A highly sensitive ISFET using pH-to-current conversion for real-time DNA sequencing

In this paper we present a new sensing concept for ISFET based on pH-to-current conversion. The high sensitivity of our proposed pH-to-current ISFET is achieved by optimally biased ISFET. Analytical models for ISFET sensitivity are used to determine its optimum bias point. Based on SPICE simulations, it is shown that for a minimum size N-type ISFET (W/L=2) using TSMC's 0.25um fabrication process, we can achieve the sensitivity of about 10uA of current change per unit change of pH. A test chip was designed and fabricated using TSMC's 0.25um technology to verify this novel concept. The test result verifies the pH-current sensing concept.