An EEPROM cell using a low barrier height tunnel oxide

A new simple method to fabricate a thin oxide with low barrier height is proposed. An oxide is grown on a heavily implanted silicon substrate with As or P in excess of 5 × 10¹⁴/cm². When the oxide was grown in H2O + Ar gas after Ar annealing, the barrier height of the oxide conduction band with respect to the silicon conduction band decreased to 1.8 eV, about one half of the ordinary value of 3.2 eV. This phenomenon was applied to an EEPROM cell, which showed superior WRITE/ERASE characteristics. A moderately implanted As (2.5 × 10¹⁵/ cm²) sample shows excellent WRITE/ERASE endurance, over 10⁶cycles with 2-V Vthwindow, which could not realized by using an ordinary oxide.