Extreme ultraviolet pellicle cooling by hydrogen gas flow (Conference Presentation)

The advent of extreme ultraviolet (EUV) technology enables much smaller patterns. In order to commercialize EUV technology, some mechanical problems should be studied. Especially, pellicle temperature rising due to EUV exposure is one of the critical problems. It affects on pellicle life expectancy. We can use gas flow to cool down EUV pellicle as well as to blow off the defects fallen between the pellicle and mask. The cooling behaviors of various EUV pellicle types are studied by finite element method. Figure 1 shows the cooling of 50 nm thick p-silicon monolayer pellicle and the cooling rate is increased with the hydrogen gas flow rate, while the cooling rate without H2 flow is very slow so that it might not reach to the room temperature. The same analysis is applied to other known multi-layer pellicles (Fig. 2). Well known ASML and Samsung pellicles are compared to a single p-silicon layer pellicle. As expected, the maximum temperatures of multi-layer pellicles are lower than single-layer pellicle and we can see that the cooling by gas flow for multi-layer is better than that for a single layer. This study might suggest that EUV pellicle cooling is efficient enough to use a single layer pellicle and we might not need to use the multi-layer pellicle which was originally adapted to cool down and extend the lifetime of the pellicle. The deformation and the stress dependency of the various pellicles on the gas flow rate and pressure difference will be also shown.