Optimizing ToF-SIMS Depth Profiles of Semiconductor Heterostructures

TL;DR

This paper improves ToF-SIMS depth profiling of semiconductor heterostructures by optimizing sputtering parameters to reduce profile broadening, enabling precise characterization of ultra-thin layers crucial for quantum computing applications.

Contribution

It introduces an optimization method for ToF-SIMS parameters that minimizes profile broadening in semiconductor heterostructures, enhancing measurement accuracy for quantum device fabrication.

Findings

Optimized sputter parameters achieve high-resolution depth profiles.

Accurate measurement of 2 nm thick layers demonstrated.

Guided analysis of heterostructures with quantum wells for qubits.

Abstract

The continuous technological development of electronic devices and the introduction of new materials leads to ever greater demands on the fabrication of semiconductor heterostructures and their characterization. This work focuses on optimizing Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) depth profiles of semiconductor heterostructures aiming at a minimization of measurement-induced profile broadening. As model system, a state-of-the-art Molecular Beam Epitaxy (MBE) grown multilayer homostructure consisting of $^{\textit{nat}}$Si/$^{28}$Si bilayers with only 2 nm in thickness is investigated while varying the most relevant sputter parameters. Atomic concentration-depth profiles are determined and an error function based description model is used to quantify layer thicknesses as well as profile broadening. The optimization process leads to an excellent resolution of the multilayer homostructure. The results of this optimization guide to a ToF-SIMS analysis of another MBE grown heterostructure consisting of a strained and highly purified $^{28}$Si layer sandwiched between two Si$_{0.7}$Ge$_{0.3}$ layers. The sandwiched $^{28}$Si layer represents a quantum well that has proven to be an excellent host for the implementation of electron-spin qubits.