A high-speed buried channel MOSFET isolated by an implanted silicon dioxide layer

This paper describes a high-speed buried channel MOSFET dielectrically isolated from the substrate through the use of oxygen implantation technology. An implanted silicon dioxide layer is formed just beneath the surface. An n-type epitaxial layer is grown on the remaining thin single-crystal layer at the surface. Then, buried channel MOSFET´s are formed on the n-type layer. The interface between the implanted SiO2and the upper silicon is abrupt, and the interface charge density is 6.9 × 10¹⁰cm^-2. The effective carrier mobility calculated from the drain conductance is 750 cm²/V . s. Leakage current which should be inherent in this device structure can not be observed. Submicron MOSFET´s show much smaller threshold voltage shifts than conventional ones, and this agrees with the results of two-dimensional numerical calculation. A ring oscillator composed of MOSFET´s with 1-µm channel length shows a minimum delay time of 95 ps and a power delay product of 310 fJ at VDDof 15 V.