Competitive interplay of deposition and etching processes in atomic layer growth of cobalt and nickel metal films
- PDF / 576,549 Bytes
- 10 Pages / 584.957 x 782.986 pts Page_size
- 68 Downloads / 205 Views
ARTICLE Competitive interplay of deposition and etching processes in atomic layer growth of cobalt and nickel metal films Alexander Sasinska,b) Jennifer Leduc,b) Michael Frank, Lisa Czympiel, and Thomas Fischer Institute of Inorganic Chemistry, University of Cologne, Cologne D-50939, Germany
Silke H. Christiansen Institute of Nanoarchitectures for Energy Conversion, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin D-14109, Germany; and Physics Department, Freie Universität Berlin, Berlin D-14195, Germany
Sanjay Mathura) Institute of Inorganic Chemistry, University of Cologne, Cologne D-50939, Germany (Received 26 June 2018; accepted 20 September 2018)
Atomic layer deposition (ALD) of air stable cobalt and nickel complexes based on tridentate enaminones N,N-(4,4,4-trifluorobut-1-en-3-on)-dimethylethyldiamine (Htfb-dmeda) and N,N-(4,4,4-trifluorobut-1-en-3-on)-dimethylpropyldiamine (Htfb-dmpda) successfully produced metallic cobalt and nickel thin films. Detailed X-ray photoelectron spectroscopy (XPS) studies on the binding interaction of the first precursor monolayer with the surface functional groups elucidated the chemisorption behavior of the new precursor systems. A reactive remote hydrogen plasma was used as the co-reactant to activate the precursor decomposition yielding metal hydroxide intermediates. Subsequent hydrogen plasma etching of as-deposited films resulted in phase-pure metallic films through a recrystallization process, verified by surface and sub-surface XPS. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses revealed pinhole-free films, with low surface roughness (0.2 6 0.06 nm root mean square, RMS) for both, cobalt and nickel thin films. Herein, the competitive role of hydrogen as etchant and reactant was demonstrated as prolonged plasma exposure time periods resulted in the formation of metal hydrides. This is mostly due to the catalytic dissociation of molecular hydrogen on transition metal surfaces, which already occurs upon low energy input.
I. INTRODUCTION
The applicability of metallic cobalt and nickel thin films is growing, resulting in an enhanced research interest concerning the fabrication of pinhole-free homogeneous layers. Ferromagnetic cobalt and nickel layers recently paved the way for spintronic applications,1,2 harnessing the dependence of the electrical resistance from an external magnetic field. Their capacity to eliminate hydrogen radicals on their surface make them excellent catalysts for the growth of graphene.3,4 In addition, they are used as anode materials for solid oxide fuel cells,5,6 as well as for the fabrication of interconnect materials in CMOS devices.7 Constant miniaturization of devices and at the same time aiming for an increasing device performance lead to challenges in thin film engineering. In comparison to other commonly used vapor phase deposition methods, such as chemical vapor deposition (CVD) or physical vapor deposition (PVD), atomic layer deposition (ALD) offers superior step coverage and control over film thickness at a)
Data Loading...
