PROJECTS

Piezoresistive Pressure Sensor Development for Industry

Position: Fabrication and Packaging.
Date: January 2001 - .

This project aims to produce low-cost piezoresistive pressure sensors with various sensitivities for industrial applications. This variation in the sensitivity of the sensor will enlarge the application areas of the sensors. Sensor cluster will also include temperature sensors. The Temperature information can be obtained and can be used for temperature compensation purposes. In this project I am responsible from the sensor fabrication process flow optimization, sensor fabrication, and packaging of the sensor cluster.
Project Web Site


An Uncooled Infrared CMOS Imager Chip Design

Position: Sensor Design and Post CMOS Fabrication.
Date: October 1998 - .

This project aims the development of a microbolometer type uncooled CMOS infrared imager, including a pixel array and on-chip readout circuit. In this project I am responsible from the development and optimization of sensor pixel design for a standard CMOS process, layout implementation, and post-processing of the fabricated chips. A new micromolometer structure composed of suspended n-well resistor with polysilicon and silicon dioxide support arms has been developed. Various pixels have been designed in different dimension and in different sensing structures for characterization. Layout implementation of the design was performed in CADENCE design environment using AMS 0.8 µm CMOS process. The design was verified for post-CMOS silicon anisotropic etching process using Intellisense Anise. After CMOS fabrication of the design, electrochemical etching of bulk silicon was performed in TMAH solution to release suspended n-well resistors. Initial tests have been done on the sensor pixels and the sensor parameters have been measured. This work was presented in the TRANSDUCERS'99 Conference in Sendai, Japan. In addition, a 16´16 focal plane array chip with readout circuit has been designed in our group and fabricated using AMS process. Post-process etching of the array was performed successfully. The initial tests on the chips have shown that the designed circuits operate successfully. Currently, both the imager pixels and the readout circuit are under continuous development for improved sensitive and superior readout performance in our group.
Project Web Site


Integrated Thermopile Structure with High Responsivity and Detectivity in Standard CMOS Technology

Position: Sensor Design, Post CMOS Fabrication.
Date: October 1996 - September 1997.

In this project, main objective was to develop a thermopile type single IR detector in any standard CMOS process. New thermopile structure, which consists of thermocouples made of n-polysilicon/p+ diffusion, was introduced first time with this project. A number of thermopile pixels have been designed and fabricated using HP 1.2µm CMOS process, and the chips were post-processed for complete sensor structure. I was responsible from the design of the thermopile pixels, layout implementation of the design in MENTOR GRAPHICS environment, and post-processing of CMOS chips fabricated by MOSIS. Four probe electrochemical etching setup has been prepared for this project, and suspended n-well supports of the sensor pixels have been post-processed successfully using TMAH solution. This work was presented in the TRANSDUCERS'97 Conference in Chicago, USA, and in National Electric-Electronic-Computer Engineering Conference 1997 in Ankara, Turkey, and published in Sensors and Actuators Physical A, one of the prestigious journal in this field.
Project Web Site


M.S. Project : Silicon Micromachined Capacitive Pressure Sensor for Industrial and Biomedical Applications

Position: Sensor Design, Fabrication and Test
Date: January 1996 - Present

The scope of this project is the development of solid-state micromachined pressure sensor for process control and biomedical applications and the main objective is to introduce MEMS technology to the Turkish Industry. In this project I am responsible from the design, fabrication and testing of the micromachined capacitive pressure sensors. 12 capacitive pressure sensors have been designed and batch fabricated for 6 different pressure range. The design of the sensors have been completed in METU, and fabricated in Solid-State Electronics Laboratory at University of Michigan. The bulk micromachining technology and the boron etch-stop dissolved wafer process have been successfully utilized in the device fabrication. The sensors have been designed for industrial and biomedical applications. Both type of pressure sensors consist of pressure sensitive, parallel plate capacitor based on deflecting diaphragm. The industrial type pressure sensors have been connected to a switched capacitor (SC) readout circuit chip developed by the METU-MEMS-VLSI Group. In the laboratory tests, it has been verified that the designed circuit tracks the changes in the sensor capacitance with the applied pressure. The biomedical type pressure sensors are fabricated with electroplated planar rectangular coil inside of the sensor. This new sensor structure can be implanted in the body and blood pressure can be monitored telemetrically without using any wire. This research is the first national study on the design and implementation of silicon micromachined capacitive pressure sensors. It is also a part of the project shortly entitled as TU-MICROSYSTEMS sponsored by NATO Scientific Affairs Division in the framework of the Science for Stability (SfS) Program. Also it is supported by the National Science Foundation International Grant. This work was presented in National Electric-Electronic-Computer Engineering Conference 1997 in Ankara, Turkey, and wireless pressure sensor part of this project was presented in EUROSENSORS 2000 Conference in Denmark.
Project Web Site


Establishment of the Chemical Processing Laboratory and Cleanroom

Position: Equipment and chemical searching, purchasing, directing and active work on laboratory construction.
Date: January 1997 - Present

As an extension of TU-MICROSYSTEMS project, this work aims to create an infrastructure to implement various microsensors and microsystems at Electrical and Electronics Engineering Department at METU. I am responsible from directing and active work on laboratory construction, equipment and chemical searching, purchasing, and training of people in the laboratory. As a part of this work, a wet bench (hood) for chemical processing has been designed and been built for cleanroom. The construction of both laboratories has been completed. Currently, the laboratories are under continuous development.


B.S. Project: Etch-Stop Techniques on Silicon Micromachining

Position: Research of etch-stop techniques, test wafer implementation, anisotropic silicon etching.
Date: January 1993 - June 1994.

This project was aiming investigation of etching mechanisms of moderately doped and highly boron doped silicon wafers in KOH solution as a base study for the implementation of microelectomechanical structures at Istanbul Technical Üniversity (ITÜ) Microelectronic Laboratory. Silicon micromachining techniques and etch-stop methods have been studied and etch-stop effect of high boron diffusion has been experimentally investigated in this project. A test mask was designed in L-Edit and prepared at Semiconductor Technology Research Laboratory (YITAL) at TÜBITAK Marmara Research Center (MAM). In addition, the highly boron doped silicon wafers were also prepared at YITAL. Wet silicon etching setup was prepared at ITÜ Microelectronic Laboratory. By using this setup, highly boron doped silicon wafers were etched in KOH solution and the etch-stop effect of boron diffusion was investigated. In addition, moderately doped silicon wafers were etched in 10 different temperature and 6 different concentration of KOH solution to investigate the etch-rate variation of the solution.