Drift and hysteresis effects improved by RTA treatment on hafnium oxide in pH-sensitive applications

Rapid thermal annealing (RTA) treatment in N2 ambient is applied to optimize the drift and hysteresis effects of Hf O2 -based sensing membrane. The drift coefficient of the 8 nm thick Hf O2 -electrolyte-insulator-semiconductor (EIS) structure was 1.4 mVh. After being treated with RTA at 900°C, the drift coefficient and hysteresis width of the 8 nm thick Hf O2 layer was reduced to 0.65 mVh and 1.7 mV, respectively. For the Hf O2 -EIS structure treated with RTA at 500°C, the drift coefficient was increased to 3.25 mVh because of the crystallization of the Hf O2 layer and was improved by 900°C annealing due to the densification of the Hf O2 layer. Therefore, the drift coefficient of the Hf O2 -EIS structure was reduced to 0.65 mVh by RTA treatment at 900°C. With excellent pH sensitivity and stability, an Hf O2 layer with proper RTA processing can be used as pH sensing material in ion-sensitive field-effect transistor-type sensors. Moreover, to easily control capacitance-voltage measurements and automatically calculate parameters such as pH sensitivity, drift coefficient, and hysteresis width of an Hf O2 -EIS structure, a program based on LabVIEW was developed.