A new self-aligned VLSI Isolation process using thin-metal lift-off

A new Self-Aligned Isolation process using thin-metal Lift-off (SAIL) has been developed for NMOS VLSI circuits. In this process, a field oxide is grown first, followed by a channel-stop implant that is self-aligned to the active area. The self-alignment is achieved through a lift-off process that utilizes only thin metal. The self-alignment of channel-stop implant to active area is shown to improve the breakdown voltage of MOSFET devices. Direct window isolation is used to eliminate oxide encroachment and reduce outdiffusion of boron channel-stop implant into the active area. As a result, the narrow width effect is minimal. Since thin-metal lift-off can be performed reproducibly with high yield, this makes SAIL a viable process for VLSI fabrication.