Method of calibrating WEE exposure tool
 The invention provides four sub-patterns located at the periphery of the wafer surface at 90-degree intervals. Each of the four sub-patterns is divided into four alignment scales where each alignment scale is yet again subdivided into a multiplicity of alignment marks. This multiplicity of sub-patterns and alignment scales with each scale having a multiplicity of alignment marks results in very accurate and convenient alignment capability. 
Taiwan Semiconductor Manufacturing Company, Ltd.
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Jung-Hau Shih-Chang Wen-Chong Yung-Dar
Hsiue Shih Chiang Chen