Increased copper outplating from dilute HF solutions on microstructurally modified silicon surfaces

Copper contamination during dilute HF (DHF) cleaning is one of the critical issues in silicon semiconductor device manufacturing. In this paper, copper outplating from DHF solution onto silicon surfaces was studied with transmission electron microscopy. It was found that copper ions preferentially deposited only at the amorphous silicon regions. A sharp circular boundary between the copper deposited and undeposited areas was obtained which was found to correspond to the amorphous-crystalline transition in the substrate. The deposited copper panicles were face centered cubic polycrystalline structure with particle size ranging from 5 to 60 nm. Similar Cu deposition patterns were also found on other samples with scanning electron microscopy. The pattern formation of copper deposition was attributed to the preferential nucleation of copper in the amorphous regions.