基于液滴锡靶LPP-EUVL光源多层膜的溅射损伤研究

基于Navier-Stokes方程的自相似解，研究了最小质量限制液滴Sn靶激光等离子高能离子的时空分布特性，并将该结果应用于高能离子碎屑刻蚀导致的极紫外光刻(EUVL)光源收集镜寿命的评估.对于不同的绝热膨胀指数γ＝1.67、1.3和1.1，数值计算了激光等离子体平均电离度、等离子体羽辉尺寸、羽辉膨胀速率和离子动能随时间的演化，并得到了高能Sn离子碎屑通量的角分布及其轰击溅射Ru、Mo和Si膜的溅射产额及溅射刻蚀速率.研究发现，激光液滴靶等离子体中的高能Sn离子对Mo，Si多层膜的溅射刻蚀率的角分布满足cos3θ的关系.对EUVL光源而言，为了延长EUV收集镜寿命，降低激光等离子体电离度和采用最小质量限制液滴Sn靶是一条有效的途径.

Sputtering damage of multilayer coatings for LPP-EUVL light source based on Sn droplet target

Based on the self-similar solution of Navier-Stokes equations， properties of fast ion debris emitted from laser-produced mass-limited plasma had been theoretically investigated for an application to extreme ultraviolet lithography (EUVL). Using numerical technology， the average ionization degree， the plasma plume size， the expansion velocity and the ion kinetic energy evolutions for three values of adiabatic exponent γ＝1.67， 1.3 and 1.1 were presented. The angular distribution of fast ion debris fluxes and erosion rates due to sputtering yield for Ru， Mo， and Si under tin ion bombardment were calculated. It was found that angle dependence of the erosion rate due to sputtering yields Y of Si and Mo with Sn showed cos3θ profiles. The formation of low ionization degree and minimum-mass plasma for EUV sources are expected to result in a significant increase in the collector mirror lifetime.