Impact of deposition and annealing temperature on material and electrical characteristics of ALD HfO2

Hafnium oxide (HfO2) is one of the most promising high-k materials to replace SiO2 as a gate dielectric. Here we report material and electrical characterization of atomic layer deposition (ALD) hafnium oxide and the correlations between the results. The HfO2 films were deposited at 200, 300, or 370degreesC and annealed in a nitrogen ambient at 550. 800, and 900degreesC. Results indicate that deposition temperature controls both the material and the electrical properties. Materials and electrical properties of films deposited at 200degreesC are most affected by annealing conditions compared to films deposited at higher temperatures. These films are amorphous as deposited and become polycrystalline after 800degreesC anneals. Voids are observed after a 900degreesC anneal for the 200degreesC deposited films. The 200degreesC deposited films have charge trapping and high leakage current following anneals at 900degreesC. The 300degreesC deposited films have lower chlorine content and remain void-free following high-temperature anneals. These films show a thickness-dependent crystal structure. Annealing the films reduces leakage current by four orders of magnitude. Finally, films deposited at 370degreesC have the highest density, contain the least amount of impurities, and contain more of the monoclinic phase of HfO2 than those deposited at 300 and 200degreesC. The best electrical performance was obtained for films deposited at 370degreesC. (C) 2004 The Electrochemical Society.