NUMERICAL STUDY ON THE FLOW-INDUCED-VIBRATION CAUSED BY TWO-PHASE EXTRACTION IN IMMERISON SYSTEM

The immersion system, which maintains a stable liquid environment between the projection lens and the silicon wafer, serves as a critical component in immersion lithography systems for achieving higher-resolution patterning. To maintain the uniformity and stability of the immersion flow field, the immersion lithography must rely on negative pressure extraction and drainage to achieve dynamic sealing of the immersion flow field. However, the gas-liquid two-phase extraction and drainage will cause serious flow-induced vibration problems, which will affect the motion accuracy of the dual worktables and lead to defects such as the stacking and interleaving of exposure lines. Aiming at the sub-millimeter pipelines for two-phase extraction and drainage in the immersion system, a physical model of the gas-liquid "opposing" flow is established. With the help of the open-source software OpenFOAM, numerical analysis is carried out on the flow patterns and flow-induced vibration characteristics inside the pipe. The research results show that the gas-liquid "opposing" flow collides and converges at the bottom of the extraction pipe to form a vortex area, thus inducing pressure fluctuations inside the pipe and two-phase flow-induced vibrations. The characteristics of the two-phase flow-induced vibrations are approximately of the white noise type, which is a superimposition of multiple sinusoidal wave components and broadband white noise. In addition, the gas sealing speed, the wetting characteristics of the wafer surface, and the exposure scanning speed have a relatively large impact on the gas-liquid interface flow patterns and the pressure fluctuation characteristics. Especially when the receding contact angle is around 65°, the two-phase interface is relatively stable and the flow-induced vibration can be effectively suppressed. This study fundamentally reveals the root cause of vibration in the immersion system, providing theoretical support and technical guidance for the optimization of immersion head design and process parameter adjustment. It holds significant engineering value for improving the performance and yield of immersion lithography systems.