ELECTRICAL AND MATERIAL PROPERTIES OF METAL SILICATE DIELECTRICS AND METAL GATE ELECTRODES FOR ADVANCED CMOS DEVICES

摘要

This paper reports on the electrical and material properties of ultra-thin hafnium silicate films (HfSi_xO_y) and the properties of various metal gate electrodes for advanced CMOS devices. Excellent C-V and I-V characteristics have been obtained with HfSi_xO_y films with an equivalent oxide thickness of 1.2 nm, indicating that this material is an excellent gate dielectric candidate for aggressively scaled CMOS devices. Good stability of HfSi_xO_y with polysilicon gate electrodes was achieved up to 900℃. Aluminum, on the other hand, was found to readily interact with HfSi_xO_y resulting in a tri-layer gate dielectric. Various metal gates were evaluated on SiO_2. TaN was found to provide reasonable gate current and optimal NMOSFET workfunction values. Ta resulted in higher gate leakage and had inferior thermal stability. Other metals such as Hf, Zr and Ti were found to be very inadequate causing a reduction of the dielectric.