Low-cost uncooled infrared detectors in CMOS process

Date

2003-12-01

Author

Eminoglu, S
Tezcan, DS
Tanrikulu, MY
Akın, Tayfun

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This paper reports the implementation and comparison of two low-cost uncooled infrared microbolometer detectors that car be implemented using standard n-well CMOS processes. One type is based on a suspended n-well resistor, which is implemented in a 0.8 mum CMOS process and has a pixel size of 80 mum x 80 mum with a fill factor of 13%; and the other type is based on a suspended p(+)-active/n-well diode, which is implemented in a 0.35 mum CMOS process and has a pixel size of 40 mum x 40 mum with a fill factor of 44%. These detectors can be obtained with simple bulk-micromachining processes after the CMOS fabrication, without the need for any complicated lithography or deposition steps. The diode type detector has a measured dc responsivity (R) of 4970 V/W at 20 muA bias and a thermal time constant of 35.8 ms at 80 mTorr vacuum level, and it has a measured rms noise of 0.52 muV for a 4 kHz bandwidth, resulting in a detectivity (D*) of 9.7 x 10(8) cm Hz(1 /2)/W. The resistive n-well detector can provide the same dc responsivity at 1.68 V detector bias voltage, with about 10 times more self-heating as compared to that of the diode type detector. This detector has a measured rms noise of 0.81 RV for a 4 kHz bandwidth, resulting in a detectivity (D*) of 8.9 x 10(8) cm Hz(1/2)/W, which can be improved further with higher detector bias voltages at the expense of increased self-heating. The diode type detector is better for low-cost large format infrared detector arrays, since it has a superior response even at reduced pixel sizes and lower biasing levels.

Subject Keywords

Instrumentation, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Condensed Matter Physics, Metals and Alloys

URI

https://hdl.handle.net/11511/46196

Collections

Department of Electrical and Electronics Engineering, Article