CHARACTERIZATION OF POLYSILICON-ENCAPSULATED LOCAL OXIDATION

Device isolation has been most commonly achieved through the use of Local Oxidation of silicon (LOCOS) or LOCOS derivatives. LOCOS is a highly dependable, low-defect isolation technique which explains its continued extensive use. Unfortunately, the inherently large oxide encroachment associated with LOCOS is not compatible with 0.8-mu-m design rules. Many alternative isolation techniques designed to reduce oxide encroachment have been proposed. These alternatives often result in an increase in defectivity and/or process complexity. Polysilicon-Encapsulated Local Oxidation (PELOX) has recently been suggested as an advanced isolation technique that exhibits substantial bird's beak reduction without relying on defective or highly complex processing. PELOX utilizes a polysilicon-filled cavity self-aligned to the nitride edge to achieve oxide encroachment reduction. The physical (scanning electron and transmission electron micrographs) and electrical (electrical channel width, diode leakage, and gate oxide integrity) characterization of PELOX isolation are reported.