Strain determination in the Si channel above a single SiGe island inside a field effect transistor using nanobeam x-ray diffraction

TL;DR

This study uses nanobeam x-ray diffraction to measure the tensile strain in the silicon channel of a field effect transistor with a single SiGe island, revealing strain levels significantly higher than conventional methods.

Contribution

It demonstrates the application of nanobeam x-ray diffraction to directly measure strain in a fully-processed device with high spatial resolution, providing new insights into strain engineering in transistors.

Findings

Maximum in-plane tensile strain of about 1% in the Si channel

Strain levels are 3-4 times higher than in state-of-the-art dislocation-free strained Si

X-ray diffraction combined with finite element simulations effectively characterizes strain fields

Abstract

SiGe islands are used to induce tensile strain in the Si channel of Field Effect Transistors to achieve larger transconductance and higher current driveabilities. We report on x-ray diffraction experiments on a single fully-processed and functional device with a TiN+Al gate stack and source, gate, and drain contacts in place. The strain fields in the Si channel were explored using an x-ray beam focused to 400 nm diameter combined with finite element simulations. A maximum in-plane tensile strain of about 1% in the Si channel was found, which is by a factor of three to four higher than achievable for dislocation-free tensile strained Si in state-of-the-art devices.