Microstructures of HfOx Films Prepared via Atomic Layer Deposition Using La(NO3)3·6H2O Oxidants.

Sejong Seong,Jinho Ahn,Taehoon Lee,Seon Yong Kim,Yong Chan Jung,In-Sung Park

doi:10.3390/ma14237478

Sejong Seong, Jinho Ahn + Show 4 more

Open Access

https://doi.org/10.3390/ma14237478

Copy DOI

Abstract

Hafnium oxide (HfOx) films have a wide range of applications in solid-state devices, including metal–oxide–semiconductor field-effect transistors (MOSFETs). The growth of HfOx films from the metal precursor tetrakis(ethylmethylamino) hafnium with La(NO3)3·6H2O solution (LNS) as an oxidant was investigated. The atomic layer deposition (ALD) conditions were optimized, and the chemical state, surface morphology, and microstructure of the prepared films were characterized. Furthermore, to better understand the effects of LNS on the deposition process, HfOx films deposited using a conventional oxidant (H2O) were also prepared. The ALD process using LNS was observed to be self-limiting, with an ALD temperature window of 200–350 °C and a growth rate of 1.6 Å per cycle, two times faster than that with H2O. HfOx films deposited using the LNS oxidant had smaller crystallites than those deposited using H2O, as well as more suboxides or defects because of the higher number of grain boundaries. In addition, there was a difference in the preferred orientations of the HfOx films deposited using LNS and H2O, and consequently, a difference in surface energy. Finally, a film growth model based on the surface energy difference was proposed to explain the observed growth rate and crystallite size trends.

Highlights

IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
Nanocrystalline hafnium oxide (HfOx) films were successfully synthesized by atomic layer deposition (ALD) using La(NO3)3·6H2O solution (LNS)
The XRD results demonstrated that the HfOx films deposited with either LNS or H2 O both consisted of the monoclinic phase, but there was a difference in the orientation preference

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. With the continued reduction in size and increase in complexity of semiconductor devices, a need for the fabrication of ultrathin films with precisely controlled thickness on three-dimensional device structures is becoming apparent To meet this requirement, atomic layer deposition (ALD) is one possible thin film fabrication method [5]. To enhance the throughput of the ALD method, many studies have been focused on developing batch-type ALD and spatial ALD [7,8] Both metal precursors and oxidants can modulate the characteristics of metal oxide films; that is, the choice of these materials influences the growth rate, ALD temperature window, crystalline structure, contamination, and dielectric and electrical properties. A deposition mechanism was proposed to explain the difference between the growth properties and microstructures of HfO2 films fabricated using the La(NO3 )3 ·6H2 O solution and H2 O

HfOx Film Fabrication

Analyses of HfOx Thin Films Properties

Results and Discussion

Chemical

Relationship

Schematic

Conclusions