Using the Scanning Electron Microscope As an Etch Process Monitoring Tool
Original Publication Date: 1988-May-01
Included in the Prior Art Database: 2005-Feb-15
This article describes how a scanning electron microscope (SEM) can be used as an in-line monitoring tool to determine when an integrated circuit contact hole etch process has gone to completion. Extensions of this technique are also featured. With photoresist still on the wafer, a SEM is used to inspect contact holes to determine if etch-through has taken place or if further etching is necessary. The figure shows a typical test site, which may be used as part of a standard chip design, located in the kerf for test purposes or process control. A family of contact areas (targets) are needed to accommodate physical probing and beam probing. Because the SEM uses voltage contrast techniques for viewing targets, an underlying layer of conductive material, which may be electrically activated, is also needed.