Hysteresis-free HfO2 film grown by atomic layer deposition at low temperature

Hysteresis-free hafnium oxide films were fabricated by atomic layer deposition at 90°C without any post-deposition annealing, and their structures and properties were compared with films deposited at 150°C and 250°C. The refractivity, bandgap, dielectric constant and leakage current density all increase with deposition temperature, while the growth rate and breakdown field decrease. All films are amorphous with roughly the same composition. Although the thin films deposited at the above-mentioned temperatures all show negligible hysteresis, only the 90°C-deposited films remain hysteresis-free when the film thickness increases. The 90°C-deposited films remain hysteresis-free after annealing at 300°C. The hysteresis in films deposited at high temperatures increases with deposition temperature. Evidences show such hysteresis originates in the HfO2 film instead of the interface. Based on a careful structure analysis, middle-range order is suggested to influence the trap density in the films. HfO2 films deposited at low temperature with negligible hysteresis and excellent electrical properties have great potential for the fabrication and integration of devices based on non-silicon channel materials and in applications as tunneling and blocking layers in memory devices.