Method and apparatus for endpointing while milling an integrated circuit

摘要

A method and an apparatus for endpoint determination when milling an integrated circuit disposed in a substrate. In one embodiment, the substrate is charged to a first polarity while the well regions and active diffusion regions of the integrated circuit are charged to another polarity thus resulting in an electrical bias at the P-N junctions in the substrate. By powering up the integrated circuit in this fashion during milling, endpoint detection can be accurately determined by using a voltage contrast mechanism such as the imaging detector of a focused ion beam (FIB) milling tool. A diffusion boundary can also be determined in accordance with the teachings of the invention by the use of the stage current monitor of the FIB milling tool. The diffusion boundary is determined in accordance with the teachings of the present invention by a change in contrast as detected by the imaging detector of the FIB milling tool or by a change in the stage current as measured by the stage current monitor of the FIB milling tool. By accurately determining when a diffusion boundary is reached, the present invention reduces the risk of inadvertently destroying diffusion regions when exposing features in an integrated circuit during debug.