High‐density remote plasma sputtering of high‐dielectric‐constant amorphous hafnium oxide films. Issue 5 (4th March 2013)

• Record Type: Journal Article
• Authors: Li, Flora M.; Bayer, Bernhard C.; Hofmann, Stephan; Speakman, Stuart P.; Ducati, Caterina; Milne, William I.; Flewitt, Andrew J.
• Is Part Of: Physica status solidi. Volume 250:Issue 5(2013:May)
• Page Start: 957
• Page End: 967
• Publication Date: 2013-03-04
• Subjects: Solid state physics -- Periodicals; Solids -- Periodicals; Atomic structure -- Periodicals; 530.41
• DOI: 10.1002/pssb.201248520
• Languages: English
• ISSNs: 0370-1972

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p> <boxed-text content-type="graphic" position="anchor" orientation="portrait"> <graphic position="anchor" mimetype="image" xlink:href="ark:/27927/pgg1zvp9zp4" orientation="portrait" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /> </boxed-text> </p> <p>Hafnium oxide (HfO<sub><italic>x</italic></sub>) is a high dielectric constant (<italic>k</italic>) 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<sub><italic>x</italic></sub> while maintaining a high dielectric constant. A technique called high target utilization sputtering (HiTUS) is demonstrated to be capable of depositing high‐<italic>k</italic> amorphous HfO<sub><italic>x</italic></sub> 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<sub><italic>x</italic></sub> thin films have been deposited at a rate of ∼1.6 nm min<sup>−1</sup> at room temperature, with a resistivity of 10<sup>13</sup> Ω cm, a breakdown strength of 3.5 MV cm<sup>−1</sup> and a dielectric constant of ∼18.2. By comparison, using the HiTUS process, amorphous HfO<sub><italic>x</italic></sub> (<italic>x</italic> = 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<sup>−1</sup> with a high resistivity of 10<sup>14</sup> Ω cm, a breakdown strength of 3 MV cm<sup>−1</sup> and a high dielectric constant of ∼30. Two key conditions must be satisfied in the HiTUS system for high‐<italic>k</italic> HfO<sub><italic>x</italic></sub> 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<sub><italic>x</italic></sub> is very attractive as a dielectric material for large‐area electronic applications on flexible substrates.</p> </abstract>