基于光梳技术的真空度和气体分压测量方法研究

Lithography is the bottleneck for semiconductor manufacturing, and extreme ultraviolet lithography (EUVL) is the most promising choice for manufacturing chips with critical dimensions under 7 nm. To break the foreign monopolization on the high-end lithography, it is urgent for independent research and development of EUVL. The optical environment in the EUVL is vacuumed, and the vacuum degree and partial pressure of pollutant gases must be monitored in real-time. In recent years, as the international metrological system change, the vacuum measurement based optical methods becomes the research hotspot in international vacuum metrology field. There are two main optical methods: refractive index measurement and absorption spectrum measurement. The first method is measuring the gas refractive index with tunable continuous-wave laser and F-P cavity, and only vacuum degree can be obtained. Gas concentration can be deduced from absorption spectrum, and the vacuum degree is calculated. But the absorption of cleaning gas is too weak to be detected. This project is performed aiming at the on-line real-time measurement of the vacuum degree and partial pressure in the EUVL. The vacuum degree is measured by locking the repetition rate of measurement comb and F-P cavity, and the partial pressure is measured by cavity enhanced dual comb spectroscopy. The on-line real-time measurement of the vacuum degree and partial pressure is achieved. This project can provide new metrology and comparison method for monitoring the EUV lithography vacuum system.

光刻机是半导体制造的核心设备，其中极紫外光刻机（EUVL）是目前生产7nm以下工艺器件最有前景的方案。为了打破欧美国家的技术垄断，研发国产EUVL已经迫在眉睫。EUVL内的光学微环境必须维持在真空状态，需要实时监测真空度和污染气体分压。近年来，随着国际计量体系发生变化，基于光学手段的真空计量方法成为国际真空计量领域的研究热点。目前基于光学手段的真空测量方法主要有两种：折射率测量和吸收光谱测量。通过测量折射率只能得到真空度，无法获得气体分压；清洁气体吸收谱线强度极弱，无法通过测量吸收光谱得到真空度。本项目瞄准EUVL真空系统内真空度和气体分压的快速在线测量需求，研究基于光梳技术的真空环境测量原理与方法，利用腔增强双光梳光谱仪中测量光梳重频和增强腔的锁定关系测量折射率，结合污染气体吸收光谱可以实现真空度和气体分压的快速在线测量。该项研究工作可为EUVL真空环境监测提供新的计量和比对手段。

本项目开展了多种光学精密测量方法研究，包括光频梳真空度测量方法、光频梳测距方法和微纳结构几何尺寸测量方法。真空环境实时监测对保障光刻机、国家点火装置等正常运转是必不可少的。开展了基于光频梳的真空测量方法理论研究。高精度大范围绝对测距技术是实现卫星编队飞行和大型零部件装配的重要技术手段。开展了高性能飞秒光频梳光源和光频梳高精度测距技术研究，在100米测量内实现0.08mm测量精度。通过该研究工作，有望为推动我国大型装备制造、航天技术的高速发展提供技术支撑。高深宽比沟槽微结构广泛应用于微机电系统与三维集成电路等领域，是微纳器件的基础性工艺结构。随着器件深宽比的不断提升，对检测设备提出了更高的要求，是急需解决的技术难题。开展了基于深度学习的过焦扫描显微成像测量方法研究，实现了高深宽比微沟槽深度、线宽及侧壁角的高精度测量，最大测量深度大于400微米，最大深宽比达到80:1。通过该研究工作，可以为我国MEMS、3D集成电路提供新的量测手段，为优化制造工艺，提高产品良率提供关键技术支持。