Soumendu Sinha

Title : Development of Sensing Film Materials using Reactive Sputtering Process for FET based pH Sensors

Abstract:

Ion-Sensitive Field-Effect-Transistor (ISFET)-based chemical/biochemical sensors are used for measuring ion concentrations analyte solutions. Most commonly, they are used as pH sensors, where the current through the transistor changes with respect to the ion concentration at the sensing region (gate). ISFET is a solid-state device, which makes it rugged for the measurement of ion activities in analytes, with the aid of a reference electrode and it has been widely used for pH measurements. pH is one of the most important parameters in agricultural, environmental, bio-medical and potable water studies. ISFET has attracted much interest due to the feasibility of facile integration with readout circuits. It is an alternative to the conventional glass membrane electrode-based pH sensors, where it enables measurements in ultra-small volumes with fast response. This work deals with the design, fabrication and characterization of ISFET-based pH sensors.

The most critical element in ISFET-based pH sensors is the sensing film deposited over the gate region of the sensor.  In this work, the sensing films are deposited using pulsed-DC magnetron-assisted reactive sputtering technique. Various process parameters for deposition of the film were optimized through several experiments. The deposition process for three sensing films were optimized, namely, AlN, Al₂O₃ and TiN, and their material characterization was carried out using various techniques. ISFET-based pH sensors were fabricated using well established, CMOS compatible unit processes. In this work, three variants of ISFET-based pH sensors have been fabricated with AlN, Al₂O₃ and TiN as the sensing films, using self-aligned process. The devices were encapsulated using the Dam-and-Fill technique and packaged using thick-film alumina technology. The sensors were characterized for pH sensing applications. Moreover, drift and hysteresis studies were performed for each sensor and low drift and hysteresis values were obtained for the fabricated ISFETs.

What will audience learn from your presentation?

• The audience will get an overview of FET-based pH sensors which has applications in various areas including environmental field studies, agricultural monitoring, biomedical monitoring, etc.
• The audience will also get an overview of the development of sensing films using sputtering technique, which is a cost-effective and simple physical vapor deposition process and they can utilize the technique for depositing several other types of dielectrics for various applications.
• The device fabrication process will be discussed and the characterization results will be presented, which will introduce the audience to a facile self-aligned CMOS-compatible device fabrication technique
• The talk will help the audience in understanding the development process of FET-based sensors which will be useful for the researchers working in the area of electrochemical chemical/biochemical sensors

Biography:

Dr. Soumendu Sinha received his B.E. (Hons.) in Electrical and Electronics Engineering from Birla Institute of Technology and Science (BITS), Pilani, and his M.Tech. and Ph.D. from Academy of Scientific and Innovative Research (AcSIR), India. He is currently working as a Senior Scientist in Semiconductor Devices Design Group at CSIR-CEERI, Pilani. He is also an Assistant Professor at AcSIR, India. He has authored and co-authored over 30 papers in reputed journals and national/international conferences. His current research interests are in the interdisciplinary areas of solid-state electrochemical sensors and MEMS-based sensors and transducers.