MY136595A - Very narrow band,two chamber, high rep rate gas discharge laser system - Google Patents

Abstract

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 5MJ OR GREATER. TWO SEPARATE DISCHARGE CHAMBERS ARE PROVIDED, ONE OF WHICH IS A PART OF A MASTER OSCILLATOR (10) PRODUCING A VERY NARROW BAND SEED BEAM WHICH IS AMPLIFIED IN THE SECOND DISCHARGE CHAMBER. THE CHAMBERS CAN BE CONTROLLED SEPARATELY PERMITTING SEPARATE OPTIMIZATION OF WAVELENGTH PARAMETERS IN THE MASTER OSCILLATOR (10) AND OPTIMIZATION OF PULSE ENERGY PARAMETERS IN THE AMPLIFYING CHAMBER (12). A PREFERRED EMBODIMENT IN AN ARF EXCIMER LASER SYSTEM CONFIGURED AS A MOPA AND SPECIFICALLY DESIGNED FOR USE AS A LIGHT SOURCE FOR INTERGRATED CIRCUIT LITHOGRAPHY. 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 0.25MILLISECONDS BETWEEN PULSES. THE MASTER OSCILLATOR (10) IS EQUIPPED WITH A LINE NARROWING PACKAGE HAVING A VERY FAST TUNING MIRROR CAPABLE OF CONTROLLING CENTERLINE WAVELENGHT ON A PULSE-TO-PULSE BASIS AT REPETITION RATES OF 4000 HZ OR GREATER TO A PRECISION OF LESS THAN 0.2 PM.