Sb+-Implanted Buried Layer Beneath Thick Oxide Applied for Vertical Fet
Diffusion procedure of implanted Sb in Si including post- oxidation to μm-thickness is investigated in order to reduce implantation-induced damage influence and to fabricate n+-buried layer beneath thick oxide. Implanted and diffused profiles of Sb are measured by ion backscattering technique and the defects are studied by Sirtl etching method. Implanted Sb atoms are accumulated at the interface of the advancing oxide front after oxidation,i.e., implanted Sb is carried inward with the oxidation speed. Because of strong segregation property, loss of implanted Sb is minimal even after the oxidation to 1 –2 μm thickness. Accumulated Sb is diffused into the substrate to form n+-layer by the subsequent drive-in diffusion in the N2 atmosphere. The damage effect is- significantly lowered as the oxide thickness becomes larger by one or two orders magnitude than Rp of Sb ions. The n+p diodes subjected to the oxidation exhibit small reverse leakages and hard breakdown. This doping method is applied to fabricating a fine mesh gate of vertical FET. The buried gate region and satisfactory triode characteristics of p-channel FET are realized.
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