Ion sensing improvements of hafnium oxide by nitrogen incorporation

This is the first time that hafnium oxynitride (HfO/sub x/N/sub y/) have been applied to hydrogen ion sensing technology. HfO/sub x/N/sub y/ and HfO/sub 2/ were prepared in different ratio Ar/N/sub 2//O/sub 2/ gas mixture by sputter with hafnium target. The sensitivity for all samples could be improved for at least 3.3mV/pH by 12 hours R.O. water immersion. The optimized condition for HfO/sub x/N/sub y/-EIS was sputtering in the ambient of N/sub 2/ ratio 10% and achieved highest sensitivity (56.64mV/pH) and lowest drift (1.42mV/hr) and hysteresis (1.7mV). This material and process could also improve membrane thermal stability and integrate easily with standard CMOS process.