Filing Date: 2003-05-06
Classification: H01S

Abstract:
An excimer or molecular fluorine laser, comprising:a discharge chamber containing a laser gas mixture including a primary gas constituent composition selected from the group consisting of molecular fluorine, active argon rare gas and a buffer gas which when energized forms ArF molecules which de-excite emitting photons having wavelengths around 193 nm, molecular fluorine, active krypton rare gas and a buffer gas which when energized forms KrF molecules which de-excite emitting photons having wavelengths around 248 nm, and molecular fluorine and a buffer gas which when energized excites F2 molecules to a higher state to de-excite emitting photons having wavelengths around 157 nm; a heat exchanger and fan for circulating the gas mixture through the chamber; a pulse power circuit powered by a high voltage power supply; a plurality of electrodes within the discharge chamber and coupled to the pulse power circuit for energizing the gas mixture at a repetition rate of at least 1 kHz; a gas handling module coupled to the laser chamber for replenishing one or more components of the gas mixture; and a resonator including the chamber and line-narrowing and/or selection optics for generating a narrowband laser beam, wherein the resonator comprising said line-narrowing and/or selection optics for reducing the output emission bandwidth of the laser beam includes at least one etalon and at least one beam expanding prism, and wherein said etalon and said prism each comprise a material having an absorption coefficient of less than 5Ã—10âˆ’3/cm at 248 nm incident radiation, less than 10Ã—10âˆ’3/cm at 193 nm incident radiation, and less than 0.1/cm at 157 nm incident radiation, such that said bandwidth is reduced to less than substantially 0.6 pm, the absorption that causes heating, degrading of quality and aging of the at least one etalon and at least one beam expanding prism of said line-narrowing and/or selection optics being reduced such as to improve spectral stability of the narrowband laser beam over an operating duration of said laser, and wherein said material of said etalon and prism has a thermal conductivity greater than 2.0 W/m C, such that absorbed energy at localized regions of said at least one etalon and at least one beam expanding prism upon which the laser beam impinges diffuses away from said localized regions to less critical portions of said at least one etalon and at least one beam expanding prism at a greater rate such as to also improve spectral stability of the narrowband laser beam over the operating duration of said laser.