For most of the microelectronics industry history, optical lithography has been the backbone for continuing the trend of making features even smaller. The intention of immersion lithography is to increase the index of refraction in the space between the lens and wafer by introducing a high refractive index liquid in place of the low refractive index air that currently fills the gap. Because the liquid acts as a lens component during scan-step process, it must maintain a high and uniform optical quality. Thus, an immersion unit structure must be implemented to keep the flow field from leaking. After analyzing the mechanics of the flow-field in immersion lithography, an immersion unit structure with double gas-curtain sealing and gas-fluid mixing phase collecting was designed and implemented, featuring chemical surface characteristics. Experimental results were analyzed in terms of vacuum degree in collection antrum, input pressure for gas sealing, bubble-trap within flow field, double gas-curtain, double mixing-phase collection, surface characteristics of wafer.
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