Nitride cladded poly-Si spacer LOCOS (NCPSL) isolation technology for the 1 giga bit DRAM

A novel LOCOS type isolation technology, Nitride Cladded Poly-Si Spacer LOGOS (NCPSL) which is for the 1 giga bit DRAM, has been developed. The features of the NCPSL process are low bird's beak encroachment and long effective isolation length, which are achieved by using substrate silicon recess etching, poly-Si sidewall spacer, and selectively deposited SiN to the poly-Si spacer. NCPSL isolation shows the excellent active definition, high punchthrough voltage, low junction leakage current, hump free transistor characteristic, and good gate oxide integrity. Considering its isolation characteristics, NCPSL is the very practical technology for the isolation of 1 giga bit DRAM.