Advanced OSELO isolation with shallow grooves for high-speed submicrometer ULSIs

A submicrometer (0.7-μm) isolation structure using processes that are compatible with the LOCOS processes has been developed. This novel isolation structure, called OSELO II, is fabricated using modified local oxidation technology and an offset structure. The offset structure is characterized by a framed Si₃N₄ mask for bird-beak-free oxidation, formation of shallow self-aligned Si grooves, and two-step boron-ion implantation that decreases current leakage along the isolation sidewall. This isolation technology provides (1) an active MOS transistor having a mask-defined 0.8-μm channel width giving 60% more drain current than the conventional transistor with LOCOS isolation (2) 0.6-μm minimum isolation length, which equals the isolation length between the two adjacent active transistors and is also defined by the mask length, and (3) 20% lower parasitic junction capacitance compared with the LOCOS structure. These results demonstrate that the process is promising for high-speed submicrometer ultralarge-scale integrated devices