The effect of convergence angle on strain measurement precision

Gatan instrument used

The GIF Continuum^® with Stela^®*, and the STEMx^® system leverage eaSI™ technology to synchronize the STEM probe with the Stela fast frame rate to acquire high-quality 4D STEM datasets at high speed.

Background

Strain engineering tailors the functional properties of a thin film by intentionally inducing tensile or compressive strain in the film. Measuring the induced strain with high spatial resolution is especially important in state-of-the-art metal-oxide-semiconductor field- effect transistor (MOSFET) since the conduction channels are <20 nm in width. A Kossel-Möllenstedt condition must be used when mapping strain with 4D STEM, where the Bragg-angle (θ_B) is larger than the semi-convergence angle (α). Here, we show that the semi- convergence angle (α) greatly affects the precision of the strain measurement.