Murat Baylav


This study involves the design and fabrication of an Ion-Sensitive Field Effect Transistor (ISFET), which is aimed to be incorporated into the multisensory chips fabricated at RIT. ISFETs are used for various purposes in biomedical, medicine, and chemical applications and have advantages such as small size, low power consumption, robustness, and fast response time, over the ion-selective electrode (ISE) counterparts. The capability of fabricating ISFETs in a standard CMOS process let them to be used in sensor systems together with the dedicated signal processing circuitry which in turn makes portable applications possible. The ISFET fabricated in this study have a SiO2 gate oxide and on top of that a Si3N4 layer. The latter layer, in addition to passivating the device, serves as a pH sensitive membrane. The overall process has 5 mask levels and the electrical tests, which were performed using buffer solutions with varying pH values, indicated that the transistor can be employed to measure the pH of solutions. ISFETs were also tested against environmental conditions such as temperature, long term exposure to various pH-valued solutions and it is found out that the FETs are quite robust in terms of temperature stability and long term drift. In addition to their pH sensing properties, these devices were also taken one step ahead to sense chloride ion (Cl-) concentration via preparing a Cl--sensitive membrane stacked on top of the Si3N4 layer. Electrical tests, which were performed in solutions with various Cl- concentrations, showed that the modified ISFETs are also Cl- sensitive.

Library of Congress Subject Headings

Metal oxide semiconductor field-effect transistors--Design and construction; Electrodes, Ion selective

Publication Date


Document Type


Department, Program, or Center

Microelectronic Engineering (KGCOE)


Fuller, Lynn


Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works. Physical copy available through RIT's The Wallace Library at: TK7871.99.M44 B39 2010


RIT – Main Campus