Atomic layer deposition and characterization of stoichiometric erbium oxide thin dielectrics on Si(1 0 0) using (CpMe)3Er precursor and ozone

Runshen Xu,Qian Tao,Yi Yang,Christos G Takoudis

doi:10.1016/j.apsusc.2012.05.019

Abstract

Thin stoichiometric erbium oxide films were atomic layer deposited on p-type Si(100) substrates using tris(methylcyclopentadienyl)erbium and ozone. The film growth rate was found to be 0.12±0.01nm/cycle with an atomic layer deposition temperature window of 170–330°C. X-ray photoelectron spectral (XPS) analysis of the resulting Er2O3 films indicated the as-deposited films to be stoichiometric with no evidence of carbon contamination. Studies of post deposition annealing effects on resulting films structures, interfaces, surface morphologies, and electrical properties were done using Fourier transform infrared spectroscopy, XPS, glancing incidence X-ray diffraction, optical surface profilometry, and C–V/I–V measurements. As-deposited Er2O3 films were found to start crystallizing in the cubic structure with dominant (222) orientation; no erbium silicate was found at the interface. After annealing at 800°C in N2, a new XPS feature was found and it was assigned to the formation of erbium silicate. As the annealing temperature was increased, the interfacial erbium silicate content was found to increase in the temperature range studied. Electrical characterization of Er2O3 thin gate dielectrics annealed at 600°C exhibited higher dielectric constant (κ=11.8) than that of as-deposited films (9.8), and a remarkably low hysteresis voltage of less than 50mV along with a leakage current density of 10−7Acm−2 at 1MVcm−1.

Highlights

Structural and interfacial studies of high dielectric constant (κ) materials are important in the continuous scaling of nanoelectronics such as complementary metal oxide semiconductors and dynamic random-access memories (DRAM).[1]
Er2O3 has been grown with various deposition techniques, such as RF sputtering,[13] electron beam evaporation,[14] metal-organic chemical vapor deposition (MOCVD),[15, 16] and atomic layer deposition (ALD).[7, 17, 18]
Ultrathin Er2O3 films were deposited on p-type Si(100) substrates by atomic layer deposition using tris(methylcyclopentadienyl)erbium and ozone

Summary

Introduction

Structural and interfacial studies of high dielectric constant (κ) materials are important in the continuous scaling of nanoelectronics such as complementary metal oxide semiconductors and dynamic random-access memories (DRAM).[1]. The growth rate was reported to increase with precursor pulse duration, which was likely due to partial thermal decomposition of Er(tBu2amd) during the precursor delivery process; the stoichiometric ratio O/Er of those films was found to be 1.8 with a carbon content of 1.8 % In both studies of β-diketonate and amidinate types of erbium precursors, as-deposited Er2O3 was found to be amorphous at deposition temperatures below 250 °C, but started to crystalize into a polycrystalline cubic structure at a temperature of 250 - 350 °C. Cyclopentadienyl compounds have a relatively low sublimation temperature which leads to a high ALD growth rate due to its moderate vapor pressure.[6, 22] Tris(methylcyclopentadienyl)erbium, (CpMe)3Er, was used with water vapor to deposit Er2O3 thin films on silicon.[18] The deposition rate was reported to be ~ 0.15 nm/cycle at 250 - 350 °C; the resulting films were found to be overstoichiometric (O/Er = 1.7) with a carbon content of ~ 2.5 %. Post deposition annealing temperatures of 600-1000°C are used for studies on the annealing behavior of the resulting ALD films; after annealing, changes in Er2O3 film structure, interfacial layer, and surface morphology are presented and discussed using a variety of analytical techniques

Experimental

Results and Discussion

Conclusion