Study On The Behavior Of The Gas-liquid Interface Induced By The Wall-jet Impingement

The effective sealing for immersion liquid is the key technology to improve the yield of silicon wafer in immersion lithography. The research background is based on the process of gas sealing for immersion liquid in immersion lithography. According to the gas sealing mechanism for immersion liquid in which the gas-liquid interface is confined by the wall-jet, a foundational experiment of a gas-jet penetrating into a liquid sheet was built, the systematic study on the behavior of gas-liquid interface induced by the wall-jet impingement was carried out. This study was very significant to disclose the behavior of gas-liquid interface in the process of gas sealing, optimize the design of gas sealing process for improving the gas-liquid stability and finally achieve the effective sealing for immersion liquid in immersion lithography.This thesis employed the exploration of experimental phenomena and dimensionless normalized analysis for results as the main research ways, combined with the technology of numerical simulation and the method of digital image processing, to systematically investigate the behavior of gas-liquid interface under the wall-jet impingement induced by a gas-jet penetrating into a liquid sheet. Firstly, the characteristic phenomena were observed in the stable and unstable states of gas-liquid interface under the wall-jet impingement. The influence law to the stability of the gas-liquid interface with the penetrating parameters was explored, the destabilization mechanism of the gas-liquid interface was revealed and the judging criterion for the stability of the gas-liquid interface was given in a dimensionless normalized formulation. Secondly, the phenomenon of stable cavity accompanying with the circular dry spot on the solid substrate surface was observed by static resident behavior of the gas-liquid interface, the parametric law of the dry spot diameter as the cavity characteristic size was analyzed. The static mechanical equilibrium model at the gas-liquid-solid interface was built, the dimensionless normalized expression between the characteristic size of cavity and penetrating parameters was derived through simplifying that model, and the development law of the characteristic size of cavity with the penetrating parameters in a dimensionless normalized formulation was generalized. Finally, the relationship of the behavior of gas-liquid interface extreme swing and surface wave propagation with the strength of wall-jet disturbance was explored, the flow law of dynamic vortex in the surface wave propagation was revealed, and the dimensionless normalized results of the surface wave propagation frequency with the penetrating parameters was given by dimensional analysis. The core contents in this thesis are as follows:1. The characteristic of the gas-liquid interface stabilityAccording to the gas sealing mechanism for immersion liquid in which the gas-liquid interface is confined by the wall-jet, a foundational experiment of a gas-jet penetrating into a liquid sheet was developed. The characteristic phenomena were observed in the stable and unstable states of gas-liquid interface under the wall-jet impingement. The influence law to the stability of the gas-liquid interface with the penetrating parameters was explored. The relationship between the jet height and the strength of wall-jet disturbance was established through the qualitative analysis of the gas-liquid interface extreme profiles and surface wave propagation frequency. By reducing the jet height, the characteristic phenomenon of droplets splatter was obtained from stable state to unstable state when the gas-liquid interface destabilized by the wall-jet. According to the droplets splatter, the mechanism of Rayleigh instability at the gas-liquid interface triggered by the high propagation frequency of surface wave was revealed. The critical jet height was obtained by the characteristic phenomenon of droplets splatter as the instability criterion, and the judging criterion of the gas-liquid interface stability was given in a normalized reciprocal curve by the dimensionless parameter of the Froude number and the critical jet height.2. The static behavior of gas-liquid interfaceThe phenomenon of stable cavity accompanying with the circular dry spot on the solid substrate surface was obtained by the gas-liquid interface static resident behavior. The parametric law of the dry spot diameter as the cavity characteristic size was analyzed. The static mechanical equilibrium model at the gas-liquid-solid interface was built and simplified according to the Young-Dupre law. The dimensionless normalized expression between the characteristic size of cavity and penetrating parameters was derived by the dimensionless Gaussian distribution of pressure induced by a gas-jet impingement on a solid substrate. Based on this dimensionless normalized expression, the normalized linear relationship was obtained between the dimensionless characteristic cavity size (D/h) and a combined dimensionless parameter of the Froude number and the ratio of nozzle diameter to jet height (d/h). In addition, the linear law of the slope of normalized fitting line with the nozzle diameter was further obtained.3. The dynamic behavior of gas-liquid interfaceThe relationship of the behavior of gas-liquid interface extreme swing and surface wave propagation with the strength of wall-jet disturbance was explored. Taking advantage of the numerical simulation technology, the flow law of dynamic vortex in the surface wave propagation was revealed. The parametric law of surface wave propagation frequency was generalized. The decay nature exponential law of the surface wave propagation frequency with a combined dimensionless parameter of the Froude number and the ratio of jet height to nozzle diameter (h/d) was proposed as a dimensionless normalized formulation.