Characterizations of single gate and multi-finger gate of ISFET for pH sensor applications

This paper discuss the characterization and the performance of two types of ISFET, which have different gate design. Isfet5 has single gate while Isfet7 has multi-finger gate. The characterization of ISFET is analyzed from the ldVd and ldVg curve, and by measuring the threshold voltage, Vth and response-time of ISFET in order to determine the sensitivity of ISFET. Beside, the hysteresis of ISFET is also measured during the experiment. The Vth value extracted from IdVg curve shows that Isfet7 has higher sensitivity compared to Isfet5. While from the response-time, Isfet5 has better sensitivity than Isfet7. In term of hysteresis effect, Isfet7 has less effect of hysteresis compared to Isfet5. However, from the correlation between sensitivity and pH value graph, based on Vth value and response-time, both graphs conclude that Isfet5 has more linear profile with regression value, R(2) more than 0.9960.