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Labs and Research


SYSTEM DESIGN LABORATORY

The department has a long experience in Microprocessor/ PC based system design . Several application systems including Hardware and Software were developed as a part of the department`s research activities. Of late embedded systems with built in microcontrollers are being developed. Identifying specific applications, developing MIMICs of real systems, interfacing and software designs are the major activities carried out under this laboratory. Software for Metrology and Automatic trajectory tracking has been developed. Odor sensing based on Pattern recognition and Artificial Neural Networks is being investigated. The faculty of the department is also involved in Modeling and Simulation activities. Computer simulations are related to nonequilibrium phenomena, semiconductor devices and processes. The department has a longstanding program of VLSI design. The department has participated in a National Program of Technology Simulator Development sponsored by DOE. The laboratory focuses on applications of Digital Signal Processing and Image Processing in various fields. The DSP applications have been developed for speech recognition and synthesis. PC based Image Inspection systems using Reference comparison as well as Feature extraction approaches have also been realized. Software for metrology and Automatic trajectory tracking has been developed. Work on Tactile data processing and analysis is underway. Odor sensing based on Pattern recognition and Artificial Neural Networks is being investigated. This laboratory is another major part of the infrastructure wherein the student`s dexterity with regards to the microprocessors and computers is improved.


Electronic Nose

A PC based odor sensing system (PCBOSS) has been designed. A software package ODAP has been developed for acquisition and analysis of odors. The system has been successfully used for the identification of various gases, analyzing mixtures, detection of odors like perfumes, essences, ethers and alcohols. An analog circuit to implement the electronic nose has also been developed.


CYBER LAB FOR ELECTRONICS

Development of a laboratory in which students could carry out experiments over the web has been taken up as a UGC project. Presently basic experiments related to device characterization and digital electronics are being set up. With the advent of Internet and World Wide Web with horde of information the teaching methods need to be upgraded. The class room teaching needs to be supported with hands on laboratory exercises even in the commercial training systems. Many of the learning courses launched to date provide a good alternative/ complaint to classroom teaching with the support of web enabled multimedia lessons. However especially for courses like electronics just the multimedia presentation is not enough and feels of actually working on a real system observing the positive and negative results of various actions is must. In view of such a need for hands on, many a times online courses need to be added with a laboratory component.

In the past, students had to be in the laboratory to gain practical experience; with effective remote laboratories, students can be anywhere. Practical experience is a very important part of engineering education, but it is resource intensive. Designing and conducting experiments can take time, money and energy. Sharing experiments locally and remotely allows unique laboratory experiment to be utilized more fully, brings down the experiment cost per student, and more time available to students. Our goal with the remote laboratory paradigm is to make the equipment that we already have available to more students without taking away the experience of being physically present in the laboratory. Internet provides the communication infrastructure between students and the experiments.


The objectives of the project could be briefly stated as

Explore the range of WWW technology available for preparing the course material.
Experiment with the use of features offered by Netscape, CGI scripts and Java in imparting knowledge.
Prepare course material for the courses.
Use the material for various student groups and update it based on student's feedback.

The achievements during the course of past one year could be stated as Review of work on online courses and remote experimentation using web technology.

Study of Java, Java applets, Graphics and CGI scripts.
Implementations of Electronic Components like transistors, diodes, resistors, gates etc for CyberLab.


Automatic Trajectory Plotting System (ATPS):

A system for digitizing and analyzing a sequence of images and obtain the trajectory of a particular object has been developed. The software is menu driven and user interactive. The ATPS could be used for a number of applications. It has been used for tracking a moving vehicle and an insect.

FPGA based system design:

Work on implementation of Algorithms and systems in Field programmable gate arrays is being carried out. A digital frequency meter, printer interface, template search routine and image registration has been realized.

Tactile Sensing System:

A PC Based tactile sensing system has been designed. A menu driven software package providing various options for acquisition and analysis of data has been designed. The system has been used for identification of geometric objects.



SENSORS, MATERIALS and MEMS LABORATORIES:

The department possesses good research level facilities for fabrication of discrete semiconductor devices. Oxidation and Diffusion furnaces, vacuum evaporation and magnetron sputtering systems for metallization, ebeam evaporation system, photolithography setup, ebeam lithography system are the important facilities available in the department in fabrication laboratory ( FAB Lab ). The FAB Lab has a fully equipped yellow room for optical lithography purpose. A SEM and plasma processing set up are also available for material characterization/processing . Development of Silicon based and thin/thick film microsensors is another activity carried out in the laboratory. A system has been made by setting up for micromachining of silicon and it has shown encouraging results in the attempt to fabricate micropressure sensors. This laboratory is engaged in carrying out research on synthesis and characterization of Plasma Polymerized Electron Beam Resist.

Triple purpose EBL system using SEM model S120:

Lithography is a technique of transferring of pattern from mask to workpiece. Electron beam lithography (EBL) uses electronic beam as a source of exposure and is mainly used for the mask fabrication for optical and Xray lithography. Commercially available EBL machines are very expensive and are unaffordable to many.

A successful attempt has been made to develop an in-house EBL system (lc EBLS1), around a Scanning Electron Microscope, Type SEM120, Cambridge instruments. This is a triple purpose system. It can be used to evaluate the resist, to make mask and to inspect the mask or pattern delineated in the resist. A user friendly software is developed to have a fine control over the electron beam. The SEM is calibrated for the measurement of the electron beam dose. Fabrication of transducers like SAW devices, optical gratings, silicon based sensors, strain gauges etc. which requires fine control of line patterns of extremely small dimensions are carried out using this instrument.

Silicon Micromatching:

Polymers as Masking Material for silicon micromachining: i) PMMA, ii) PTFE, iii) HEMA

Polymers can be very good alternative to SiO2 and Si3N4 which are normally used masks for the anisotropic etching of silicon in etchants like KOH. PMMA has been extensively studied due to its use in numerous applications. Adherent PMMA layer can be conventionally used as a mask material as it is cheaper, easily deposited and removed. PMMA can be deposited by different techniques like plasma polymerization, thermal coating, DC and RF sputtering etc.

In the present work the deposition of PMMA is carried out using DC sputtering system at a pressure of 0.2 Torr in argon gas (carrier gas) plasma. The DC plasma power was varied from 540W and the deposition time from 2035min. The structural characteristics of the deposited films was carried out by NMR, FTIR and contact angle measurement. FTIR and NMR shows bond formation between silicon substrate and the deposited polymer film. From the contact angle measurement, the interfacial tension value obtained for sputtered PMMA layer is 0.8dyne/cm, which is in good agreement with the reported one. This indicates that the sputtered PMMA layer adheres well with the silicon substrate.

The masking properties of sputtered deposited PMMA was carried out by immersing the deposited films in aq. KOH solution of 20wt% concentration at 6080oC. The masking time of 300min at 80oC KOH temperature is achieved with the silicon etch rate of 86m/hr. These results show that, DC sputtering of PMMA gives better adhesion of polymer to the substrate and enhance the surface wetability and hence works well as a good masking material for silicon micromachining. Further on the same lines work on the test of masking properties of PTFE and HEMA is also done.


Design and Analysis of various MEMS structures using MEMCAD and ANSYS software:

Micro Electromechanical Mechanical Systems (MEMS) devices are generally geometrically complicated and innately 3dimensional. Appropriate Computer Aided Engineering (CAE) allow designer to model, simulate, modify and optimize the MEM device structure, process and design. FiniteElementAnalysis (FEA) is one of the numerical methods that is not restricted by size considerations of a structure and is always suited for the study of microminiature structure of MEMS devices. The modeling of inertial piezoresistive sensor a MEM device is done by using one of the CAE tools i.e. FEA tools, ANSYS. A sensor structure consisting of a pi shaped proof mask and piezoresistive doped flexure is modeled in variety of sizes. FEA is carried out for computing sensorsensitivity through measurement of strain in the flexure by statistically loading the proof mask.

After the extensive simulations of various types of structures, a novel technique has been evolved to maximize the performance of acceleration sensor. This technique involves placement of lumped mass on a proof mass at a particular position from anchored end, which results in optimized product of stress and bandwidth. The design optimization for piezoresistive inertial sensor in respect of maximization of sensitivity and bandwidth has been done.

Thin Film Studies

Deposition of Silicon nitride (Si3N4) and Indium nitride (InN) by ARE process

Activated Reactive Evaporation (ARE) process is implemented for the deposition of silicon nitride as well as indium nitride thin films at room temperature. In the Activated Reactive Evaporation (ARE) process, evaporated material by ebeam/ resistive heating enters in the nitrogen plasma zone, excited by inductively/parallel plate RF power (13.56MHz) source and the films get deposited on the substrate. Large number of experiments were carried out for optimization of the process parameters.

The deposited films of silicon and indium nitride are characterized by various characterization techniques like Elliposmetry for refractive index measurement, Xray Diffraction (XRD), Xray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR) spectroscopy, Energy Dispersive Analysis of Xray (EDAX) for chemical and structural analysis and topography by Scanning Electron Microscopy (SEM). The results obtained from these various analysis show the feasibility of using ARE technique for the deposition of silicon and indium nitride thin films.


Sensors

Polymer based Humidity sensor

In order to fabricate humidity sensors using polymeric materials, modification of the polymer material by chemical or some other means to meet the requirements for reliable humidity sensor is necessary. In case of capacitive type humidity sensor, hydrophobic polymers are used to fabricate the sensor. It is found that the polymer should have a few microvoids as possible so that the adsorbed water molecules are isolated in order not to form clusters. The formation of clusters leads to appreciable hysteresis. The aim of the present work is to synthesize a new polymer material, basically PMMA, for humidity sensing in which sensitivity could be improved. In this regard two methods are employed: In the first case the aim is to synthesize PMMA via plasma polymerization route using MMA as the base monomer in an inductively coupled plasma polymerization reactor and to study the RH response of the PPMMA films deposited under various conditions. In the second case the objective is to study the effect of argon and nitrogen plasma treatments on PMMA and consequently for the first time its effect on RH response of the polymer with respect to sensitivity, hysteresis and response time. The "Inter Digited Capacitor (IDC)" pattern is transferred on chromium coated glass substrate by photolithography. These samples were exposed to the plasma polymerization of MMA at a reactor pressure of 102 Torr in argon as well as nitrogen (carrier gas) plasma. After the plasma treatment the samples were exposed to different humidity and the sensor responses were recorded.

Silicon based Hall sensors for RPM measurement

Hall sensor is developed indigenously for use in Automobile industries for RPM measurements of the wheels. Single crystal Silicon (ntype, (100) orientation, and = 35 cm) is used as Hall sensor material. Ti - Pt - Au were used as the electrode material for Hall Sensors. These metals were deposited by E beam evaporation. The pattern was transferred by lift off technique. The sensors were separated out and tested thoroughly. These sensors are stable with respect to time as well as temperature (R.T to 55 ?C). They have linear Hall characteristics and the contacts are ohmic.

This has been proved mathematically by considering work functions of each and through the experiments as well. The Halldevices so fabricated are tested for Hall voltage, using the setup built in house. Si based Hall devices and RPM measurement system consisting of Signal Conditioning Unit (SCU), Optical Isolator for separating analog and digital ground, Counter and Power Supply is successfully fabricated. The same is handed over to VRDE, Ahmednagar, for its application in RPM measurement. These circuits were developed using discrete components initially. Now they are fabricated using SMDs (surface mount devices) as well.

Synthesis of Dry Electron Beam Resist by Plasma Polymerization

Work is done on synthesis and characterization of plasma polymerized electron beam resists. An inductively coupled tubular reactor is employed for plasma polymerization. Methyl Methacrylate (MMA), Styrene, aMethyl Styrene are the monomers for resist synthesis. Copolymerization and doping of resists by metals and gaseous species like Sulfur (S), Fluorine (F) is being done for improving the sensitivity of the resist.

Plasma Polymerization is a dry and clean process, which gives pinhole free resist whose characteristics can be tailored easily.

Plasma Polymerized MMA resist synthesized in the laboratory is found to be self developable and has very high sensitivity compared to the conventional ones. S and F doping further increases the sensitivity.

Microwave

Development of NOAA receiver

Data on various earth survey related parameters are available from geostationary (distance of about 36000km) and polar (e.g. NOAA at distance of 830km) satellites. There are few data collection centers in India especially in national laboratories only. A low cost receiver for National Ocean for Atmospheric and Administration (NOAA) satellite for collecting the atmospheric data has been designed and developed. A typical receiver consists of receiving Antenna (AE), Low Noise Amplifier (LNA), Filter, Mixer, IF amplifier and Down converter with PC for imaging. Power output requirements from various stages are calculated and the stages are designed. Parabolic reflector AE with helical feed to operate at 1.7GHz has been designed and fabricated. Azimuth and elevation control for tracking the satellite is done through PC. The components, active and passive, are selected to give the expected performance and cost.


OPTOELECTRONIC SENSORS AND SYSTEMS LABORATORY

Optoelectronics includes study of Light sources, transmission media and photodetectors. The research activities carried out in the Optoelectronic Sensors and Systems Laboratory include development of Integrated Optical components, MSM photodetectors, Universal Signal Conditioning system and fiber optic sensors for mechanical and chemical applications. Transmissive ESLMs using twisted pneumatic liquid crystal are designed and fabricated consisting of a 32 x 32 matrix pixel for optoelectronic logic processing. Presently, the activities are related to optical waveguides fabricated in glass using the ionexchange technique. Stress is laid on the sensing applications of integrated optic devices.

Embedded Optical Fiber Sensor Modules:

Developed and optimized fiber optic based micro displacement sensor. The sensor is also used for strain, and load measurements. The strain and load measurement range can be selected with different diaphragms. This is optical reflectance measurement type sensor probe.
Multi wavelength fiber optic based fluorescence sensor for chemical analysis like pH, concentration and RI measurements of liquid and fluids.
Fiber optic U shaped and Planer Optical Waveguide based online RI monitoring and measurement sensor for liquids and fluids in Sugar Industries, Food Processing and Chemical Industries to analyze the concentration of ingredients, turbidity and viscosity etc.
TriColorimetry based fiber optic probe for color sensing
MSM Photodetector
These sensors are accommodated with individual signal conditioning and processing modules based on discrete components, microcontrollers and PCs. Application areas include Process, Instrumentation manufacturers, Sugar, Chemical, Food Processing, Paper and Textile Industries.

Rapid Thermal Processing (RTP) System:

Developed in this laboratory is designed for semiconductor wafer processing at temperature in excess and of the order of 1000OC with a ramp up rate of 220 OC in a matter of about 5 to 6seconds. The SS process chamber is isolated form the heating lamps with quartz separators. A gas premixing assembly with MFCS allows mixing of up to 4 corrosive/noncorrosive gases. Thus making the system capable of working in variety of environments.

Provision is also made to attach rotary pumps for processing in vacuum. PC based recipe controller software provides overall monitoring and control. The dedicated PID controller maintains the wafer temperature within 5OC.

VIRTUAL INSTRUMENTATION LABORATORY:

A Virtual Instrumentation lab has been set up in collaboration with National Instruments, a Texas based company. Virtual Instruments for various applications are being developed.

The field of instrumentation has been revolutionized with the advent of computer age. Today the front panel as well as hardware of the instrument is being substituted with software, making the instrument cheaper, more versatile and virtual. The concept of virtual instrumentation has not only influenced the industry but is also affecting traditional academic research and teaching. It gives the ability to transform a personal computer into a number of powerful Virtual Instruments. The field of VI is breaking down the barriers developing and maintaining instruments that challenge the world of test, measurement and industrial automation.

Today globally competitive economy requires scientists, engineers and technicians who are competent with products used in the industry. The Department of Electronic Science has acquired expertise in the field of Microprocessor/PC based Instrument over the past 20 years. The research activity is focused on Intelligent Instrumentation along with DSP, Image processing, Machine Vision, Neural Network and Fuzzy Systems. Considering the expertise available in the Department, National Instruments, a Texas based company has come forward to collaborate and setup a Virtual Instrumentation laboratory on the Pune University Campus.

Hundreds of universities, technical schools abroad have made transition to virtual instrumentation. The emergence of computers as a multipurpose engineering and scientific tool can make researchers, teachers more productive and change the way students learn. The computers can be transformed into powerful, multipurpose laboratory tools that can replace expensive, outdated equipment.

The department has been actively pursuing the research in basic and applied sciences along with various developmental projects. This part of the research has been an integrated part with a view to understand and contribute to the future technology to come. Following is a brief summery of the research done. Dr. Shaligram has participated in the MOSTEC programme initiated at all India level to develop a software package for MOS processing. This was an attempt to analyze various processes as surface chemical processes and connecting the outcome to the experimental macroscopic parameters. The software was published in 1990.

Simulation:

Software is developed for IV characteristics for a MOS transistor. The program involved calculations of 2D states of triangular potential well for silicon at the oxide interface. The calculation of current involved the Monte Carlo method to sample the electrons representing the current. Various scattering processes were included within effective mass approximation including ee scattering. This lead to very satisfactory results with experimental curves.

In association with Univ. South. Cal. USA a code for atomistic growth of GaAs and AlGaAs using known diffusion coefficient and relevant properties of corresponding elements in the vapor form has been developed. This work has successfully explained various observations on IIIV compound growth including RHEED oscillations, temperature dependence of layer by layer growth, roughening of interfaces between GaAs and AlGaAs, etc. The work is still cited in many publications.

In another collaboration with University of Maryland USA, simulations on various models are carried out to understand the statistical physics of growth. This included conservative as well as non conservative growths.

Collaborative work with U. Mich. Ann Arbor, USA is being carried out to understand the catalytic behavior of CO on Pt surfaces. The main interest was to understand the oscillatory behavior of surface reaction. This turns out to be a problem in non linear dynamics. Using methods in NLD, we have successfully obtained the simulation results on oscillatory reactions.

Further, we also studied the problem of brittle cracks in SiO2. The well known fact that the micro cracks are developed well before the critical stress is applied was explained using the effect of viscosity and thermal noise. The simulation results with parameters for SiO2 match well with corresponding experimental data.

Recently work is being carried out on establishing electronic structures of quantum dots of CdSe and ZnSe along with other collaborators in Physics Dept. of the Pune University. This study is intended to explain some of the experimental observations in spectroscopy related to quantum dots and also the diffusion behavior of nano particles.


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