Temperature and optical characteristics of tin oxide membrane gate ISFET

The influence of temperature and optical effects on ISFET performance are important. In this study, the temperature characteristics of the SnO/sub 2//Si/sub 3/N/sub 4//SiO/sub 2//Si ISFET are investigated by the zero temperature coefficient (T.C.) adjustment and the dual FET's configuration, respectively. The result show that a zero T.C. of the SnO/sub 2/ gate ISFET can be achieved when the appropriate operation current was set. Subsequently, the T.C. of tin oxide membrane/electrolyte interface can be evaluated by the dual FETs configuration. On the other hand, due to the SnO/sub 2/ gate ISFET is sensitive to the light exposure, thus in order to improve this drawback, a multi-structure ISFETs: SnO/sub 2//Al/SiO/sub 2//Si/sub 3/N/sub 4//Si ISFETs have been developed. In this structure, aluminum is used as a light shield, and the tin oxide is used as a pH sensitive layer. The results show the ISFETs with aluminum as a light shield have low light sensitivity compared with ISFETs without aluminum as a light shield.