Experimental Study on the Photoelastic Coefficient and Its Wavelength Dispersion for Quantitative Imaging of Residual Strain in Commercial SiC Substrates

• Published in: Journal of electronic materials 2023-08, Vol.52 (8), p.5172-5177
• Main Authors: Fukuzawa, Masayuki, Kudo, Nobuya
• Format: Article
• Language: English
• Subjects: 19th Conference on Defects-Recognition; Birefringence; Characterization and Evaluation of Materials; Chemistry and Materials Science; Electronics and Microelectronics; Imaging; Imaging and Physics in Semiconductors (DRIP XIX); Instrumentation; Materials Science; Optical and Electronic Materials; Polariscopes; Regression analysis; Signal to noise ratio; Silicon carbide; Silicon substrates; Solid State Physics; Topical Collection: 19th Conference on Defects (DRIP XIX); Wavelengths
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-023-10473-z

The absolute difference between two photoelastic coefficients p 11 - p 12 and its wavelength dispersion have been experimentally studied in commercially available (0001) 4H silicon carbide substrates by using originally developed imaging polariscopes (xIPs) with different light-source wavelengths ( λ  = 630 nm, 940 nm, and 1200 nm). The simple three-point bending test was adopted to measure the distribution of birefringence Δ n in a small beam under an external load. Additionally, numerical simulation was performed to accurately estimate the distribution of σ 1 - σ 2 in the beam, even with its size restriction. The value of p 11 - p 12 was evaluated by regression analysis on the value pairs of σ 1 - σ 2 and Δ n examined under various external loads. In order to avoid the effect of residual strain in the sample, the regression analysis was performed at many positions over the sample rather than a few representative points as is adopted conventionally. The value of p 11 - p 12 was obtained as 0.040, 0.090 and 0.13 at wavelengths of 630 nm, 940 nm, and 1200 nm, respectively. The wavelength dispersion revealed inverse correlation with photon energy and suggested that p 11 - p 12 may become close to zero at a certain wavelength shorter than 630 nm, implying a technical trade-off between the sensitivity of the photoelastic effect and the signal-to-noise ratio in polariscopic photometry, which is useful for considering the optimal wavelength in quantitative strain imaging with photoelastic technique.