A self-referenced interferometer for in situ cryogenic wafer curvature measurements

Margaret H Samuels; Alan R Kramer; Christopher J K Richardson

doi:10.1063/5.0189541

A self-referenced interferometer for in situ cryogenic wafer curvature measurements

Rev Sci Instrum. 2024 Apr 1;95(4):045110. doi: 10.1063/5.0189541.

Authors

Margaret H Samuels^{1

2}, Alan R Kramer¹, Christopher J K Richardson^{1

3}

Affiliations

¹ Laboratory for Physical Sciences, 8050 Greenmead Dr, College Park, Maryland 20740, USA.
² Materials Science Program, University of Rochester, 4011Wegmans Hall, P.O. Box 270166, Rochester, New York 14627, USA.
³ Department of Materials Science and Engineering, University of Maryland, 4418 Stadium Dr, College Park, Maryland 20742, USA.

PMID: 38587447
DOI: 10.1063/5.0189541

Abstract

A self-referenced interferometer to measure time-varying curvature in mechanically unstable environments is needed in many applications. One application that demands this measurement technique with fast data acquisition, 2D sensitivity, and insensitivity to vibration is the measurement of thermal strain in thin films in operational environments. The diverging beam interferometer described here demonstrates an angular sensitivity to the local curvature using interferograms captured by a CMOS camera. Two-dimensional Fourier analysis is used to extract curvature changes. The interferometer demonstrates an experimental sensitivity to curvature changes on the order of 10-4 m-1 and is used to measure thermal stresses in a cryogenic environment of a polycrystalline titanium nitride thin film on a silicon wafer that exhibits anisotropic curvature.