The Preparation And Electrical Properties Of HfO₂High-k Gate Dielectric Thin Films

The continued scaling down of complementary metal oxide semiconductor (CMOS) technology is making the conventional gate dielectrics SiO2reach its physical limit due to its unacceptable tunneling current and intrinsic reliability. Using a new material with a dielectric constant larger than that of SiO2to replace SiO2film as gate dielectric is an indispensable task. Among these potential high-k dielectric materials, HfO2is always keeping the interest for people whether in fundamental research or industrial application in these years because of its relatively high dielectric constant (k～25), large band gap (>5eV) and reasonable band gap offsets with silicon(>1eV).In this research, HfO2films were deposited by magnetron sputtering and prepared to Pt/HfO2/Si or TiN/HfO2/Si MOS capacitors by using Pt or TiN as metal electrode. We investigated the effect of long annealing, rapid thermal annealing(RTA) and sputtering atmosphere for different nitrogen argon ratio or oxygen argon ratio on the structure and electrical properties of HfO2thin films. The electrical properties of HfO2thin films were improved by annealed for30min or RTA for60s at different temperatures. The sample annealed for30min at500℃was amorphous and had larger dielectric constant, smaller equivalent oxide thickness and lower leakage current density than those annealed at other temperatures. HfO2thin films rapid thermal annealed for60s were crystalline, which caused leakage current density increasing, and the sample rapid thermal annealed for60s at600℃had bigger dielectric constant than other temperatures. Compared to RTA for60s at500℃, HfO2film annealed for30min at500℃improved the defects in the film, maintained the amorphous structure, had smaller surface roughness and better electrical properties. With same annealing conditions, HfO2films had better electricity performance with TiN electrode than Pt electrode. Sputtering access to different argon and nitrogen flow and fixed work pressure, HfO2films were also amorphous. When Ar/N2flow ratio was15/30sccm, HfO2film had the largest dielectric constant(16.9) and smallest leakage current density(1.6×10-7A/cm2). Sputtering with fixed argon flow and changed nitrogen or oxygen flow, HfO2film had the best electrical performance when Ar/N2or Ar/O2flow ratio was30/5sccm.