Polysilicon encapsulated local oxidation

Polysilicon encapsulated local oxidation (PELOX) is proposed as an effective isolation technique that satisfied advanced device requirements without any difficult-to-control structures or processes. Simple modifications to a standard local oxidation of silicon (LOCOS) process flow minimize encroachment without introducing defects. These modifications include an HF dip after nitride patterning to form a cavity self-aligned to the nitride edge, reoxidation of exposed silicon, and polysilicon deposition to fill the cavity. Physical (scanning electron micrographs) and electrical (gate oxide quality, diode integrity, and W/sub eff/) data which indicate that cavity reoxidation is critical to obtaining significant bird's beak reduction without defect introduction are presented. >