Athanasios J. Syllaios

Amorphous Silicon Microbolometer Technology

Highly sensitive hydrogenated amorphous silicon (a-Si:H) microbolometer arrays have been developed that take advantage of the high temperature coefficient of resistance (TCR) of aSi:H and its relatively high optical absorption coefficient. TCR is an important design parameter and depends on material properties such as doping concentration. Ultra-thin (∼2000 A) aSiN x :H/a-Si:H/ a-SiN x :H membranes with low thermal mass suspended over silicon readout integrated circuits are built using RF plasma enhanced chemical vapor deposition (PECVD) and surface micromachining techniques. The IR absorptance of the bolometer detectors is enhanced by using quarter-wave resonant cavity structures and thin-film metal absorber layers. To ensure high thermal isolation the microbolometer arrays are vacuum packaged using wafer level vacuum packaging. Imaging applications include a 120×160 a-Si:H bolometer pixel array IR camera operating at ambient temperature. Non-imaging applications are multi-channel detectors for gas sensing systems.

Low-cost low-power uncooled 120x160 a-Si-based microinfrared camera for law enforcement applications

Low power and low cost are primary requirements for an imaging infrared camera serving law enforcement applications. These include handheld, vehicle and helmet mounted systems for search and surveillance applications. In this paper, a 120 X 160 amorphous silicon (a-Si) microbolometer-based uncooled infrared camera technology offering a low cost, low power solution to infrared surveillance for UGS applications is presented. A 120 X 160 micro infrared camera has been demonstrated which exhibits a noise equivalent temperature difference sensitivity approximately 50 mK using f/1 optics and approximately 80 mK using f/1.2 optics. This sensitivity has been achieved without the use of a thermoelectric cooler for array temperature stabilization thereby significantly reducing the power requirements.

Small pixel a-Si/a-SiGe bolometer focal plane array technology at L-3 Communications

Recent developments in low-noise, high temperature coefficient of resistance (TCR) amorphous silicon and amorphous silicon germanium material have led to the development of uncooled focal plane arrays, with TCR in the range 3.2%/K to 3.9%/K, which has been leveraged in the small pixel FPA development at L-3 EOS. In the 17μm pixel technology node at present, 1024x768, 640×480, and 320x240 FPAs have thus far been developed. All three formats employ waferlevel vacuum packaging, with the 1024x768 representing the largest format uncooled FPA wafer-level packaged to date. FPA results from all three formats will be discussed and images will be presented.

Low-power uncooled 120x160 a-Si-based micro infrared camera for unattended ground sensor applications

Low power and low cost are primary requirements for an imaging infrared camera used in unattended ground sensor arrays. In this paper, a 120 X 160 amorphous silicon (a- Si) microbolometer-based uncooled infrared camera technology offering a low cost, low power solution to infrared surveillance for UGS applications is presented. A 120 X 160 micron infrared camera (MIRC) has been demonstrated which exhibits an f/1 noise equivalent temperature difference sensitivity approximately 63 mK. This sensitivity has been achieved without the use of a thermoelectric cooler for array temperature stabilization thereby significantly reducing the power requirements. Chopperless camera operation at a 20 Hz frame rate with power consumption of 380 mW has also been demonstrated. The 120 X 160 MIRC operates under digital signal processor (DSP) control. To reduce cost, this DSP-controlled architecture employs commercial off-the-shelf DSP, A/D, memory and voltage regulator chips. The detector chip, employing an integrating amplifier per unit cell ROIC design, is the single custom chip used. The camera also employs low cost f/1 optics, as well as low cost wafer-level vacuum packaging. In this paper, a-Si microbolometer technology for the MIRC will be presented. Also, the key features and performance parameters of the MIRC are presented.