Strain measurement in semiconductor FinFET devices using a novel moir\'e demodulation technique

TL;DR

This paper introduces a new moiré demodulation technique with optimized scanning and phase stepping for high-resolution, fast strain measurement in semiconductor FinFET devices, surpassing traditional methods in resolution and simplicity.

Contribution

The paper presents a novel moiré demodulation method with optimized scanning and phase stepping, enabling improved spatial resolution and speed in strain measurement of semiconductor devices.

Findings

Enhanced spatial resolution over conventional moiré imaging.

Comparable accuracy to Nano-beam and Bessel beam diffraction techniques.

No need for specialized diffraction cameras.

Abstract

Moir\'e fringes are used throughout a wide variety of applications in physics and engineering to bring out small variations in an underlying lattice by comparing with another reference lattice. This method was recently demonstrated in Scanning Transmission Electron Microscopy imaging to provide local strain measurement in crystals by comparing the crystal lattice with the scanning raster that then serves as the reference. The images obtained in this way contain a beating fringe pattern with a local period that represents the deviation of the lattice from the reference. In order to obtain the actual strain value, a region containing a full period of the fringe is required, which results in a compromise between strain sensitivity and spatial resolution. In this paper we propose an advanced setup making use of an optimised scanning pattern and a novel phase stepping demodulation scheme. We demonstrate the novel method on a series of 16 nm Si-Ge semiconductor FinFET devices in which strain plays a crucial role in modulating the charge carrier mobility. The obtained results are compared with both Nano-beam diffraction and the recently proposed Bessel beam diffraction technique. The setup provides a much improved spatial resolution over conventional moir\'e imaging in STEM while at the same time being fast and requiring no specialised diffraction camera as opposed to the diffraction techniques we compare to.