Role of base layer in CVD Si/sub 3/N/sub 4/ stack gate dielectrics on the process controllability and reliability in direct tunneling regime

The roles of the base layer in Si/sub 3/N/sub 4//SiON stack gate dielectrics on the dielectric reliability, MOSFET performance and process controllability are investigated. The critical SiON-base layer thickness is determined as /spl sim/1 nm from the TDDB results and the physical analysis based on X-ray photoelectron spectroscopy. The obtained thickness is considered to attribute to the nitrogen profile in the SiON base and the strained layer thickness near SiON/Si interface.