Stress inspection for overlay characterization

David M. Owen

doi:10.1117/12.2025310

10 April 2013 Stress inspection for overlay characterization

David M. Owen

Proceedings Volume 8681, Metrology, Inspection, and Process Control for Microlithography XXVII; 86812T (2013) https://doi.org/10.1117/12.2025310
Event: SPIE Advanced Lithography, 2013, San Jose, California, United States

Abstract

The understanding and control of stresses accumulated during device fabrication is becoming more critical at advanced technology nodes. Within-wafer stress variations cause local wafer distortions which in turn present challenges for the management of overlay and depth of focus during lithography. This paper describes the use of a comprehensive stress inspection technology, the Coherent Gradient Sensing (CGS) interferometer, for the characterization of stress-induced overlay errors. Using CGS, stresses and wafer distortions induced by any upstream process (or series of processes) can be measured, and the relative contribution of stress-induced overlay associated with individual processes can be evaluated. The CGS technology has two key features that enable the application of stress metrology to lithographic overlay: 1) whole-wafer stress measurement with approximately 800,000 points on a 300mm wafer, 2) patterned wafer stress measurement that is highly insensitive to variations in device structures or materials, such that any location within a die or wafer can be characterized without the need for traditional test structures. Fundamentally, thin-plate theory relates the in-plane stresses in a thin film structure to in-plane strains and displacements. The in-plane displacements in the film due to stress are related to the lithographic overlay. The approach presented here demonstrates the relationship between stress gradients are related to in-plane displacements. Data from case-studies are presented that further shows the correlation between in-plane displacements, measured from wafer distortion and traditional measurement of overlay targets.

Citation Download Citation

David M. Owen "Stress inspection for overlay characterization", Proc. SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII, 86812T (10 April 2013); https://doi.org/10.1117/12.2025310

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