Polymer-Assisted Deposition of Al-Doped HfO2 Thin Film with Excellent Dielectric Properties

摘要

Demands for high-k dielectric materials increase as transistors scale down. One of the promising high-k dielectric materials is HfO2 owing to its large band gap, high dielectric constant, and excellent physical/chemical stability. Although several cost-effective solution-based deposition methods have been developed, their dielectric performances are inferior to those obtained by vacuum processes (e.g., atomic layer deposition, sputtering). This study demonstrates a solution-based polymer-assisted deposition (PAD) of high-k Al-doped HfO2 thin films exhibiting remarkable dielectric performances comparable to the conventional deposition methods. The PAD ensures the control of film thickness (>= 3 nm) and the homogenous Al doping in the entire thin film. The key to the success is HCl-mediated coordination of metal precursor and polymer. Thorough analysis on the structure and chemical composition of the dielectric layer is carried out. It is found that the phase transition from monoclinic phase to a mixture of tetragonal and amorphous phases results in excellent dielectric properties. The 7.8 nm thick thin film doped with 4.1 at% of Al exhibits a high dielectric constant of 30.2 with a high areal capacitance (674 nF cm(-2) at 1.0 kHz), a low leakage current (3.3 x 10(-9) A cm(-2) at 2.0 MV cm(-1)), and a high breakdown voltage (7.7 V).