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Proceedings Paper

Color filter and numeric aperture selections for image based overlay measurement in critical recording head manufacturing process
Author(s): Gavin Mathias; Yi Liu; Richard Schuster; Aaron Bowser
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Paper Abstract

Overlay control for recording head manufacturing is becoming increasingly challenging as design geometry specifications tighten in the transition to advanced Heated Assisted Magnetic Recording (HAMR) devices. As overlay control requirements for critical patterning layers tighten below 5nm, the need for accurate and robust overlay metrology is key to enabling the patterning roadmap and improving yields. This work focuses on improving Imaged Based Overlay (IBO) metrology to ensure accurate overlay measurements for critical lithography steps in the recording head fabrication process. Selection of the optimal settings for color filter and Numeric Aperture (NA) parameters can have a significant impact on overlay measurement accuracy and Total Measurement Uncertainty (TMU) when setting up a new overlay metrology recipe1-2. These overlay metrology recipe parameters can be selected to minimize the influence of process induced overlay target imperfections on the measured overlay 3. This paper reports our revised workflow for selecting IBO measurement conditions and evaluating pre-existing recipes for robustness. We utilize metrics such as the overlay model residuals, Tool Induced Shift (TIS), and Qmerit error in identifying recipes requiring improvement. The new “Train Log” feature available on KLA’s Archer™ IBO metrology tool platform can be used to compare the through focus contrast precision of different illumination conditions at the time of recipe creation. In this study, we show that an optimization workflow that utilizes the “Train Log” collection of the contrast precision metric and imageless recipes in selecting color filter and numeric aperture settings can significantly improve the overlay measurement repeatability and tool to tool matching.

Paper Details

Date Published: 20 March 2020
PDF: 7 pages
Proc. SPIE 11325, Metrology, Inspection, and Process Control for Microlithography XXXIV, 113252B (20 March 2020); doi: 10.1117/12.2550692
Show Author Affiliations
Gavin Mathias, Seagate Technology (United States)
Yi Liu, Seagate Technology (United States)
Richard Schuster, KLA Corp. (United States)
Aaron Bowser, Seagate Technology (United States)

Published in SPIE Proceedings Vol. 11325:
Metrology, Inspection, and Process Control for Microlithography XXXIV
Ofer Adan; John C. Robinson, Editor(s)

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