Rekabentuk dan fabrikasi isfet berasaskan silikon sebagai penderia pH
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Date
2007
Authors
Rozina, Abdul Rani
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Abstract
This thesis describes the research activities on pH sensor development by using Ion
Sensitive Field Effect Transistor (ISFET) approach. ISFET promises high potential in
medical and agriculture applications. Besides available in micro size and low cost of
sensor production, ISFET based silicon can be fabricated together with the electronic
circuitry and Biochemical-Micro-Electro-Mechanical System (BioMEMS) as an
integrated system.
ISFET-sensorCA and ISFET-sensorIB were fabricated by using standard
CMOS 1 μm process technology. Silicon Nitride, Si3N4 was used as an ion sensitive
layer and it was deposited by using chemical vapor deposition technique. ISFET
detects the hydrogen ion concentration which is indicating the pH level of electrolyte.
The ion changing between electrolyte and ion sensitive layer modify the channel
charge of ISFET. This situation creates a gate potential and then modulates the current
flow through the ISFET channel and gives a certain output voltage during the
measurement of readout circuitry output pins. The output voltage of readout circuitry is
converted to digital values by using PIC16F877A microcontroller and the value is
displayed on LCD. For ISFET analysis, two types of Ag/AgCl reference electrode; solid
and double junction reference electrode, and three types of pH buffer solutions; pH4,
pH7 and pH10 were used during the experiment. The reason of using different types of
reference electrode is to study the ability of each reference electrode in order to
establish a stable electrochemical potential. This stable condition will affect the ISFET
performance. During testing, the highest ISFET sensitivity which is 58.17 mV/pH was
obtained by using HF treatment. This research also evolves assistance of additional
software including L-Edit, MEMS Pro, T-Spice, S-Edit, Micro Basic and MASView.
Description
Master
Keywords
Industrial technology , Sensor application