Material and electrical properties of HfxRuy and HfxRuyNz metals as gate electrodes for p-metal oxide semiconductor field effect transistor devices

Abstract

Material and electrical characterizations of sputter-deposited HfxRuy and HfxRuyNz gate electrodes atop atomic layer deposited HfO2 were performed with a focus on optimizing their compositions for suitable applications in p-metal oxide semiconductor field effect transistors (pMOSFETs), since Fermi level pinning is a more severe issue for higher work function metals. The alloys of HfxRuy with effective work functions (EWFs) ranging from 4.4 to 5.0 eV were achieved when the Ru metal ratio was varied from 53% to 74%. Nitrided hafnium ruthenium alloys, HfxRuyNz (0%–25% N), with EWFs of 4.9–5.2 eV were also synthesized. Among these materials, Hf0.26Ru0.74 and Hf0.05Ru0.77N0.18 were determined to have EWFs adequate for pMOSFET devices of 5.0 and 5.2 eV, respectively. The slightly higher than expected EWFs of these metal gates are attributed to the presence of oxygen. The depth profiling of the as-deposited gate stacks showed reasonably sharp interfaces between the gate electrode and the gate dielectric with the HfxRuy alloy exhibiting better interfacial properties. Upon annealing, the HfxRuy alloys were found to be more stable than the HfxRuyNz alloys on HfO2.

Integrations and challenges of novel high-k gate stacks in advanced CMOS technology

“…Several binary A x B 1Àx alloys made from low U m and high U m metals have been investigated by using co-sputtering or ''interdiffusion'' process, such as Hf x Ru 1Àx [273], Ta-Ru [342], TaMo [343,344], and Pt-Ru [345]. Binary metal alloys have been studied to achieve tunable work function over a wide range.…”

“…[263][264][265], conducting metal nitrides (WN x , TiN x , HfN x , MoN x , TaN x , TaSi x N y , etc.) [266][267][268][269][270], alloyed metals [271][272][273], conductive metal oxides (RuO 2 , IrO 2 , etc.) [274,275], nitride alloyed metals [276][277][278], and alloyed FUSI [279][280][281].…”

Composition and crystallography dependence of the work function: Experiment and calculations of Pt-Al alloys

“…[14][15][16][17] or on Hf-based dielectrics (Refs. [18][19][20][21]. Due to significant thermal stability concerns, 22 metal alloys are usually not considered as candidates for high-temperature (∼1000 • C) process flows (the gate-first approach), where alternatives such as ultrathin dielectric capping layers 23,24 and/or refractory metal nitrides 25,26 are employed for EWF tuning.…”

Thermal stability of hafnium and hafnium nitride gates on HfO2 gate dielectrics

“…The three key points for selection of gate electrode materials are work function, thermal stability, and lower resistivity. So far, many types of materials have been investigated to replace poly-silicon, such as pure metals [2][3][4][5][6], binary alloys [7][8][9][10], metal nitrides [11][12][13][14][15], metal carbides [16], and fully silicided Si (FUSI) [17][18][19][20]. Of these, the refractory transition metal nitrides are of interest owing to their good thermal stability, good oxygen diffusion barrier characteristics, and tunable work function.…”