An IC structure includes a biologically sensitive field-effect transistor (BioBET) in a semiconductor substrate, and a dielectric layer over a backside surface of the semiconductor substrate. The dielectric layer has a sensing well extending through the dielectric layer to a channel region of the BioFET. The IC structure further includes a biosensing film, a plurality of fluid channel walls, and a first heater. The biosensing film lines the sensing well in the dielectric layer. The fluid channel walls are over the biosensing film and define a fluid containment region over the sensing well of the dielectric layer. The first heater is in the semiconductor substrate. The first heater has at least a portion overlapping with the fluid containment region.