This paper presents a detailed characterization of silicon germanium oxide (Si<sub>x</sub>Ge<sub>y</sub>O<sub>1-x-y</sub>) thin films with an Oxygen
concentration below 10%. The results demonstrated that a high TCR and a low corresponding resistivity can be achieved
using various compositions, for example, Si<sub>0.054</sub>Ge<sub>0.877</sub>O<sub>0.069</sub> film has achieved a TCR and a resistivity of -3.516/K, and
629 Ω-cm, respectively. The lowest measured resistivity and the corresponding TCR were 119.6 Ω-cm and -2.202 %/K
respectively, using Si<sub>0.136</sub>Ge<sub>0.838</sub>O<sub>0.026</sub> for film deposited at room temperature, whereas the highest achieved TCR and the
corresponding resistivity at room temperature were -5.017 %/K, and 39.1×103 Ω-cm, respectively, using
Si<sub>0.167</sub>Ge<sub>0.762</sub>O<sub>0.071</sub> for films deposited at room temperature. The calculated activation energy (E<sub>a</sub>) from the slope of
Arrhenius plots were varied between 0.1232 eV to 0.3788 eV. The X-ray diffraction study demonstrated that the films
are amorphous but did not show any dependence on varying silicon at fixed oxygen concentration. The noise study
demonstrated that these films exhibit relatively high 1/f.
Uncooled amorphous silicon microbolometers have been established as a field-worthy technology for a broad range of
applications where performance and form factor are paramount, such as soldier-borne systems. Recent developments in
both bolometer materials and pixel design at L-3 in the 17μm pixel node have further advanced the state-of-the-art.
Increasing the a-Si material temperature coefficient of resistance (TCR) has the impact of improving NETD sensitivity
without increasing thermal time constant (TTC), leading to an improvement in the NETD×TTC product. By tuning the
amorphous silicon thin-film microstructure using hydrogen dilution during deposition, films with high TCR have been
developed. The electrical properties of these films have been shown to be stable even after thermal cycling to
temperatures greater than 300<sup>o</sup>C enabling wafer-level vacuum packaging currently performed at L-3 to reduce the size
and weight of the vacuum packaged unit. Through appropriate selection of conditions during deposition, amorphous
silicon of ~3.4% TCR has been integrated into the L-3 microbolometer manufacturing flow. By combining pixel design
enhancements with improvements to amorphous silicon thin-film technology, L-3's amorphous silicon microbolometer
technology will continue to provide the performance required to meet the needs to tomorrow's war-fighter.
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.
An important application of thin-film hydrogenated amorphous silicon (α-Si:H) is infrared detection and imaging with
microbolometer focal plane arrays. Key α-Si:H electrical transport properties that influence detector design and
performance are resistivity and temperature coefficient of resistance (TCR). These properties have been measured over
a wide temperature range for p- and n-type doped α-Si:H thin-films deposited by plasma enhanced chemical vapor
deposition using silane as a precursor gas. Resistivity near and above room temperature follows an Arrhenius thermally
activated dependence. At low temperatures, resistivity transitions from Arrhenius behavior to a variable range hopping mechanism described by the Mott relation and TCR changes at a slower rate than predicted by thermally activated transport alone. Resistivity and TCR are affected by doping and film growth parameters such as dilution of the silane precursor with hydrogen. Resistivity decreases with dopant concentration for both p-type and n-type dopants. Resistivity and TCR increase with hydrogen dilution of silane. TCR and resistivity are interrelated and optimization of thin-film preparation and processing is necessary to obtain high TCR with resistivity values compatible with readout integrated circuit designs. Such optimization of transport properties of α-Si:H films has been applied to the development of high performance ambient operating temperature (uncooled) microbolometer arrays.
This paper presents recent developments in next generation microbolometer Focal Plane Array (FPA) technology at L-3 Communications Infrared Products (L-3 CIP). Infrared detector technology at L-3 CIP is based on hydrogenated amorphous silicon (a-Si:H) and amorphous silicon germanium(a-SiGe:H). Large format high performance, fast, and compact IR FPAs are enabled by a
low thermal mass pixel design; favorable material properties; an advanced ROIC design; and wafer level packaging. Currently at L-3 CIP, 17 micron pixel FPA array technology including 320x240,
640 x 480 and 1024 x768 arrays is under development. Applications of these FPAs range from low power microsensors to high resolution near-megapixel imager systems.