Gate current injection in MOSFET's with a split-gate (virtualdrain) structure

Gate current injection into the gate oxide of MOSFETs with a split-gate (virtual drain) structure is examined. The split-gate structure is commonly encountered in flash EEPROM and CCDs. An important parameter characterizing the gate current injection is the ratio φ _b/φ_i (where φ_b is the effective energy barrier for electron injection into gate oxide, and φ_i , is the impact ionization energy). Measurements of φ_b /φ_i at relatively constant vertical and lateral electric fields are reported. Through the use of a novel triple-gate MOSFET, the drain current as well as the lateral and vertical electric field at the point of injection were independently controlled during the measurements. The measured φ_b/φ_i showed a dependence on gate and drain biases not reported previously