Nitrogen effects on the sensitivity of tantalum nitride (TaxN) for ion sensing devices

A novel approach was proposed in this work for hydrogen ion sensing with tantalum nitride (Ta_xN). Ta_xN sensing membrane was sputtered by mixture gas which gas ratio was modified during the sputtering, from 6 to 20 % with Ar and nitrogen mixture gas for tantalum (Ta) target. The optimized condition for Ta_xN-EIS structure improved the sensitivity to 50.47 mV/pH under 16% nitrogen mixture gas ratio. However sensitivity of all nitrogen ratio conditions could be improved for several mV/pH after 8 hours R.O. water immersion. Hysteresis width also changed with different nitrogen ratio and the minimum hysteresis was 5mV/pH at 12% nitrogen ratio. Due to the large variation of sensitivity and high linearity, the nitrogen ratio modification sputtering is suitable for employ TaN to high sensitivity ISFET and low sensitivity REFET application respectively.