Phase defect detection with spatial heterodyne interferometry

Philip R. Bingham; Kenneth W. Tobin; Marylyn H. Bennett; Pat Marmillion

doi:10.1117/12.536765

24 May 2004 Phase defect detection with spatial heterodyne interferometry

Philip R. Bingham, Kenneth W. Tobin, Marylyn H. Bennett, Pat Marmillion

Proceedings Volume 5375, Metrology, Inspection, and Process Control for Microlithography XVIII; (2004) https://doi.org/10.1117/12.536765
Event: Microlithography 2004, 2004, Santa Clara, California, United States

Abstract

Phase shift techniques introduced in photolithography to further improve resolution produce a new set of challenges for inspection. Unlike the high contrast provided by patterned and unpatterned areas on a binary mask, phase errors do not provide significant contrast changes, since the phase change is imparted by a difference in material thickness. Surface topology measurements can be used to identify phase defects, but methods for surface topology inspection are typically slow or can damage the surface to be measured. In this study, Spatial Heterodyne Interferometry (SHI) has been considered as a possible method for high-speed non-contact phase defect detection. SHI is an imaging technique developed at Oak Ridge National Laboratory that acquires both phase and amplitude information from an optical wavefront with a single high-speed image capture. Using a reflective SHI system, testing has been performed with a mask containing programmed phase defects of various sizes and depths. In this paper, we present an overview of the SHI measurement technique, discuss issues such as phase wrapping associated with using SHI for phase defect detection on photolithographic masks, and present phase defect detection results from die-to-die comparisons on a 248 nm alternating aperture phase shift mask with intentional phase defects.

Citation Download Citation

Philip R. Bingham, Kenneth W. Tobin, Marylyn H. Bennett, and Pat Marmillion "Phase defect detection with spatial heterodyne interferometry", Proc. SPIE 5375, Metrology, Inspection, and Process Control for Microlithography XVIII, (24 May 2004); https://doi.org/10.1117/12.536765

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