Hafnium-doped tantalum oxide high-k gate dielectric films for future CMOS technology

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Title: Hafnium-doped tantalum oxide high-k gate dielectric films for future CMOS technology
Author: Lu, Jiang
Abstract: A novel high -k gate dielectric material , i .e . , hafnium -doped tantalum oxide (Hf -doped TaOx ) , has been studied for the application of the future generation metal -oxidesemiconductor field effect transistor (MOSFET ) . The film's electrical , chemical , and structural properties were investigated experimentally . The incorporation of Hf into TaOx impacted the electrical properties . The doping process improved the effective dielectric constant , reduced the fixed charge density , and increased the dielectric strength . The leakage current density also decreased with the Hf doping concentration . MOS capacitors with sub -2 .0 nm equivalent oxide thickness (EOT ) have been achieved with the lightly Hf -doped TaOx . The low leakage currents and high dielectric constants of the doped films were explained by their compositions and bond structures . The Hf -doped TaOx film is a potential high -k gate dielectric for future MOS transistors . A 5 ? ? ? ? tantalum nitride (TaNx ) interface layer has been inserted between the Hf -doped TaOx films and the Si substrate to engineer the high -k /Si interface layer formation and properties . The electrical characterization result shows that the insertion of a 5 ? ? ? ? TaNx between the doped TaOx films and the Si substrate decreased the film's leakage current density and improved the effective dielectric constant (keffective ) value . The improvement of these dielectric properties can be attributed to the formation of the TaOxNy interfacial layer after high temperature O2 annealing . The main drawback of the TaNx interface layer is the high interface density of states and hysteresis , which needs to be decreased . Advanced metal nitride gate electrodes , e .g . , tantalum nitride , molybdenum nitride , and tungsten nitride , were investigated as the gate electrodes for atomic layer deposition (ALD ) HfO2 high -k dielectric material . Their physical and electrical properties were affected by the post metallization annealing (PMA ) treatment conditions . Work functions of these three gate electrodes are suitable for NMOS applications after 800 ? ? ? ?C PMA . Metal nitrides can be used as the gate electrode materials for the HfO2 high -k film . The novel high -k gate stack structures studied in this study are promising candidates to replace the traditional poly -Si -SiO2 gate stack structure for the future CMOS technology node .
URI: http : / /hdl .handle .net /1969 .1 /4714
Date: 2007-04-25

Citation

Hafnium-doped tantalum oxide high-k gate dielectric films for future CMOS technology. Available electronically from http : / /hdl .handle .net /1969 .1 /4714 .

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