Evaluation of non-destructive etch depth measurement for through silicon vias

Through-Silicon-Via depth inline monitoring is one of the key requirements for implementing TSV technology into high volume production. The Tamar tool using IR from the backside of wafer is demonstrated to have the capability to provide non-destructive inline monitoring of trench depth after plasma etch, even when the backside wafer surface is rough. However, the etch profile is found to be critical to the effectiveness of this tool. A flat TSV bottom with a minimum of at least 1um in width is required for accurate and repeatable measurements.