Calculations were carried out to study the effectiveness of a gas curtain for mitigating contamination from hydrocarbon gases in extreme ultraviolet (EUV) lithography tools. The momentum, energy and mass transport in the curtain and surrounding regions were calculated using a two dimensional finite volume model of a lithography tool. Argon was used for the gas curtain. The results from the calculations quantify time relationship between the argon flow rate and the hydrocarbon partial pressure in the region of the optical elements. In general, the hydrocarbon partial pressure decreases as the mass transfer Peclet number, Pe = Vh/D, increases, where V is the velocity of the argon, h is the thickness of the gas curtain and D is the mass diffusivity. An argon flow rate of 12.2 torr.1/s is required to reduce the hydrocarbon partial pressure from 10(-7) to 10(-10) torr in the specific lithography tool considered here. The EUV transmission in the tool with the gas curtain is 0.93. This is a large improvement over the 0.5 transmission that would result by using a solid filter to contain the hydrocarbon gas.
