Trap generation in gate oxide layer of MOS structures encapsulated by silicon nitride

Mechanism of trap generation in gate oxide of MOS structure encapsulated by silicon nitride (SiN) is experimentally investigated. Plasma damage results positive charges but few hot-electron traps in the gate oxide layer. Generation of hot-electron traps is attributed to the affects of SiN encapsulant during the device operation. Lower rf power and higher SiH4flow rate for the SiN deposition, and subsequent thermal annealing in H2are desirable to reduce the instability. When fluorinated SiN is used as an encapsulant, the generation of hot-electron traps is successfully suppressed, suggesting possibility to realize higher reliable devices.