Electric discharge laser with acoustic chirp correction
    1.
    发明授权
    Electric discharge laser with acoustic chirp correction 有权
    具有声啁啾校正的放电激光器

    公开(公告)号:US06317447B1

    公开(公告)日:2001-11-13

    申请号:US09490835

    申请日:2000-01-25

    IPC分类号: H01S322

    摘要: Methods and structural changes in gas discharge lasers for minimizing wavelength chirp at high pulse rates. Applicants have identified 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. The timing of the arrival of the pressure wave is determined by the temperature of the laser gas through which the wave is traveling. During burst mode operation, the laser gas temperature in prior art lasers changes by several degrees over periods of a few milliseconds. These changing temperatures change the location of the coincident pressure waves from pulse to pulse within the discharge region causing a variation in the pressure of the laser gas which in turn affects the index of refraction of the discharge region causing the laser beam exiting the rear of the laser to slightly change direction. This change in beam direction causes the grating in the LNP to reflect back to the discharge region light at a slightly different wavelength causing the wavelength chirp. Solution to the problem is to include in the laser chamber structural elements to moderate or disperse the pressure waves and to maintain the laser gas temperature as close as feasible to constant values.

    摘要翻译: 气体放电激光器的方法和结构变化,以最大限度地减少高脉冲波长啁啾。 申请人已经确定了在高脉冲气体放电光刻激光器中的波长啁啾的主要原因,因为从反射回到放电区域的放电的压力波与随后的放电一致。 压力波的到达时间由波浪行进的激光气体的温度决定。 在突发模式操作期间,现有技术的激光器中的激光气体温度在几毫秒的时间内改变了几度。 这些变化的温度改变了放电区域内重合压力波从脉冲到脉冲的位置,导致激光气体的压力变化,这反过来影响放电区域的折射率,导致激光束离开 激光稍微改变方向。 光束方向的这种变化导致LNP中的光栅以稍微不同的波长反射回到放电区域,导致波长啁啾。 解决问题的方法是在激光室结构元件中包括中压或分散压力波,并将激光气体温度保持在尽可能接近的恒定值。