Abstract
We demonstrate the results of a strain (stress) evaluation obtained from Raman spectroscopy measurements with the super-resolution method (the so-called super-resolution Raman spectroscopy) for a Si substrate with a patterned SiN film (serving as a strained Si sample). To improve the spatial resolution of Raman spectroscopy, we used the super-resolution method and a high-numerical-aperture immersion lens. Additionally, we estimated the spatial resolution by an edge force model (EFM) calculation. One- and two-dimensional stress distributions in the Si substrate with the patterned SiN film were obtained by super-resolution Raman spectroscopy. The results from both super-resolution Raman spectroscopy and the EFM calculation were compared and were found to correlate well. The best spatial resolution, 70 nm, was achieved by super-resolution Raman measurements with an oil immersion lens. We conclude that super-resolution Raman spectroscopy is a useful method for evaluating stress in miniaturized state-of-the-art transistors, and we believe that the super-resolution method will soon be a requisite technique.
Highlights
Raman spectroscopy is used as a stress evaluation method for strained Si, which is a technique for improving device performance
The spatial resolution of Raman spectroscopy was improved by the use of digital processing technology provided by the super-resolution method, along with a highnumerical-aperture lens
A Si substrate with a patterned SiN film was used as a strained Si sample
Summary
Raman spectroscopy is used as a stress evaluation method for strained Si, which is a technique for improving device performance. The Raman spectroscopy is advantageous because it permits the nondestructive and precise measurement of stress in Si with relatively high spatial resolution. The spatial resolution of Raman spectroscopy was improved by the use of a high-numericalaperture (NA) immersion lens [6, 7]. The spatial resolution of current Raman measurements is insufficient to evaluate state-of-the-art MOSFETs, because the spatial resolution of an optical measurement cannot far exceed its wavelength due to the diffraction limit. The digital processing technology of the super-resolution method permits the evaluation of the spatial resolution beyond the optical diffraction limit
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