Evaluation of thick silicon dioxides grown on trench MOS gate structures

Abstract

We have investigated trench MOS gate power devices that utilize trench gate oxide over 20 nm in thickness. Our results show, for the first time, that the leakage characteristics of trench MOS capacitors have a particular local maximum in the leakage current. We call leakage characteristics of a trench MOS capacitor "camel's hump" leakage current. Moreover, the dielectric breakdown of the silicon dioxide (SiO/sub 2/) film in the trench occurs after a specific point. Experiments conducted affirm that the keen convex corner at the trench top edge is the main factor for determining the electrical property of a thick trench MOS gate oxide, and this fact is supported by numerical device simulation. The leakage current can be suppressed by utilizing chemical dry etching (CDE), followed by sacrificial high-temperature oxidation prior to gate oxidation. These factors are considered vital for the development of trench MOS gate power devices.