SELF-PACKAGED FLEXIBLE ELECTRONICS

Zeynep Celik-Butler

Electrical Engineering Department and NanoFAB Center

University of Texas at Arlington, Arlington, TX 76019

zbutler@uta.edu

Novel emerging sensor technologies and applications require low-cost, adaptable, and scalable, wafer and device level packaging. We present several designs for device-level self-packaged uncooled infrared (IR) microbolometers. Both rigid Si substrates and flexible polyimide substrates are discussed. Device level vacuum packaging is necessary for optimum microbolometer performance without sacrificing flexibility.

Two layers of sacrificial polyimide were utilized to package sensors in a vacuum cavity. Self-packaged uncooled microbolometer arrays of 40x40 μm² and 60x60 μm² were fabricated on a Si wafer using semiconducting Yttrium Barium Copper Oxide (YBCO) as the infrared sensing material. To investigate the effect of encapsulation on the detectors, the device fabrication sequence was interrupted twice and the microbolometers were characterized. The bolometer figures of merit, thus obtained, were compared to vacuum self-packaged, but non-micromachined bolometers. The self-packaged devices demonstrated voltage responsivities of 7.9x10³ V/W with a temperature coefficient of resistance of -2.5% K^-1, and a thermal conductivity of 2.95x10^-6 W/K. The measured bolometric figures of merit were similar in air and in vacuum, indicating vacuum integrity of the packaged cavity.

Suitable materials as well as various dimensions in the vacuum cavity were determined using finite element method (FEM) based CoventorWARE®. A vacuum cavity made of ceramic Al₂O₃ has been designed. The theoretical thermal conductivity G_th from the detector to the substrate was computed to be 4.0x10^-6W/K and 1.4x10^-4W/K in vacuum and air respectively. These agree well with the measured characteristics.

The talk will cover the design, fabrication and characterization of device-level vacuum packaged microbolometers.

Biography:

Zeynep Çelik-Butler is Professor of Electrical Engineering and Director of Nanotechnology Research and Teaching Facility at the University of Texas at Arlington. She received dual B.S. degrees in electrical engineering and physics from Bogaziçi University, Istanbul, Turkey, in 1982. She received the M.S. and Ph.D. degrees in electrical engineering in 1984 and 1987, respectively, from the University of Rochester. She was an IBM Pre-doctoral Fellow from 1983 to 1984, and an Eastman Kodak Pre-doctoral Fellow from 1985 to 1987. She joined the Department of Electrical Engineering at Southern Methodist University in 1987 as an Assistant Professor; was tenured and promoted to Associate Professor in 1993. Dr. Çelik-Butler was the holder of J. Lindsay Embrey Trustee Assistant Professorship from 1990 to 1993. She served as the Assistant Dean of Graduate Studies and Research from 1996 to 1999. She moved to University of Texas at Arlington in 2002.

She served in various technical committees including 1988, 1989 IEEE-IEDM's and Annual Symposia on Electronic Materials, Processing and Characterization (1989 - 1992) and International Conference on Noise in Physical Systems and 1/f Fluctuations (1993, 1999, 2001). She was the General Chair of TEXMEMS II Workshop. She was the co-Chairman for the SPIE Conf. on Noise in Devices and Circuits in the Symp. on Fluctuation and Noise (FaN'2003) and the symposium co-chair for the same symposium in 2005 (FaN’2005). Currently, she is an editor for Fluctuation and Noise Letters.

Prof. Çelik-Butler has received several awards including the IEEE-Dallas Section Electron Devices Society Outstanding Service Awards (1995, 1997), IEEE - Electron Devices Society, Service Recognition Award (1995), Outstanding Electrical Engineering Graduate Faculty Awards (1996, 1997, 2001), and SMU- Sigma Xi Research Award (1997). Her research interests include microelectromechanical systems, infrared detectors, noise in semiconductor and superconductor devices, and high T_c-superconductivity. She has four patents, four book chapters, and over 130 journal and conference publications in these fields. Dr. Çelik -Butler’s research has been supported by the NSF, SRC, NASA, TEHCB, Motorola, Legerity, ST-Microelectronics, Texas Instruments, Raytheon and ARO.

Dr. Çelik-Butler is a senior member of IEEE, member of Eta Kappa Nu, and the American Physical Society. She is a Distinguished Lecturer for the IEEE-Electron Devices Society.