Study of GIDL Improvement for 2T-SONOS Flash

Abstract

The improvement of Gate induced drain leakage (GIDL) is studied in 2T SONOS (silicon-oxide-nitride-oxide-silicon) nonvolatile memory. High GIDL current from the select gate (SG) introduce inhibit disturb to the neighbor SONOS gate. It is found that these leakage bits impact the overall yield and reliability. In this paper, the variation trend of GIDL leakage with LDD dopant dose, energy and tilt is investigated in detail Results show that GIDL leakage is effectively decreased through increasing tilt and energy or decreasing the dose amount of select gate LDD IMP step. In addition, GIDL leakage also decreased by changing SG LDD dopant step from post poly re-oxidation to post spacer1 etch which increased the space of SG gate to drain. The proposed condition improves GIDL current by one order of magnitude; yield and Vt window are also greatly increased.