Mohd Ismahadi Syono

Effects of Mechanical Geometries on Resonance Sensitivity of MEMS Out-of-Plane Accelerometer

Mechanical geometry such as flexures beam width, beam length, shin length and movable plates size variations have effects on the resonance frequency because its change the values of springs constant and mass of the structure. This paper presents the effects of these mechanical geometries on resonance of MEMS out-of-plane accelerometer using Architect module in CoventorWare. Resonance frequency of the accelerometer is important because it determines the working frequency bandwidth of the accelerometers. Sensitivity analysis is carried out to determine which geometry most affects the device performance and needs to be controlled. An out-of-plane accelerometer with a fixed and a movable plate suspended by four flexures is used. Sensitivity by analysis shows resonant frequency decreases by 1.422% with 1% increase in beam length while the lowest changes is -0.061% of resonant frequency with 1 % increase in shin length.

Sputtered titanium dioxide thin film for Extended-Gate FET sensor application

This paper presents an investigation on sputtered titanium dioxide (TiO2) thin film for application in the Extended-Gate Field Effect Transistor (EGFET) sensor application for pH detection. The TiO2 thin film was fabricated on conductive indium-tin oxide (ITO) covered glass by using RF Sputtering method. An EGFET proof-of-concept setup was constructed using a commercial FET as the transducer and the TiO2/ITO structure was used for the extended gate. The sensor measurement was taken using semiconductor device parametric analyzer, constant-current constant-voltage biasing interfacing circuit and data logger to obtain the sensitivity and the characteristics for output voltage with respect to time. TiO2 thin film on ITO glass as the sensing membrane was compared with a bare ITO glass substrate for the extended gate. The TiO2/ITO glass exhibited the sensitivity of 42.1 mV/pH and good linearity of 0.9997 in the sensing range pH4, pH7 and pH10 which was better than the bare ITO glass sensitivity of 31.3 mV/pH and the linearity of 0.9868.

TCAD process simulation for light effect improvement of ion sensitive field effect transistor

The conventional open gate ISFET sensor is normally very sensitive to light exposure which influences the sensor characteristics. In this study, different process conditions of ISFET were simulated using SILVACO TCAD in order to find the right doping profile which minimizes light effect. Various channels doping levels for ISFET sensor have been analyzed. Comparison with SRP samples was done in order to ensure the accuracy of the simulation output. Based on simulation results, the ISFETs were then fabricated and tested under the same intensities of light exposure and ambient temperatures. It shows that ISFET which underwent double PWELL implant and with deeper junction depth experiences lower light effect. This paper will discuss on how doping profiles affect ISFET performance with respect to light effect.

Multi-finger gate ISFET (Mf-ISFET) for pH sensor application.

Study on Ion Sensitive Field Effect Transistor (ISFET) based on multi-finger gate design is presented. Mf-ISFET was fabricated by using commercial submicron 1.0 mum CMOS technology and deposited with PECVD Si3N4 as a sensing membrane. The electrical data such as IdVd and IdVg of ISFET are measured to identify the behaviours of ISFET. Furthermore, the evaluation test on ISFET performance such as transient analysis and hysteresis is also done and discussed in this paper. Based on experimental result gained, better performance of ISFET can be archived by ldquoconditioningrdquo the ISFET before applying it as a sensor.

Development of a CMOS-compatible electrostatically actuated diaphragm chamber for micropump application

This paper presents the development of a diaphragm chamber actuated electrostatically utilizing CMOS-compatible silicon micromachining fabrication process. The process consists of six photolithography steps and five chemical vapor depositions. Etching of the sacrificial oxide layer for the diaphragm chamber is achieved using etch-release holes perforated on the diaphragm, similar to via holes used in IC-fabrication method. From the analysis, the best encapsulation has been successfully demonstrated by growing LPCVD silicon nitride of thickness 0.9¿m. Accomplishing this feat enables electrostatically actuated diaphragm chamber to be developed and in particular, will spur advancement in the development of a CMOS-compatible electrostatically actuated diaphragm micropump.

A coupled-field fluid-structure interaction (FSI) simulation of an electrostatically actuated diaphragm valveless micropump (EDVM)

In this study, a novel approach in designing an electrostatically actuated diaphragm valveless micropump (EDVM) based on CMOS-compatible surface micromachining (SMM) fabrication process has been presented. One major advantage of the designed EDVM using SMM process as compared to conventional EDVM fabricated using bulk micromachining process is that the actuation voltage is now applied across the working fluid. The working fluid must be included in the simulations as it will now have a major influence on the response and characteristics of the micropump. In view of that, a coupled-field electro-mechanical-fluidic model of the EDVM has been simulated using MemFSItrade, a fluid-structure interaction (FSI) solver available in CoventorWaretrade software package. Results obtained from the CoventorWaretrade simulations are compared with analytical studies for verification purposes. The designed EDVM with a diaphragm size of 1mm times 1mm times 0.5 mum is able to generate flow rates of up to 10nl/min for a low actuation voltage of 3V.

Electrochemical Measurements of Multiwalled Carbon Nanotubes under Different Plasma Treatments

In the present work, we described the post-treatment effects of applying different plasma atmosphere conditions on the electrochemical performances of the multiwalled carbon nanotubes (MWCNTs). For the study, a composite of MWCNTs/Co/Ti was successfully grown on the silicon substrate and then pre-treated with ammonia, oxygen and hydrogen plasma. The composite was characterized by making use of field emission scanning electron microscopy (FESEM) for the surface morphology and Raman spectroscopy for the functionalization. Further, the electrochemical measurements were performed with the use of the cyclic voltammetry (CV) applied in the 0.01 M potassium ferricyanide in 0.1 M KCl solution. On testing, the results indicated that the NH3-treated MWCNTs have the highest efficiency as compared to the other pretreatments and control. This increased performance of NH3 treated sample can be linked to the enhanced surface area of the composite, thereby improved adsorption and associated interaction with that of the analyte molecules at the electrodes. Further comparison of the electrode with that of commercial Dropsens electrodes provided the confirmation for the efficiency of the NH3/MWCNTs, thereby suggesting for the potentiality of applying the NH3 modified electrode towards electrochemical applications.

Operational of ISFET as a pH Sensor by Using Signal Modulated Reference Electrode

As an alternative to miniaturize sensor size, study on Ion Sensitive Field Effect Transistor (ISFET) as a pH sensor by applying AC modulation signal to the reference electrode is presented. The small size of solid state reference electrode was fabricated onto the silicon. The reference electrode was developed by using metal and covered with an insulator. An AC modulating signal, from 10 Hz up to 1 MHz is used to study the biasing effect to the reference electrode and subsequently to modulate ISFET channel for output. From the experimental result, ISFET was successfully responding as a pH sensor at low frequency of AC modulating signal.

A novel CMOS-compatible fabrication method for development of an electrostatically actuated micropump

This paper presents the development of a novel micropump actuated electrostatically utilizing CMOS-compatible silicon micromachining fabrication process. The fabrication process consists of six photolithography steps and five chemical vapor depositions. Etching of the sacrificial oxide layer for the diaphragm chamber, microchannels and inlet/outlet reservoirs are achieved using etch-release holes perforated on the polysilicon layer, similar to via holes used in IC-fabrication method. The sacrificial oxide etching and encapsulation of the etch-release holes have been successfully accomplished by using BOE etchants for 17 minutes and by growing LPCVD silicon nitride of thickness 0.9 μm respectively. Accomplishing this feat enables CMOS-compatible electrostatically actuated micropump to be developed with potential integration with CMOS-based sensors, readout circuits and packaging, on a single wafer.

Characterizations of single gate and multi-finger gate of ISFET for pH sensor applications

This paper discuss the characterization and the performance of two types of ISFET, which have different gate design. Isfet5 has single gate while Isfet7 has multi-finger gate. The characterization of ISFET is analyzed from the IdVd and IdVg curve, and by measuring the threshold voltage, Vth and response-time of ISFET in order to determine the sensitivity of ISFET. Beside, the hysteresis of ISFET is also measured during the experiment. The Vth value extracted from IdVg curve shows that Isfet7 has higher sensitivity compared to Isfet5. While from the response-time, Isfet5 has better sensitivity than Isfet7. In term of hysteresis effect, Isfet7 has less effect of hysteresis compared to Isfet5. However, from the correlation between sensitivity and pH value graph, based on Vth value and response-time, both graphs conclude that Isfet5 has more linear profile with regression value, R2 more than 0.9960.