OPTIMIZATION OF POLYSILICON ENCAPSULATED LOCAL OXIDATION OF SILICON -CAVITY DIMENSION EFFECTS ON MECHANICAL-STRESS AND GATE OXIDE INTEGRITY

Based on experimental and simulation results, this paper presents an a nalysis of the relationships between mechanical stress, cavity dimensi ons, and gate oxide integrity in the polysilicon encapsulated local ox idation of silicon (PE-LOCOS) lateral isolation technique. The influen ce of cavity dimensions on bird's-beak formation and mechanical stress at the active area edges is studied by means of Raman spectroscopy an d cross-sectional transmission electron microscopy (TEM), and is model ed with accurate two-dimensional simulations. Three-dimensional effect s at active area corners, which can strongly influence the gate oxide integrity, are evaluated with charge to breakdown measurements, emissi on microscopy, and cross-sectional TEM. An optimized lateral isolation module for 0.25 micron complementary metal oxide semiconductor techno logies is presented, with good bird's-beak dimension control, limited mechanical stress buildup, and excellent gate oxide integrity.