ISFET threshold voltage programming in CMOS using hot-electron injection

The use of hot-electron injection as a method for programming the threshold voltages of CMOS based ion-sensitive field-effect transistors (ISFETs) in standard pH buffer solution is presented. This method allows compensation of large threshold voltage variations generally seen with ISFETs fabricated in unmodified CMOS due to the presence of trapped charge, enabling operation of the device using nominal supply voltage as well as reduction of mismatch between devices when fabricating ISFET arrays. Fabricated in a 0.35 m CMOS process, threshold voltage shifts of up to 2.8 V have been achieved in a pH 7 buffer solution.