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A compact physical CD-SEM simulator for IC photolithography modeling applications

Scanning Electron Microscopy (SEM) is widely used to measure Critical Dimensions (CD) in semiconductor lithography processes. As the size of transistors keeps shrinking, the uncertainty associated with CD-SEM accounts for a fast growing contributor to the entire manufacturing error budget. Capability to predict the metrology results from a CDSEM is highly desirable to quantify the uncertainty of metrology. Simulation has proven to be a valuable means of studying both SEM metrology and photolithography. Monte-Carlo based simulators are generally used to model the detailed image formation process of a CD-SEM, while physics-based photolithography simulations, such as PROLITH™ are commonly used for lithography modeling. However, the high computational cost limits the application of Monte- Carlo based CD-SEM simulations in conjunction with lithography simulation. We present here a compact physical CDSEM simulator which simplifies the image formation process while preserving many essential SEM imaging mechanisms. Several applications of our CD-SEM simulator are presented to demonstrate the predicting capability compared with experiments.