THICKNESS DETERMINATION OF THIN INSULATING LAYERS

Thin insulating films (Si3N4 on titanium-substrate) with various thick nesses (40-360nm) are investigated with EPMA (electron probe micro ana lysis): A carbon- and, alternatively, gold-coating is applied to avoid charging phenomena and beam deflection. The alteration of the shape o f the depth distribution function due to the insulating property is co nsidered by applying an electrostatic model (proposed by Cazaux) of a charged dielectric cylinder. A Monte-Carlo simulation is performed sim ulating the charging of the specimen by assuming a precharge and modif ication of the mean free path in the insulator. Experimentally derived k-ratios for Si3N4-films are verified quantitatively. The applicabili ty of the results to other insulating materials - especially with rega rd to different preparation-techniques - is discussed.