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High‐density remote plasma sputtering of high‐dielectric‐constant amorphous hafnium oxide films
Author(s) -
Li Flora M.,
Bayer Bernhard C.,
Hofmann Stephan,
Speakman Stuart P.,
Ducati Caterina,
Milne William I.,
Flewitt Andrew J.
Publication year - 2013
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201248520
Subject(s) - amorphous solid , materials science , dielectric , high κ dielectric , hafnium , thin film , sputtering , nanocrystalline material , sputter deposition , gate dielectric , analytical chemistry (journal) , thin film transistor , optoelectronics , composite material , metallurgy , zirconium , nanotechnology , transistor , electrical engineering , crystallography , chemistry , layer (electronics) , engineering , voltage , chromatography
Hafnium oxide (HfO x ) is a high dielectric constant ( k ) oxide which has been identified as being suitable for use as the gate dielectric in thin film transistors (TFTs). Amorphous materials are preferred for a gate dielectric, but it has been an ongoing challenge to produce amorphous HfO x while maintaining a high dielectric constant. A technique called high target utilization sputtering (HiTUS) is demonstrated to be capable of depositing high‐ k amorphous HfO x thin films at room temperature. The plasma is generated in a remote chamber, allowing higher rate deposition of films with minimal ion damage. Compared to a conventional sputtering system, the HiTUS technique allows finer control of the thin film microstructure. Using a conventional reactive rf magnetron sputtering technique, monoclinic nanocrystalline HfO x thin films have been deposited at a rate of ∼1.6 nm min −1 at room temperature, with a resistivity of 10 13 Ω cm, a breakdown strength of 3.5 MV cm −1 and a dielectric constant of ∼18.2. By comparison, using the HiTUS process, amorphous HfO x ( x = 2.1) thin films which appear to have a cubic‐like short‐range order have been deposited at a high deposition rate of ∼25 nm min −1 with a high resistivity of 10 14 Ω cm, a breakdown strength of 3 MV cm −1 and a high dielectric constant of ∼30. Two key conditions must be satisfied in the HiTUS system for high‐ k HfO x to be produced. Firstly, the correct oxygen flow rate is required for a given sputtering rate from the metallic target. Secondly, there must be an absence of energetic oxygen ion bombardment to maintain an amorphous microstructure and a high flux of medium energy species emitted from the metallic sputtering target to induce a cubic‐like short range order. This HfO x is very attractive as a dielectric material for large‐area electronic applications on flexible substrates.