Sideways FIB TEM sample preparation for improved construction analysis in TEM

Conventional TEM sample preparation for full-stack BEOL construction analysis (CA) has several issues such as the difficulty of achieving full metal layers intact in a single lamella, and also a curtaining effect that adversely impacts TEM analysis. This paper presents and successfully demonstrates an alternative sample preparation technique for preparing CA samples with full-BEOL metal stack. The procedure involves changing the orientation of the lamella by rotating the sample during in situ FIB attachment and milling it sideways to achieve lamella thickness of 100 nm, with uniform thickness at the area of interest. With this new method, full metal layers can be preserved while minimizing the curtaining effect often observed in heterogeneous TEM sample preparation.