Influence of CoSi Oxidation and Passivation During Silicide Selective Etching on Junction Leakage: Applications to Schottky Diodes Devices

Abstract

For new analogic microelectronic circuits development based on non-linear devices such as Schottky diodes formed in Si active regions, new Co-silicide integrations are required to reduce junction leakages. To gather targeted device requirements, precise Co silicide/Si interface optimization and a limited silicide formation at the active edges is needed. The selective etching during the “Salicide” process plays a real role in the oxidation and/or passivation of the silicide layer. Here, we propose a systematic study including a very large spectrum of experiments around the main parameters of CoSi selective etching. The main conclusions are (1) diode leakages are directly linked to SiO2 layer thickness formed during the SC1 dispense or by air exposure over the CoSi layer, (2) significant effect of dispense flow on SiO2 formation is measured through X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry characterizations; (3) optimized diode leakages together with contact resistances are then demonstrated for low SC1 delivery flow and long dispense time; and (4) major changes in final CoSi2 layer morphology and silicide/silicon interface are observed by transmission electron microscopy-energy-dispersive X-ray analyses for different selective etching processes, which are potentially explained by enrichment in Co atoms at CoSi/Si during SiO2 overlayer growth.