This paper discusses the optimization of process conditions on a 193 nm immersion lithography cluster tool to minimize
defects. A 45 nm gate process was selected for optimization but a 65nm reticle was used for defect testing so that a nonimmersion
baseline could be collected for comparison. Previous testing has shown defect counts and density are
sensitive to rinsing of wafers before and after exposure. This sensitivity was dependent on the topcoat contact angle
and resist-plus-topcoat porosity. This paper expands on that study in several ways. (1) The immersion process was
simulated by scanning a develop rinse nozzle to observe, with a microscope, any peeling that could cause contamination
in the exposure tool. (2) Different EBR strategies were compared to reduce defects causing by edge residue while
maximizing the productive area of the wafer. (3) The appearance of some defect types was found to be related to the
delay between exposure and post rinse. (4) Bake time and temperature were also added to the testing to determine if the
impact to the film composition would influence the number of defects. (5) The addition of HMDS before BARC was
tested as a way to control defects caused by delaminating at the edge of the wafer. The paper distinguishes between
defects which are specific to the immersion process and those that would still be expected to occur in dry processing.
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