Atomic Layer Deposition of Cobalt Silicide Thin Films Studied by in Situ Infrared Spectroscopy

Abstract

Atomic layer deposition of cobalt silicide (CoSi 2 ) thin films on H-terminated Si(111) surfaces, using the cobaltbased precursor tertiarybutylallylcobalttricarbonyl ( t Bu-AllylCo-(CO) 3 ) and trisilane, is investigated by in situ Fourier transform infrared spectroscopy (FTIR) and ex situ X-ray photoelectron spectroscopy (XPS) to uncover the film growth mechanisms. The strong reactivity of t Bu-AllylCo(CO) 3 with H-terminated silicon surfaces and inertness with silicon oxide surfaces, as previously determined by IR spectroscopy [Chem. Mater. 2012, 24, 1025, opens the door for selective deposition. Deposition of CoSi 2 is observed after a brief nucleation period (∼3 cycles), during which the stabilization of the cobalt precursor takes place, as evidenced by a shift of the stretch frequency of the carbonyl groups bonded to the Co center from 2010 to 1980 cm −1 . This shift is evidence for completion of the catalytic reaction and leads to a surface termination and configuration that is favorable for subsequent ligand exchange with trisilane, fostering a classical ligand-exchange ALD growth. In steady state, the CoSi 2 growth rate is 0.15 ± 0.05 Å per cycle, as measured by Rutherford backscattering spectroscopy (RBS). XPS measurements with depth profiling indicate that the CoSi 2 film is stoichiometric with negligible carbon contamination.

Atomic Layer Deposition of CoxOy Films: Oxidants versus Composition

“…Multiple Co precursors, such as oxygen‐coordinated compounds, [ 8 ] halides, [ 9 ] organometallics, [ 10 ] carbonyl complexes, [ 11 ] as well as nitrogen‐coordinated precursors, [ 12 ] have already been utilized to deposit binary Co oxide films by ALD. Most of the above precursors exhibit poor reactivity with water (H 2 O) oxidant, instead, they prefer to react with either oxygen plasma or ozone (O 3 ), leading to ligands combustion and loss of control over the oxidation state.…”

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Recently, the atomic layer deposition (ALD) technique has been increasingly applied in the design and synthesis of novel film systems due to it offers high reproducibility and precise control over their composition, thickness, and microstructure, making it great potential for the deposition of high-quality Co x O y films. [7] Multiple Co precursors, such as oxygen-coordinated compounds, [8] halides, [9] organometallics, [10] carbonyl complexes, [11] as well as nitrogen-coordinated precursors, [12] have already been utilized to deposit binary Co oxide films by ALD. Most of the above precursors exhibit poor reactivity with water (H 2 O) oxidant, instead, they prefer to react with either oxygen plasma or ozone (O 3 ), leading to ligands combustion and loss of control over the oxidation state.

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Chemistries and Surface Reaction Mechanisms at the Initial Stages of Plasma-Enhanced Atomic Layer Deposition of Ru and Co on Silicon Substrate

“…One solution to these critical issues is to replace copper with alternative metals that do not suffer from these issues. In this regard, the early transition metals Ruthenium [5][6][7] (Ru) and Cobalt [8][9][10][11] (Co) are of high interest as alternative materials for replacing Cu in next generation interconnects.…”

Density Functional Theory Study of the Adsorption and Dissociation of Copper(I) Acetamidinates on Ni(110): The Effect of the Substrate

“…The characterization of surface reaction mechanisms is difficult, but has recently been aided by research using surface-sensitive spectroscopies methods. ,,, We and other groups have employed techniques such as infrared absorption spectroscopy, − photoelectron spectroscopy (X-ray photoelectron spectroscopy –XPS– and ultraviolet photoelectron spectroscopy –UPS–), ,− X-ray absorption spectroscopy (XAS), temperature-programed desorption (TPD) ,− and other mass-spectrometry detection arrangements, − (including secondary ion mass spectrometry –SIMS– , and molecular beams − ), and quartz crystal microbalance (QCM) measurements ,− to interrogate the several steps of this chemistry. In general, it has been found that some of the chemical routes that metalorganic compounds follow on surfaces are analogous to those well-documented for discrete metal complexes in solution.…”