Wafer plane inspection with soft resist thresholding

Carl Hess; Rui-fang Shi; Mark Wihl; Yalin Xiong; Song Pang

doi:10.1117/12.801866

17 October 2008 Wafer plane inspection with soft resist thresholding

Carl Hess, Rui-fang Shi, Mark Wihl, Yalin Xiong, Song Pang

Proceedings Volume 7122, Photomask Technology 2008; 71221C (2008) https://doi.org/10.1117/12.801866
Event: SPIE Photomask Technology, 2008, Monterey, California, United States

Abstract

Wafer Plane Inspection (WPI) is an inspection mode on the KLA-Tencor TeraSca^TM platform that uses the high signalto- noise ratio images from the high numerical aperture microscope, and then models the entire lithographic process to enable defect detection on the wafer plane[1]. This technology meets the needs of some advanced mask manufacturers to identify the lithographically-significant defects while ignoring the other non-lithographically-significant defects. WPI accomplishes this goal by performing defect detection based on a modeled image of how the mask features would actually print in the photoresist. There are several advantages to this approach: (1) the high fidelity of the images provide a sensitivity advantage over competing approaches; (2) the ability to perform defect detection on the wafer plane allows one to only see those defects that have a printing impact on the wafer; (3) the use of modeling on the lithographic portion of the flow enables unprecedented flexibility to support arbitrary illumination profiles, process-window inspection in unit time, and combination modes to find both printing and non-printing defects. WPI is proving to be a valuable addition to the KLA-Tencor detection algorithm suite. The modeling portion of WPI uses a single resist threshold as the final step in the processing. This has been shown to be adequate on several advanced customer layers, but is not ideal for all layers. Actual resist chemistry has complicated processes including acid and base-diffusion and quench that are not consistently well-modeled with a single resist threshold. We have considered the use of an advanced resist model for WPI, but rejected it because the burdensome requirements for the calibration of the model were not practical for reticle inspection. This paper describes an alternative approach that allows for a "soft" resist threshold to be applied that provides a more robust solution for the most challenging processes. This approach is just finishing beta testing with a customer developing advanced node designs.

Citation Download Citation

Carl Hess, Rui-fang Shi, Mark Wihl, Yalin Xiong, and Song Pang "Wafer plane inspection with soft resist thresholding", Proc. SPIE 7122, Photomask Technology 2008, 71221C (17 October 2008); https://doi.org/10.1117/12.801866

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