Influence of rapid thermal annealing temperature on structure and electrical properties of high permittivity HfTiO thin film used in MOSFET

• Improved microstructure and electrical properties of HfTiO film by RTA at 500 °C.
• The largest k value of 44.0 and the lowest leakage current of 1.81 × 10−7 A/cm2.
• Fabricate a MOSFET showing a good transistor performance.

HfTiO thin films were prepared by r.f. magnetron co-sputtering on Si substrate. To improve the electrical properties, HfTiO thin films were post heated by rapid thermal annealing (RTA) at 400 °C, 500 °C, 600 °C and 700 °C in nitrogen. It was found that the film is amorphous below 700 °C and at 700 °C monoclinic phase HfO2 has occurred. With the increase of the annealing temperature, the film becomes denser and the refractive index increases. By electrical measurements, we found at 500 °C annealed condition, the film has the best electrical property with the largest dielectric constant of 44.0 and the lowest leakage current of 1.81 × 10−7 A/cm2, which mainly corresponds to the improved microstructure of HfTiO thin film. Using the film annealed at 500 °C as the replacement of SiO2 dielectric layer in MOSFET, combining with TiAlN metal electrode, a 10 μm gate-length MOSFET fabricated by three-step photolithography processes. From the transfer (IDS–VG) and output (IDS–VDS) characteristics, it shows a good transistor performance with a threshold voltage (Vth) of 1.6 V, a maximum drain current (Ids) of 9 × 10−4 A, and a maximum transconductance (Gm) of 2.2 × 10−5 S.