Analysing the linearised radially polarised light source for improved precision in strain measurement using micro-Raman spectroscopy

TL;DR

This paper investigates the use of linearised-radially polarised light in micro-Raman spectroscopy to improve the accuracy and precision of strain measurements in semiconductor devices, offering a non-destructive inline testing method.

Contribution

It introduces a novel excitation source for Raman spectroscopy that enhances measurement accuracy compared to traditional linear polarisation methods.

Findings

Radially polarised light significantly improves strain measurement precision.

Numerical simulations confirm increased electric field intensities with this approach.

Experimental results align with TEM benchmarks, demonstrating non-destructive advantages.

Abstract

Strain engineering in semiconductor transistor devices has become vital in the semiconductor industry due to the ever increasing need for performance enhancement at the nanoscale. Raman spectroscopy is a non-invasive measurement technique with high sensitivity to mechanical stress that does not require any special sample preparation procedures in comparison to characterization involving transmission electron microscopy (TEM), making it suitable for inline strain measurement in the semiconductor industry. Indeed at present, strain measurements using Raman spectroscopy are already routinely carried out in semiconductor devices as it is cost effective, fast and non-destructive. In this paper we explore the usage of linearised-radially polarised light as an excitation source, which does provide significantly enhanced accuracy and precision as compared to linearly polarised light for this application. Numerical simulations are done to quantitatively evaluate the electric field intensities that contribute to this enhanced sensitivity. We benchmark the experimental results against TEM diffraction-based techniques like nano-beam diffraction and Bessel diffraction. Differences between both approaches are assigned to strain relaxation due to sample thinning required in TEM setups, demonstrating the benefit of Raman for nondestructive inline testing.