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Overlay target and measurement procedure to enable self-correction for wafer-induced tool-induced shift by imaging sensor means
Overlay target and measurement procedure to enable self-correction for wafer-induced tool-induced shift by imaging sensor means
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机译:覆盖目标和测量程序,以通过成像传感器装置对晶片引起的工具引起的偏移进行自我校正
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摘要
Imaging instruments for inspecting products, such as semiconductor chips, are calibrated by providing a reference test structure having features which can be located by optical measurements not subject to tool-induced shift and wafer-induced shift experienced by the imaging instrument, thereby enbabling self correction of the imaging instrument. The reference test structure, which has a plurality of target units formed therein, is first qualified using the optical measurements, and is then used to calibrate the imaging instrument. The optical measurements may be made by a supplementary alternative imaging-sensor means which can be integrated into existing imaging instrument architecture. A series of test structure elements may be fabricated with one component of each being spaced at progressively greater distances from an arbitrary baseline, such that a zero overlay element may be identified by the alternative imaging sensor means.
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