Published online by Cambridge University Press: 25 February 2011
The ability to pattern VLSI wafers by plasma etching through SiO2 without causing structural damage and chemical contamination to the underlying silicon material is today highly desired. Examples are the plasma etching of metal/silicon contact holes and the fabrication of charge injection windows for EEPROM devices. Damage to underlying silicon, which may adversely affect contact resistance, oxide breakdown or charge retention properties, occurs as the oxide is reduced in thickness below a certain penetration depth (Dox). Dox is the effective projected range of damage-producing particles in Si0 2, and is a function of the distributions of energy, mass, etc., of the plasma constituents. In this paper we describe the use of thermal wave modulated reflectance in conjunction with a simple tapered-oxide film structure to measure the depth of penetration of etch-induced damage through SiO 2. Results on the dependence of the penetration depth on RIE self-bias voltage and other observations of etch-induced surface modifications are reported.