Title :
Effect of Sensing Film Thickness on Sensing Characteristics of Dual-Gate Poly-Si Ion-Sensitive Field-Effect-Transistors
Author :
Li-Chen Yen ; Ming-Tsyr Tang ; Chia-Ying Tan ; Tung-Ming Pan ; Tien-Sheng Chao
Author_Institution :
Dept. of Electrophys., Nat. Chiao Tung Univ., Hsinchu, Taiwan
Abstract :
We investigate the effect of sensing film thickness on the sensing characteristics of dual-gate (DG) poly-Si ion-sensitive field-effect transistors (ISFETs). The pH sensitivity (from 37.57 to 9.32 mV/pH) of the DG poly-Si ISFET device degrades with the increase in the sensing film thickness (from 20 to 120 nm), whereas hysteresis voltage (from 6.7 to 1.12 mV for a neutral to acid to alkaline to neural loop) and drift rate (from 13.47 to <;3 mV/h at pH 7) improve accordingly. An improved hysteresis and drift phenomena are attributed to the reduction in top-gate capacitance of the sensing membrane, causing a smaller capacitive-coupling ratio (top-gate capacitance of sensing membrane to bottom-gate capacitance of tetraethylorthosilicate oxide).
Keywords :
capacitance; chemical sensors; hysteresis; ion sensitive field effect transistors; silicon; Si; bottom gate capacitance; drift phenomena; dual gate polysilicon ISFET; hysteresis phenomena; ion sensitive field effect transistors; sensing characteristics; sensing film thickness; sensing membrane; size 20 nm to 120 nm; tetraethylorthosilicate oxide; top gate capacitance reduction; Capacitance; Field effect transistors; Films; Hysteresis; Sensitivity; Sensors; Drift; dual-gate (DG); hysteresis; ion-sensitive field-effect transistor (ISFET); poly-Si; sensitivity;
Journal_Title :
Electron Device Letters, IEEE
DOI :
10.1109/LED.2014.2365478
