REALIZATION OF CAPACITIVE STRUCTURES FROM PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION PROCESS

Multilayer structures metal-insulator-metal are deposited on tungsten wires in view to realize capacitive systems. Both metal and insulator layers are formed in the same reactor by a glow discharge gas phase de composition under a frequency of 35 kHz and a temperature of 375-degre es-C. The materials chosen are tungsten and silicon nitride. Tungsten silicide is deposited as an interphase layer for the lack of adhesion of tungsten to silicon nitride. X-ray diffraction, AES and XPS studies show that tungsten films consists of pure phase alpha with no evidenc e for incorporation of oxygen. Resistivity measurements on tungsten fi lms exhibit a bulk material resistivity of 20 muOMEGA cm. The adhesion layer consists of WSi2 material with a hexagonal crystalline structur e having a resistivity of 560 muOMEGA cm. Silicon nitride is a near st oichiometric material as deduced from AES spectra. Capacitance values versus insulator thickness were measured on cylindrical structures and showed a good fit between results and theory.