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Hot‐wire assisted ALD of tungsten films: In‐situ study of the interplay between CVD, etching, and ALD modes
Author(s) -
Yang Mengdi,
Aarnink Antonius A. I.,
Kovalgin Alexey Y.,
Wolters Rob A. M.,
Schmitz Jurriaan
Publication year - 2015
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201532305
Subject(s) - tungsten , x ray photoelectron spectroscopy , materials science , chemical vapor deposition , etching (microfabrication) , atomic layer deposition , hydrogen , fluorine , analytical chemistry (journal) , raman spectroscopy , nanotechnology , chemical engineering , thin film , chemistry , metallurgy , optics , organic chemistry , physics , layer (electronics) , engineering
In this work, we investigated an approach of hot‐wire assisted ALD (HWALD), utilizing a hot (up to 2000 °C) tungsten (W) wire. Tungsten films were deposited by this method using alternating pulses of WF 6 gas and atomic hydrogen (at‐H). The latter was generated by catalytic dissociation of molecular hydrogen (H 2 ) upon the hot‐wire. The W films were grown on a 100‐nm thick thermal SiO 2 . The growth process was monitored in real time by an in‐situ spectroscopic ellipsometer (SE). The real‐time SE monitoring revealed the coexistence of three processes: CVD, etching, and ALD of the W film. WF 6 could back‐stream diffuse to the hot‐wire, resulting in WF 6 decomposition and generation of a flux of fluorine (F). The latter caused etching of the grown W film and the filament, and provided extra tungsten supply, which might cause CVD. Higher pressure and higher carrier gas flow rate were found to largely suppress the back‐stream diffusion of WF 6 , which efficiently limited CVD. By controlling the dose of WF 6 and process pressure, the etching had also been minimized. X‐ray photoelectron spectroscopy of optimized HWALD grown W revealed 99 at% of W; concentrations of oxygen and fluorine were lower than 1%, below the detection limit.