Very thin techniques (VTT) for dielectrically isolated MIS devices

MOS multilplex switches have been made in Czochralski silicon down to 2 microns thick. These dielectrically isolated devices exhibit electrical characteristics like those made by conventional techniques. MIS structures of this type can be operated with the substrate acting as a second gate. In this way a device can be biased, without power dissipation, to operate in either depletion or enhancement mode. Tranconductances are, however, reduced, in one mode, by the extra oxide of isolation. These characteristics, as well as applications to radiatior resistant circuits, will be described. The dielectric isolation allows the design of Compatible n- and p-enhancement devices without the disadvantages of multiple diffusion methods. Specifically, there are no large isolation junctions in this structure to create photocurrents in transient radiation environments. Wafers can be prepared with 80 percent of device areas at any nominal thickness, plus or minus one micron. Junction areas of these units are 1200 square microns, a reduction by a factor of 20.