超精密外差利特罗式光栅干涉仪位移测量系统

A displacement measurement system for ultra-precision heterodyne Littrow grating interferometer

开展了扫描干涉光刻机工作台超精密位移测量的实验研究,以提高扫描干涉光刻机的环境鲁棒性。针对扫描干涉光刻机工作台位移测量精度,提出了新型高环境鲁棒性外差利特罗式光栅干涉仪测量系统。介绍了系统测量原理,设计了测量系统,提出了基于Elden公式的系统死程误差建模方法。设计制造了尺寸仅为48mm×48mm×18mm的光栅干涉仪。基于误差模型计算了死程误差,计算结果表明:对于1.52mm死程的光栅干涉仪,宽松的环境波动指标(温度波动为0.01℃、压力梯度为±7.5Pa、相对湿度波动为1.5%、CO2含量波动为±50×10-6)仅引起±0.05nm的死程误差。最后,设计了基于商用双频激光平面镜干涉仪的测量比对系统,开展了光栅干涉仪原理验证实验和测并量稳定性实验。原理验证实验表明:光栅干涉仪原理正确且系统分辨率达0.41nm。测量稳定性实验表明:常规实验室环境下,环境波动引起的死程误差为7.59nm(3σ)@<0.9Hz&1~10Hz,优于同等环境条件下平面镜干涉仪的31.11nm(3σ)@<0.9Hz&1~10Hz。实验结果显示系统具有很高的环境鲁棒性。

The ultra-precision displacement measurement was researched for the work table of a Scanning Beam Interference Lithography（SBIL）tool to improve its environmental robustness.For the displacement measuring requirement of the work table of the SBIL tool,a novel heterodyne Littrow Grating Interferometer（GI）displacement measurement system with high environmental robustness was proposed.The measuring principle of the heterodyne Littrow grating interferometer was introduced,and the design of the system and dead path error modeling method based on Elden equation was performed.An integrated mini grating interferometer with a size of 48 mm×48 mm×18 mm wasfabricated.Then,the dead path error of the system was calculated based on the model.The calculation result indicates that the dead path error caused by a relative large environmental fluctuation（temperature fluctuation in 0.01 ℃,pressure fluctuation in ±7.5 Pa,humidity fluctuation in 1.5%,and CO2 content fluctuation in ±50×10-6）is only ±0.05 nm.Finally,a comparison system based on the commercial plane mirror interferometer（PMI）and GI was designed for the principle verification and measurement stability experiment.The principle verification demonstrates that the principle of the system is right and the resolution reaches to 0.41 nm.The measurement stability experiment shows that the dead path error of GI and PMI caused by the environmental fluctuation are respectively 7.59 nm（3σ）@〈0.9 Hz＆1~10 Hz and 31.11 nm（3σ）@〈0.9 Hz＆1~10 Hz in a conventional laboratory environment,which indicates the environmental robustness of the GI is higher than that of the PMI.