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

Volume

35

Issue

12

fYear

2014

fDate

Dec. 2014

Firstpage

1302

Lastpage

1304

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;

fLanguage

English

Journal_Title

Electron Device Letters, IEEE

Publisher

ieee

ISSN

0741-3106

Type

jour

DOI

10.1109/LED.2014.2365478

Filename

6954697