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A CMOS-Compatible, Low-Noise ISFET Based on High Efficiency Ion-Modulated Lateral-Bipolar Conduction
Institute of Electronics Engineering, National Tsing Hua University, 30013 HsinChu, Taiwan
* Author to whom correspondence should be addressed.
Received: 30 July 2009; in revised form: 25 September 2009 / Accepted: 14 October 2009 / Published: 21 October 2009
Abstract: Ion-sensitive, field-effect transistors (ISFET) have been useful biosensors in many applications. However, the signal-to-noise ratio of the ISFET is limited by its intrinsic, low-frequency noise. This paper presents an ISFET capable of utilizing lateral-bipolar conduction to reduce low-frequency noise. With a particular layout design, the conduction efficiency is further enhanced. Moreover, the ISFET is compatible with the standard CMOS technology. All materials above the gate-oxide are removed by simple, die-level post-CMOS process, allowing ions to modulate the lateral-bipolar current directly. By varying the gate-to-bulk voltage, the operation mode of the ISFET is controlled effectively, so is the noise performance measured and compared. Finally, the biasing conditions preferable for different low-noise applications are identified. Under the identified biasing condition, the signal-to-noise ratio of the ISFET as a pH sensor is proved to be improved by more than five times.
Keywords: ISFET; low noise; CMOS-compatible; lateral-bipolar conduction
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MDPI and ACS Style
Chang, S.-R.; Chen, H. A CMOS-Compatible, Low-Noise ISFET Based on High Efficiency Ion-Modulated Lateral-Bipolar Conduction. Sensors 2009, 9, 8336-8348.
Chang S-R, Chen H. A CMOS-Compatible, Low-Noise ISFET Based on High Efficiency Ion-Modulated Lateral-Bipolar Conduction. Sensors. 2009; 9(10):8336-8348.
Chang, Sheng-Ren; Chen, Hsin. 2009. "A CMOS-Compatible, Low-Noise ISFET Based on High Efficiency Ion-Modulated Lateral-Bipolar Conduction." Sensors 9, no. 10: 8336-8348.