Self-cleaning and surface chemical reactions during hafnium dioxide atomic layer deposition on indium arsenide

Rainer Timm,Johan V Knutsson,Martin Hjort,Andrea Troian,Sarah R Mckibbin,Anders Mikkelsen,Samuli Urpelainen,Olof Persson,Joachim Schnadt,Ashley R Head,Sofie Yngman,Jan Knudsen

doi:10.1038/s41467-018-03855-z

Rainer Timm, Johan V Knutsson + Show 10 more

Open Access

https://doi.org/10.1038/s41467-018-03855-z

Copy DOI

Abstract

Atomic layer deposition (ALD) enables the ultrathin high-quality oxide layers that are central to all modern metal-oxide-semiconductor circuits. Crucial to achieving superior device performance are the chemical reactions during the first deposition cycle, which could ultimately result in atomic-scale perfection of the semiconductor–oxide interface. Here, we directly observe the chemical reactions at the surface during the first cycle of hafnium dioxide deposition on indium arsenide under realistic synthesis conditions using photoelectron spectroscopy. We find that the widely used ligand exchange model of the ALD process for the removal of native oxide on the semiconductor and the simultaneous formation of the first hafnium dioxide layer must be significantly revised. Our study provides substantial evidence that the efficiency of the self-cleaning process and the quality of the resulting semiconductor–oxide interface can be controlled by the molecular adsorption process of the ALD precursors, rather than the subsequent oxide formation.

Highlights

Atomic layer deposition (ALD) enables the ultrathin high-quality oxide layers that are central to all modern metal-oxide-semiconductor circuits
As the removal of the native oxide on the indium arsenide (InAs) surface is a central feature of the ALD process, we begin by monitoring this process during the first deposition of TDMA-Hf and follow the time evolution of the arsenic (As) 3d core level spectra, which has a clear signature of both As bound to oxygen and As bound in the InAs crystal
The X-ray photoelectron (XP) spectra reveal a complete removal of the As-oxide component (Fig. 1a) within a timeframe of about 20 s (Fig. 1b)

Summary

Introduction

Atomic layer deposition (ALD) enables the ultrathin high-quality oxide layers that are central to all modern metal-oxide-semiconductor circuits. One key challenge in using these materials is the detrimental effect of high interface trap densities, which are caused by unwanted oxides, atomic vacancies, dimers, or other atomic-scale interface defects[5,6,7] formed during device fabrication These can in particular limit the performance of nanoscale metal-oxidesemiconductor field effect transistors (MOSFETs), which critically relies on the structural quality of the semiconductor–oxide interface[1,2]. HfO2 can be deposited using ALD by first exposing the substrate to a pulse of tetrakisdimethylamido-hafnium (TDMA-Hf), to a pulse of water, and repeating this alternating process to produce homogeneous high-k oxide films of atomic monolayer precise thickness During this ALD process, unwanted native oxides are near-completely removed via the so-called selfcleaning effect[9,14,15,16,17,18,19,20]. The reason for this limitation is mainly the millisecond timescales and the millibar pressure range of typical ALD setups, which are not amenable to either conventional XPS instrumentation that requires ultra-high vacuum (UHV) conditions or FTIR, which has longer measurement times and will be dominated by the gas in the chamber

Methods

Results

Conclusion