Realizing sensitive, high throughput and robust overlay measurement is a challenge in current 14nm and advanced upcoming nodes with transition to 300mm and upcoming 450mm semiconductor manufacturing, where slight deviation in overlay has significant impact on reliability and yield1). Exponentially increasing number of critical masks in multi-patterning lithoetch, litho-etch (LELE) and subsequent LELELE semiconductor processes require even tighter overlay specification2). Here, we discuss limitations of current image- and diffraction- based overlay measurement techniques to meet these stringent processing requirements due to sensitivity, throughput and low contrast3). We demonstrate a new electrical measurement based technique where resistance is measured for a macro with intentional misalignment between two layers. Overlay is quantified by a parabolic fitting model to resistance where minima and inflection points are extracted to characterize overlay control and process window, respectively. Analyses using transmission electron microscopy show good correlation between actual overlay performance and overlay obtained from fitting. Additionally, excellent correlation of overlay from electrical measurements to existing image- and diffraction- based techniques is found. We also discuss challenges of integrating electrical measurement based approach in semiconductor manufacturing from Back End of Line (BEOL) perspective. Our findings open up a new pathway for accessing simultaneous overlay as well as process window and margins from a robust, high throughput and electrical measurement approach.
Devender Devender, Xumin Shen, Mark Duggan, Sunil Singh, Jonathan Rullan, Jae Choo, Sohan Mehta, Teck Jung Tang, Sean Reidy, Jonathan Holt, Hyung Woo Kim, Robert Fox, and D. K. Sohn, "High-throughput electrical characterization for robust overlay lithography control," Proc. SPIE 10145, Metrology, Inspection, and Process Control for Microlithography XXXI, 101450K (Presented at SPIE Advanced Lithography: February 28, 2017; Published: 28 March 2017); https://doi.org/10.1117/12.2260707.
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