A new fully recessed-oxide (FUROX) field isolation technology for scaled VLSI circuit fabrication

A more reliable process for near-zero bird´s beak and fully recessed field isolation structure has been developed, which effectively reduces the narrow channel width effects which exist in the conventional local oxidation of silicon (LOCOS) processing. This proposed new process mainly consists of a new nitride masking structure for a two-step field oxidation and a self-aligned field implantation. Using a thin nitridized oxide as a buffer layer underneath the oxidation mask, the bird´s beak of the first field oxide is largely reduced by the nitridation-enhanced interface sealing ability. No additional masking steps are required. The MOSFET´s with various channel widths have been fabricated and characterized, and comparisons between the new isolation technique and the conventional LOCOS have been made. The improvement in device performance using the proposed isolation technique in MOS/VLSI fabrication is also clearly demonstrated.