Studies on A Sample Preparation Method for HR-SEM and Application in Failure Analysis of Trench TEOS Gauging Measurement in Wafer Fabrication

To identify nitride from oxide layer on the trench, it is necessary to perform BOE chemical staining. However, chemical staining using BOE will damage the oxide layer, causing inaccurate readings in the oxide gauging measurement in the trench. Moreover, damage on the oxide layer caused heavy charging at the side of the trench and the surface of oxide layer. In this paper, we proposed to coat a Cr layer over the trench before chemical staining. The damage problem was eliminated and the measurement of oxide gauging was more accurate. A application case is discussed for trench TEOS gauging measurement.