Utilizing an optical cavity to increase the saturation level in a Schottky-barrier IR image sensor

摘要

A precise evaluation of the photodiode storage capacitance in a platinum silicide Schottky-barrier IR image sensor with an optical cavity and in which an aluminum reflector is electrically grounded has revealed that the cavity capacitance between the aluminum reflector and the platinum silicide film, which is one of four components in the photodiode storage capacitance, is dominant. While this area of the photodiode has previously been investigated for its optical characteristics, the present study represents the first reported investigation on its electrical characteristics. In order to increase the saturation level of an image sensor, it is essential to increase the storage capacitance in its photodiode. The storage capacitance in the photodiode was shown to be increased not only by newly using but also by increasing the cavity capacitance. When the SiO$-2$/ film between the aluminum reflector and the platinum silicide film was replaced with SiN, total storage capacitance in the photodiode was successfully increased by a factor of 1.6, while the optical characteristics of the photodiode remained the same.