DIRECT EVIDENCE OF GATE OXIDE THICKNESS INCREASE IN TUNGSTEN POLYCIDE PROCESSES

Abstract

The increase of the "effective" gate oxide thickness for W-polycide processes is studied. The samples with as-deposited and annealed W polycide are analyzed by secondary ion mass spectrometry, transmission electron microscopy (TEM), and high-frequency CV measurements. The TEM cross section shows that the gate oxide thicknesses are approximately 244 and approximately 285 angstrom for as-deposited and 1000-degrees-C annealed samples, respectively. The TEM results agree with that from CV measurements. The TEM analyses provide a direct physical evidence of an additional oxide thickness (approximately 41 angstrom) during the W-polycide annealing.