Tung & Associates
Tri-tone attenuated phase shift trim mask for double exposure alternating phase shift mask process
Employing a tri-tone attenuated phase shift trim mask in the second exposure of a double exposure alternating phase shift mask (alt-PSM) process is disclosed. A semiconductor wafer is first exposed utilizing a dark field alt-PSM, and then secondly is exposed utilizing a tri-tone attenuated PSM. The tri-tone attenuated PSM may include a transparent substrate, such as quartz, an opaque layer, such as chrome, and an attenuated layer, such as 6% transparency molybdenum silicide (MoSi). The opaque layer has a pattern corresponding to polysilicon gates to be imprinted on the semiconductor wafer, to protect the polysilicon photoresist patterns. The attenuated layer includes assist features to protect forbidden pitch semi-isolated field polysilicon patterns and isolated field polysilicon patterns to be imprinted on the semiconductor wafer.
Taiwan Semiconductor Manufacturing Co., Ltd
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Chung-Hsing
Chang