Patent ID: 6897081

Claim:
A method for fabricating a monolithic chip including multi-sensors that can detect pH, temperature, photo-intensity simultaneously and a readout circuit, comprising the steps: forming an ion sensitive field effect transistor (ISFET) with an extended gate sensitive window and coating an SnO 2 sensitive membrane on the window using sputtering process, so as to form an extended gate field effect transistor (EGFET) as an ion sensitive sensor (pH sensor); forming a metal oxide semiconductor field effect transistor (MOSFET), wherein an integrated readout circuit with selective switches are implemented to sequentially output values sensed by the multi-sensors; layouting an N-type well over a P-type substrate and then a p-diffusion region within the N-type well using ion implanting process to form a temperature diode consisting of the p-diffusion region with respect to the N-type well, such that the temperature diode acts as a temperature sensor to sense temperature in forward bias voltage; and forming an n-diffusion region within the P-type substrate using the ion implanting process, such that a photodiode consisting of the n-diffusion region with respect to the P-type substrate is produced and acts as a photo-sensor to sense photo-intensity in reverse bias voltage.