Application of backscattered electron imaging for process development in advanced technology nodes

In this paper, we studied defect discovery and defect review using back-scattered electron (BSE) images. We found that some defects can only be effectively imaged with BSE mode such as hafnium oxide remain at metal gate chemical mechanical polishing (CMP) in the gate last high-k metal gate (HKMG) process. It can also enhance contrast for materials in the bottom of high aspect ratio (HAR) trenches and holes. BSE mode imaging of electron beam review (EBR) is a very useful mode for advanced process technology development and chip production monitoring, especially for middle of line (MOL), which has many buried defects, subsurface defects and thin CMP remains.