Study Of Key Technologies Of High Repetition Rate ArF Excimer Laser

The development history and the application in scientific research,medical and industry of excimer laser are summarized and the recent progress of the development of high repetition rate excimer laser at home and abroad is introduced.The key technologies involved in the design of high repetition rate excimer laser chamber,such as discharge electrode and corona preionization technology,high-speed circulation technology,acoustic wave dissipating technology,heat exchange technology and so on are put forward.The practical examples of the key technologies are described and analyzed to provide the design points of 4 kHz repetition rate ArF excimer laser chamber.Based on the design theory of Chang electrode,a pair of compact Chang electrodes for high-repetition-rate discharge is designed.The initial electron concentration provided to the discharge of the main electrode is created by corona preionization.Through the suitable design of cross-flow fan,magnetic coupler and gas flow circuit,the average gas flow velocity above 33.3 m/s is achieved in the discharge area.The flow field is numerically calculated and the gas flow in the laser chamber is visually observed.The simulation and experimental results show that the magnitude and uniformity of the gas flow velocities in the discharge region are suitable for discharge.Through the cooling system,over 8.2 kW thermal powers in laser chamber are taken away by cooling water.Suitable heat exchange structure can adapt to expansion and contraction.Double O-rings seal structure is designed to achieve reliable isolation between working gas and cooling water.The compact design of the confluence structure makes the cooling system of the laser only having a water inlet and a water outlet,and the complicated pipeline connection is avoided.An ArF excimer laser operating at the repetition rate of 4 kHz is designed,fabricated and assembled for experiment.The experiment study of discharge in high-repetition-rate ArF excimer laser is carried out.Through the optimization of the structure of the preionization structure,the problem of creepage on the surface of ceramic tube and the problem of arcing in the outlet of discharge area are solved.With the DC power supply voltage 750 V,the highest repetition rate of ArF excimer laser could operate at 4500 Hz.When operating at the repetition rate of 4 kHz and the discharge voltage of 17.4 kV,the maximum output power of ArF excimer laser measured by spectrophotometer is about 72 W,Energy stability is better than 1.5%and the conversion efficiency between electricity and laser light is about 1.19%.The experimental results show that ArF excimer laser has the highest energy output at temperature of 39? and has a higher energy stability at temperature of 40?48?.