Studies On Linewidth Narrowing Module And Ring Cavity For Excimer Laser

By the means of immersion lithography and double patterning,193nm ArF excimerlaser source is still the mainstream source of lithography tools. The linewidth of the excimerlasers must be reduced and the pulse energy must be amplified to meet the strictrequirements of lithography. Among the existing technologies, prism-grating combinationand ring cavity are the common linewidth-narrowing module and regenerative amplifierrespectively.First of all, theoretical analysis was carried on the three-prism grating system. Thelinewidth formula of the system was derived based on the dispersion equations of prisms andgrating. Using ZEMAX software, the model for the three-prism grating combination wasbuilt in mixed sequential/non-sequential mode. Thermal stability, rotational sensitivity andtransmission of the prisms were analyzed; it was found that the three-prism grating structurewas better in comparison with two-prism grating structure.Theoretical and experimental studies of ring cavity of TEA CO2laser were also made inthis thesis. The factors which influenced the output energy, such as astigmatism, reflectivityof the coupling mirror, the shape of the coupling mirror were studied, the experimentalresults showed that changes of reflectivity was the major factor that affect the output energy.This work was helpful in the design of ring cavity for excimer laser.At last, experimental study of ring cavity of excimer laser were made. The rectangularring cavity was finally adopted to make experiment, it was found that there were nooscillations in the free oscillating ring cavity; and laser oscillation was only observed with anextra mirror in the direction of the discharge cavity axis, in which multiple peaks were foundin the temporal waveform of pulsed laser radiation, and the interval between the peaks wereequal to the time it takes for light to make one pass across the cavity. These characteristicscould be attributed to the long cavity length. The results of this study provided experimentpreparation for the following researches of injection locking of excimer laser.