Ultrahigh-Sensitive and CMOS Compatible ISFET Developed in BEOL of Industrial UTBB FDSOI

The industrialization of ion-sensitive field-effect transistors (ISFETs) has been constrained due mainly to the limited sensitivity, and inclusion of bulky reference electrode. With this paper, we report an ultrahigh-sensitive and CMOS compatible ISFET in which the need for the reference electrode is eliminated. Based on an industrial UTBB FDSOI device in BEOL, we obtained an ultrahigh sensitivity of 730 mV/pH which is 12-times higher than the Nernst limit. Integrating the sensing area and the control gate in the BEOL of UTBB FDSOI transistors with a capacitive divider circuit, and using the back biasing feature of such devices, we could eliminate the necessity of the reference electrode making our sensor highly scalable and ideal for the IoT. This is the first demonstration of an integrated pH sensor in the BEOL of FDSOI platform. The measurements on fabricated sensors have also been validated by modeling and simulation.