Work function thermal stability of RuO2-rich Ru–Si–O p-channel metal-oxide-semiconductor field-effect transistor gate electrodes

Abstract

We report on thermal stability of the effective work function (EWF) of RuO2-rich Ru–Si–O gate electrodes intended for high-performance p-channel metal-oxide-semiconductor field-effect transistors. The Ru–Si–O thin films, with the composition 15% and 40% of SiO2, were grown by atomic vapor deposition at either 380 or 450°C on SiO2∕Si substrate. The Ru–Si–O thin film with 15% of SiO2 deposited at 450°C was evaluated as the most thermally stable gate electrode showing the EWF of 5.0eV after rapid thermal annealing (RTA) at 800°C∕10s in nitrogen followed by forming gas annealing (FGA). Transmission electron microscopy studies show that Ru–Si–O films are composed of RuO2-rich nanograins embedded in the SiO2-rich amorphous matrix. The Ru–Si–O films show enhanced thermal stability, as we observe reduction of RuO2 to Ru nanograins without disintegration of the layers after RTA at 900°C∕10s and subsequent FGA 430°C∕30min. Resistivity of the Ru–Si–O films as a function of temperature was found to be dependent on composition as well as deposition temperature. Resistivity of the Ru–Si–O film with 15% of SiO2 deposited at 450°C shows metalliclike character with a residual resistivity ratio of 1.3. The effect of RTA and FGA on the resistivity of the Ru–Si–O films is discussed in terms of the increase in connectivity and grain size.

Transparent Amorphous Ru–Si–O Schottky Contacts to In–Ga–Zn–O

“…Schottky barrier heights and ideality factors (n), evaluated by fitting exact solution of Schottky diode equation based on thermionic emission model[16] to experimental I-V curves for Ru-Si-O deposited at %O 2 = 10% and 20% were Φ B = 0.91 eV, n = 1.96 and Φ B = 0.93 eV, n = 1.79, respectively. Taking into account that reported work function of Ru-Si-O and electron affinity of a-IGZO equals 5.3 eV and 4.5 eV respectively, obtained Φ B values are consistent with Schottky-Mott barrier formation model[11],[10].…”

“…It increases from 6.2×10 -4 Ω·cm for oxygen-free films up to 8.5×10 -1 Ω·cm for layers deposited at 30% of O 2 . It may be related to the fact that film-forming oxygen is known to bond mainly with Si, leading to the formation of SiO 2 increasingly surrounding RuO 2 and causing the increase of resistivity [11]. Application of amorphous TCO metallisation prevents drainage of O atoms from subsurface contact region allowing to form Schottky barrier to a-IGZO without additional technological steps i.e.…”

“…According to Schottky-Mott model, potential barrier height (Φ B ) is equal to the difference between work function of metal and electron affinity of n-type semiconductor [10]. Ru-Si-O based metallisation exhibits work function above 5.3 eV, allowing to obtain highly rectifying Schottky contacts to a-IGZO owing to its electron affinity χ IGZO equal to 4.2 eV [11], [12].…”

Atomic Layer Deposition of Ruthenium Thin Films from (Ethylbenzyl) (1-Ethyl-1,4-cyclohexadienyl) Ru: Process Characteristics, Surface Chemistry, and Film Properties

“…10−12 Ru offers a high work function (4.7 eV), a low bulk resistivity (∼7 μΩcm), and high chemical stability. Moreover, Ru forms a conductive oxide, RuO 2 , with a high work function (>5 eV), 13 which avoids the formation of insulating interfacial layers in contact with oxides.…”

Electrical characterization of 4H‐SiC Schottky diodes with RuWOx Schottky contacts before and after irradiation by fast electrons

“…Ruthenium dioxide (RuO 2 ) is an extensively explored material 3, 4 because of its mechanical properties including resistance to abrasion and fatigue, low electrical resistance and high chemical stability. Kim et al 5 found the advantage of using W–RuO 2 contacts for high‐ k dielectric applications.…”