High‐density remote plasma sputtering of high‐dielectric‐constant amorphous hafnium oxide films

Abstract

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 À1 at room temperature, with a resistivity of 10 13 V cm, a breakdown strength of 3.5 MV cm À1 and a dielectric constant of $18.2. By comparison, using the HiTUS process, amorphous HfO x (x ¼ 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 À1 with a high resistivity of 10 14 V cm, a breakdown strength of 3 MV cm À1 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 cubiclike short range order. This HfO x is very attractive as a dielectric material for large-area electronic applications on flexible substrates.

ALD preparation of high-k HfO2 thin films with enhanced energy density and efficient electrostatic energy storage

“…27,28 The maximum dielectric constant at 1 MHz is about 26 obtained for the 63 nm HfO 2 lms, which is comparable with that reported in the literature. 29 The dielectric loss was maintained at a low level of below 0.1 in the measured frequency range for all the samples. Fig.…”

Analysis of amorphous indium-gallium-zinc-oxide thin-film transistor contact metal using Pilling-Bedworth theory and a variable capacitance diode model

“…metals appears similar but with a wide range of depletion widths; consistent with a hyper abrupt p-n junction, where the capacitance is inversely proportional to the square root of the bias-voltage (V BIAS ) and to the channel width (W). 20,[29][30][31] This behaviour resembles that of a variable diode capacitor (varactor). Therefore, mono metal diffusion as depicted by the "Pilling-Bedworth" theory causes a variable capacitance to exist within the TFTs with applied bias.…”

High‐Mobility ZnO Thin Film Transistors Based on Solution‐processed Hafnium Oxide Gate Dielectrics

“…Amongst high‐ k dielectrics that include a wide range of transition metals and rare earth metal oxides, hafnium oxide (HfO 2 ) is one of the most extensively studied material as a gate dielectric due to its high dielectric constant and wide band gap. HfO 2 thin films can be grown using a wide range of vacuum based deposition techniques namely the atomic layer deposition (ALD), chemical vapor deposition (CVD), magnetron sputtering, pulsed laser deposition (PLD) and molecular beam epitaxy (MBE) . HfO 2 films deposition from solutions have also been reported .…”