Dark-field electron holography for the measurement of strain in nanostructures and devices

Abstract

We present a new method for measuring strain in nanostructures and electronic devices [1]. It is based on a combination of the moiré technique and off-axis electron holography. A hologram is created from the interference between the diffracted beam emanating from an unstrained region of crystal, which serves as the reference, and a beam from the region of interest containing strained crystal. A typical example for these two regions would be the substrate and an active region of a device. The aim is to measure geometric phase differences, from which the deformation can be calculated [2]. Naturally, any other phase contributions should be minimised, notably, dynamic phases due to thickness variations. For this reason, specimens should be prepared with suitably uniform thickness and regions exhibiting bend contours avoided.