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在以准分子激光为光源的步进扫描投影光刻机中,为了精确控制曝光剂量,需要用能量探测器实时、精确地监测单个激光脉冲的能量。研制了一种主要由聚光镜、积分棒、特殊晶体、滤光片、光电探测器和信号处理电路组成的准分子激光脉冲能量探测器;提出采用二阶有源低通滤波电路对窄脉冲信号进行整形处理以降低后续信号处理的难度;搭建测试装置对所研制的能量探测器进行了性能测试。测试结果表明,能量探测器输出的脉冲信号时间参数的实测值与设计值的相对误差约为3%,且其响应时间满足4 k Hz高重频的应用要求;采用双光束比对法消除准分子激光单个脉冲能量波动对测试结果的影响,得到能量探测器的测量重复性为0.26%,在入射光束脉冲能量为0.1~1μJ的动态范围内具有良好线性,其线性拟合方程为V=0.59841E-0.01508,相应的线性相关系数R2=99.976%。测试结果证明二阶有源低通滤波电路可以实现窄脉冲信号整形;设计的能量探测器具有良好的重复性和线性,可用于光刻机中高重频准分子激光单个脉冲能量的精确测量。
In a step-and-scan projection lithography machine using an excimer laser as a light source, in order to accurately control the exposure dose, an energy detector needs to be used to monitor the energy of a single laser pulse in real time and accurately. An excimer laser pulse energy detector mainly composed of condenser, rod, special crystal, filter, photodetector and signal processing circuit was developed. The second-order active low-pass filter circuit was proposed for narrow pulse signal Plastic processing to reduce the difficulty of subsequent signal processing; build a test device for the performance of the developed energy detector test. The test results show that the relative error between the measured value and the designed value of the pulse signal output by the energy detector is about 3%, and the response time meets the application requirement of 4 k Hz high repetition rate. The double beam alignment method eliminates the standard error The influence of single laser pulse energy fluctuation on the test results shows that the energy detector has a good repeatability of 0.26% and a good linearity in the dynamic range of 0.1 ~ 1μJ with pulse energy of incident beam. The linear fitting equation is V = 0.59841 E-0.01508, the corresponding linear correlation coefficient R2 = 99.976%. The test results show that the second-order active low-pass filter circuit can achieve narrow pulse shaping. The designed energy detector has good repeatability and linearity, which can be used to accurately measure the single pulse energy of high-repetition frequency excimer laser in the lithography machine.