Novel Al1.997Hf0.003O3 High-k gate dielectric thin films grown by pulsed laser deposition using pre-synthesized target material

Abstract

The present study reported pure pre-synthesized Al1.997Hf0.003O3 target for the formation of novel high-k gate dielectric thin films using pulsed laser deposition technique. High substrate temperature of 800 °C and ultra-high-vacuum condition at 10−8 Torr were used to produce stable hexagonal crystal structure of thin films with exclusive crystal growth directions in the (110) and (024) planes as evidenced by the XRD. AFM images displayed dense and uniform distribution of crystallites with RMS as low as 0.12 nm, contributing to very smooth morphology. Optical observation by the UV–Vis analysis showed that the introduction of Hf in the lattice of the Al2O3 material had significantly modified the energy bands of Al1.997Hf0.003O3, hence, improved k values. Consequently, the C–V measurements of the fabricated thin films based on Pt/Al1.997Hf0.003O3/p-Si MOS capacitor exhibited a high capacitance of ~ 202 nF at ~ 6 nm thickness and attributed to high-k value of ~ 21. The I–V measurements also revealed the electron tunnelling was reduced with thicker films of Al1.997Hf0.003O3, due to this, leakage current density was improved to ~ 10−10 A/cm2. These results revealed that Al2−xHfxO3 thin films could be significant in searching for a replacement dielectric for nanoscale MOS devices.