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High-Resolution, High-Accuracy, Mid-IR (450 cm-1 less than or equal to} ω less than or equal to} 4000 cm-1) Refractive Index Measurements in Silicon



Deane Chandler-Horowitz, Paul M. Amirtharaj, John R. Stoup


The real and imaginary part of the refractive index of silicon, n(ω) and k(ω), have been measured by using Fourier Transform Infrared (FTIR) transmission spectral data from a double-sided-polished IC grade Si wafer. An accurate independent mechanical measurement of the wafer thickness, t, was required, and two FTIR spectra were used: a high resolution (Δ}ω = 0.5 cm-1) yielding typical channel spectrum dependent mainly on t and n(ω) and a low resolution (Δ}ω = 4.0 cm-1) yielding an absorption spectrum dependent mainly on t and k(ω). Independent analysis of each spectrum gave initial n(ω) and k(ω) estimates which were then used together as starting point values for an iterative fit of the high- and low-resolution spectra successively. The accuracy of n(ω) and k(ω) values determined using this procedure is dependent upon the measurement error in the sample thickness, the absolute transmission values obtained from a sample-in and sample-out method, and the modeling of the influence of wafer thickness nonuniformity and the degree of incident light-beam collimation.
Proceedings Title
Proc., 1998 International Conference on Characterization and Metrology for ULSI Technology
Conference Dates
March 23-27, 1998
Conference Location
Gaithersburg, MD, USA


double-sided polished, FTIR, interference fringes, silicon refractive index, wafer thickness


Chandler-Horowitz, D. , Amirtharaj, P. and Stoup, J. (1998), High-Resolution, High-Accuracy, Mid-IR (450 cm<sup>-1</sup> {less than or equal to} &#969; {less than or equal to} 4000 cm<sup>-1</sup>) Refractive Index Measurements in Silicon, Proc., 1998 International Conference on Characterization and Metrology for ULSI Technology, Gaithersburg, MD, USA (Accessed July 17, 2024)


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Created February 28, 1998, Updated October 12, 2021