ELECTRIC DISCHARGE LASER WITH ACOUSTIC CHIRP CORRECTION

摘要

The invention incorporates methods and structural changes in gas discharge lasers for minimizing wavelength chirp at high pulse rates. The major cause of wavelength chirp in high pulse rate gas discharge lithography lasers as pressure waves from a discharge reflecting back to the discharge region coincident with a subsequent discharge. During burst mode operation, the laser gas temperature in prior art lasers changes. This in turn changes the location of the coincident pressure waves from pulse to pulse, which ultimately alters the beam direction, causing the grating in the LNP to reflect back to the discharge region light at a slightly different wavelength. A solution to the problem is to include in the laser chamber structural elements to moderate or disperse the pressure waves and to maintain a constant laser gas temperature. One embodiment has a laser gas discharge chamber with baffles (70), heat exchanger (40), and a fan (38).