Real-time monitoring of stress evolution during thin film growth by in situ substrate curvature measurement

TL;DR

This paper reviews the use of in situ substrate curvature measurement for real-time monitoring of stress evolution during thin film growth, highlighting its potential and challenges in strain engineering applications.

Contribution

It presents recent applications and new measurements demonstrating the high sensitivity and interpretative complexities of substrate curvature techniques in strain engineering.

Findings

High sensitivity of the substrate curvature method enables detailed stress monitoring.

Correct interpretation of stress data requires complementary characterization.

The technique has significant potential for advancing strain engineering in thin films.

Abstract

Strain engineering is the art of inducing controlled lattice distortions in a material to modify specific physicochemical properties. Strain engineering is applied for basic fundamental studies of physics and chemistry of solids but also for device fabrication through the development of materials with new functionalities. Thin films are one of the most important tools for strain engineering. Thin films can in fact develop large strain due to the crystalline constrains at the interface with the substrate and/or as the result of specific morphological features that can be selected by an appropriate tuning of the deposition parameters. Within this context, the in situ measurement of the substrate curvature is a powerful diagnostic tool allowing a real time monitoring of the stress state of the growing film. This manuscript reviews a few recent applications of this technique and presents new measurements that point out the great potentials of the substrate curvature measurement in strain engineering. Our study also shows how, due to the high sensitivity of the technique, the correct interpretation of the results can be in certain cases not trivial and require complementary characterizations and an accurate knowledge of the physicochemical properties of the materials under investigation.