Thickness Control and Targeting in Large Scale Automated XTEM Lamella Preparation

The automation of both, transmission electron microscopy (TEM) imaging and lamella preparation using focused ion beam (FIB) has gathered an enormous momentum in last few years, especially in the semiconductor industry. The process development of current and future microprocessors requires a precise control on the patterning of a multitude of ultrafine layers, several of which are in the order of nanometers. The statistical accuracy and reliability of TEM based metrology and failure analysis of such complex and refined structures across the wafer needs a large-scale sampling, which is feasible only with an automation. An inherent requirement of automating TEM sample preparation entails a need of a robust and repeatable methodology that provides both, a good thickness control and an accurate targeting, on the intended feature in the ultra-thin lamella. In this work, key factors that impact both these aspects of a TEM lamella preparation will be discussed. In addition, steps needed to ensure that FIB toolsets consistently and reliably produce high quality samples, will be highlighted.