טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMorgenshtein Arkadiy
SubjectDesign and Methodology of ISFET (Ion Sensitive Field
Effect Transistor) Microsystems for Biotelemetry
DepartmentDepartment of Biomedical Engineering
Supervisors Professor Emeritus Uri Dinnar (Deceased)
Professor Emeritus Yael Nemirovsky


Abstract

The monolithic implementation of biomedical sensors on-chip together with signal processing electronics for improved diagnostics and therapy is an important research issue. Several fabrication processes of ISFET devices in standard CMOS technology were recently presented, offering a basis for future development of miniature implantable device for “in vivo” monitoring of pH changes in biological fluids. Miniaturization allows compatibility for clinical catheter applications and bio‑telemetry. Integration of various interfaces and sensors on-chip makes the design suitable for implantable sensor systems.

This Thesis describes the research and development of novel readout interfaces and microsystem architectures that allow the integration of the ISFET in system-on-chip structures in biotelemetry, basing on standard CMOS technology.

Novel readout techniques of Complementary ISFET-MOSFET Pair and Wheatstone Bridge were developed and presented in this Research with theoretical analysis, simulations and verification by laboratory tests. The novel techniques allow simple and efficient implementation with advanced features as temperature compensation, body effect elimination, controlled sensitivity, as well as operation in REFET mode.

An original concept of ISFET sensor operation without readout interface, basing on threshold drop in Pass Transistor mode, was developed, simulated and measured in test-chip and commercial ISFETs. A Combined ISFET-APS sensor was developed to obtain simultaneous pH and image monitoring via a single sensor. The simulations of the structure are presented, followed by a discussion of future biomedical applicability and fabrication considerations of the sensor.

New method of Floating Point Analog-to-Digital conversion with BCD output for wireless data transmission in biotelemetry is also discussed. Finally, the novel architecture of complete pH measurement microsystem is presented with implemented prototype.

The technology considerations and applicability in biotelemetry and other clinical fields are presented for all the designed systems. The proposed interfaces and architectures have been submitted and published in journal and conference papers.