Physical and electrical properties of metal gate electrodes on HfO2 gate dielectrics

Abstract

As the metal-oxide-semiconductor field-effect transistor ͑MOSFET͒ gate lengths scale down to 50 nm and below, the expected increase in gate leakage will be countered by the use of a high dielectric constant ͑high-k) gate oxide. The series capacitance from polysilicon gate electrode depletion significantly reduces the gate capacitance as the dielectric thickness is scaled to 10 Å equivalent oxide thickness ͑EOT͒ or below. Metal gates promise to solve this problem and address other gate stack scaling concerns like boron penetration and elevated gate resistance. Extensive simulations have shown that the optimal gate work functions for the sub-50 nm channel lengths should be 0.2 eV below ͑above͒ the conduction ͑valence͒ band edge of silicon for n-type MOSFETs (p-type MOSFETs͒. This study summarizes the evaluations of TiN, Ta-Si-N, WN, TaN, TaSi, Ir, and IrO 2 as candidate metals for dual-metal gate complementary metal-oxide semiconductor using HfO 2 as the gate dielectric. The gate work function was determined by fabricating metal-oxidesemiconductor capacitors with varying dielectric thicknesses and different post-gate anneals. The metal-dielectric compatibility was studied by annealing the gate stacks at different temperatures. The gate stacks were characterized using transmission electron microscopy, secondary ion mass spectroscopy, Rutherford backscattering spectroscopy, atomic force microscopy, and x-ray diffraction. Based on work functions and thermal stability, Ta-Si-N and TaN show the most promise as metal electrodes for HfO 2 n-MOSFETs.

Deposition of Niobium Nitride Thin Films from Tert‐Butylamido‐Tris‐(Diethylamido)‐Niobium by a Modified Industrial MOCVD Reactor

“…For pFET a work function of 5.15 eV needs to be achieved in order to meet the requirements as a gate electrode. [51] Up to now, however, very little is known about the use of MOCVDgrown niobium nitride thin films as a gate electrode material. [48][49][50] In this work, we report the first data on a NbN/SiO 2 /p-Si gate stack fabricated using the MOCVD of niobium nitride from TBTDEN/ammonia.…”

Annealing-induced Interfacial Reactions between Gate Electrodes and HfO2/Si Gate Stacks Studied by Synchrotron Radiation Photoemission Spectroscopy

“…To solve these problems, the introduction of metal gate electrodes is required. As the candidates of metal gate electrodes, high melting point metals, metal silicides, and metal nitrides have been proposed [10]. However, the interfacial reactions may degrade device performances for metal gate electrodes just like the poly-Si gate electrodes.…”

Atomic layer deposition of TaN and Ta3N5 using pentakis(dimethylamino)tantalum and either ammonia or monomethylhydrazine

“…However, the resistivity of the barrier layer becomes less important as the dimensions of the interconnects are reduced, therefore, Ta 3 N 5 may become advantageous in the future [5]. In addition to its use as a diffusion barrier, TaN x has many other applications, for example, conductive TaN has been investigated as a gate electrode [17][18][19], a work function tuning layer [20], thin film resistors [21], and as a non-magnetic interlayer in non-volatile magnetic random access memory (MRAM) [22]. Ta 3 N 5 has been used in photonic structures, such as inverse opals because of its high refractive index (3) and partial transparency in the visible wavelengths [23].…”