The fabrication of ion sensitive field effect transistors (ISFET) and microelectrode arrays for use as chemical sensors using a commercial CMOS fabrication process is described. The commercial technology is readily available through the Canadian Microelectronics Corporation; however, several of the recommended design rules must be ignored in preparing chemical sensors using this process. The ISFET devices show near theoretical response to K+ in aqueous solution (55 mV slope) when coated with a K+ sensitive membrane. An extended gate ion sensitive device is presented which offers advantages in encapsulation of ISFET sensors. The source-drain current of both devices show a linear response to log [Formula: see text] in contrast to ISFETs previously reported that have high internal lead resistances. Al and poly-Si microelectrode arrays are fabricated commercially and then Pt is electrodeposited on the microelectrodes. The resulting arrays show good cyclic voltammetric response to Fe(CN)64− and Ru(NH3)63+ and are relatively durable.
Material and process limits in silicon VLSI technology