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

In this paper, gate current injection into the gate oxide of MOSFET's with a split-gate (virtual drain) structure is examined. The split-gate structure is commonly encountered in flash EEPROM and CCD's. An important parameter characterizing the gate current injection is the ratio φb/φi (where φb is the effective energy barrier for electron injection into gate oxide, and φi is the impact ionization energy). We present new experimental data of the ratio φb/φi measured at relatively constant vertical and lateral electric fields. Through the use of a novel triple-gate MOSFET, the drain current as well as the lateral and vertical electric fields at the point of injection were independently controlled during the measurements. The measured φb/φi showed a dependence on gate and drain biases not reported previously.