M.Sc Thesis

M.Sc StudentSudakov Liby
SubjectDesign and Methodologies of CMOS Compatible ISFFT (Ion
Sensitive Field Effect Transistor) for Brain
Monitoring in Head Injury Patients
DepartmentDepartment of Biomedical Engineering
Supervisors PROFESSOR EMERITUS Yael Nemirovsky
PROFESSOR EMERITUS Uri Dinnar (Deceased)


Traumatic Brain Injury (TBI) is a sudden physical damage to the brain usually caused by mechanical impact to the head. Therapeutic treatment of TBI injures can be improved significantly by continuous local monitoring, which will assist medical team to recognize damages and supply a rapid and an accurate treatment. A sensing system for local brain monitoring has to have low cost, to be robust and biocompatible and to be able to supply long period measurements with stable results.

During the last 9 years of intensive research local brain monitoring micro system based CMOS compatible ISFET - Ion Sensitive Field Effect Transistor was developed. ISFET is a potentiometric pH sensor that is easily adapted to wide range of chemical, biochemical and biomedical measurements. ISFETs based on standard CMOS technology can serve as building blocks of new micro systems incorporating ISFETs, CMOS electronics, as well as other CMOS compatible sensors and actuators.

This research was focused on fabrication issues of CMOS compatible ISFETs such as encapsulation and reference electrode. In addition, we research studied and successfully implemented the new read-out technique proposed by Arkadiy Morgenshtein for CMOS compatible ISFETs.

The novel encapsulation techniques are:

  • “Planar and Flip Chip Bonding” chip-like encapsulation techniques;

  • “Planar and Flip Chip Bonding” catheter encapsulation technique.

All the methods mentioned above also include implementation of a novel pseudo reference electrode. The techniques are performed on ISFET which is implemented in standard CMOS process. Chip-like encapsulation techniques use pieces of preprocessed silicon wafer as a package, when catheters encapsulation employs ceramic alumina as a harsh basis for ISFETs and wiring system.  Samples were developed, measured and studied.

This research also dealt with read-out problem.

Since ISFET output is expressed by variations of device physical parameters, some read out blocks which translate ISFETs parameters changes into electrical voltage or current fluctuations are required. In this research we prove a new “read-out” - Pass Transistors Mode. This technique saves chip area, power consumption, and thus cost. The method was tested and measured on sensors fabricated in standard CMOS process.