Influence of thermal annealing on MIM and MIS structures with Al2O3 and a-HIZO deposited at low temperature

The electrical properties of metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) capacitors fabricated with alumina (Al
2
O
3
) as insulating layer and amorphous Hafnium-Indium-Zinc Oxide (a-HIZO) as semiconductor, are investigated. The a-HIZO layer was deposited at room temperature by radio frequency magnetron sputtering, while Al
2
O
3
was deposited at low temperature by atomic layer deposition. A thermal annealing process was applied in different stages of the devices fabrication sequence, where the an oxygen environment improves the electrical characteristics of the capacitor. The dielectric constant of the Al
2
O
3
layer was around 7 at a measurement frequency of 10 kHz. The effective density of charged interface states was in the order of 2.SX10
¹²
cm
⁻²
, The electrical characteristics from fabricated MIS capacitors indicate that these can be used as gate structure of amorphous oxide semiconductor thin film transistors (AOSTFTs) operating in a low voltage range.