Highly sensitive ion sensors using charge transfer technique

Accumulation method ion sensor (AMIS), an expected high sensitive ion sensor, is proposed and prototype one is fabricated using a charge coupled device (CCD) process. The principle of the accumulation method ion sensor is based on the charge transfer techniques. The AMIS is operated in a signal integration mode. Charges corresponded to an ion concentration is transferred from a sensing part to the floating diffusion region on several times, and the signal charges are accumulated in the floating diffusion region. It is expected that the signal-to-noise ratio (SNR) of the chemical potential information increases n0.5 times, as the signal is integrated n times. The output signal was measured by using the equivalent signal. It was found that the output signal from AMPS, which was integrated five times, was lineally changed to the input signal and the total sensitivity was 450 mV/pH. This sensitivity is about nine times higher than that of ion sensitive field-effect transistor (ISFET).