Study of dry delineation with Argon sputtering on FIB-milled copper profile

Samples prepared for SEM imaging after Focused Ion Beam (FIB) milling often require staining or delineation on the cross section to distinguish the different layers/features of the device structure. Wet staining using Buffered Oxide Etch (BOE), is one of the most common and economical decoration methods. Since wet etching is difficult to control, artifacts such as copper void and film over-etch may be induced in the samples. Hence, Reactive Ion Etch (RIE) dry staining was considered as the alternative method. In this paper, the RIE dry stain results from several tests with varying RIE staining process parameters revealed unwanted surface contamination on the sample cross section. Further evaluation was performed to study if RIE dry staining with post Argon sputter cleaning is effective to remove the contamination generated on the samples during RIE dry staining.