Novel germanium/boron channel-stop implantation for submicron CMOS

A method of improving the electrical field isolation for high density CMOS circuits is proposed using a novel dual germanium and boron channel-stop implant technique, The dual implantation of germanium and boron into the channel-stop regions is shown to increase the field threshold voltage by as much as 40%. This improvement in field threshold voltage is a consequence of reduced boron diffusion and segregation during field oxidation due to the presence of germanium in the field region. There is no degradation to junction and gate oxide breakdown voltage or short-channel MOSFET behavior for these devices. Several techniques are proposed using selective germanium implantation to reduce the process mask count and improve field isolation.