Megapixel HgCdTe MWIR focal plane array with a 15-μm pitch

CEA/LETI has been working for several years on the development of HgCdTe-based infrared dual band detectors [3]. Since 2001 CEA/LETI is also involved in a large program for the demonstration of dual band QWIP FPAs presenting large format and small pitch. This study is carried out with the QWIP team of THALES Research and Technology (TRT) in charge of QWIP design, MBE growth and GaAs processing for the detector side. As part of this program TRT investigated different quantum structures and pixel architectures for the realization of two-band FPAs for MWIR/LWIR and LWIR/LWIR applications. At the end of this study a choice of the most appropriate architecture was done. On its side, CEA/LETI designed readout circuits optimized for the selected dual-band QWIP. TRT delivered QWIP arrays and CEA/LETI proceeded to the assembly, integration and electro-optical characterization. The aim of this paper is to describe the architecture of these dual-band demonstrators and to present the first results concerning their electro-optical performances measured at 70K and 65K.

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“…This process allows yields extremely high, close to 100% to be achieved routinely on these large FPAs and with pitches as low as 15µm [9].…”

Section: Focal Plane Assemblymentioning

confidence: 96%

Demonstration of 256x256 dual-band QWIP infrared FPAs

et al. 2005

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“…This architecture leads to some symmetry with orthotropic properties: the indium solder bumps are aligned parallel/perpendicular to the edges of the detection circuit. Four main process steps are necessary to manufacture the detector (all steps are described in [16] ): the indium bump depositing on the silicon circuit, the hybridisation of the CdHgTe detection circuit, the underfilling step and the final detection circuit thinning. During the hybridisation step, heating until 430 K is applied (above indium melting temperature); then both mechanical and chemical polishings of the detector circuit are performed to keep the active detection CdHgTe layer very thin compared to the thickness of the silicon circuit.…”

Section: Presentation Of the Detector Architecturementioning

confidence: 99%

“…During hybridisation, before thinning, the detection circuit consists of two main layers, the CdHgTe epitaxial layer and a CdZnTe substrate [16] . In order to minimise the number of nodes in the model, the presence of the CdZnTe layer was not taken into account in the assembly.…”

Section: Geometric Hypotheses Boundary Conditions and Thermal Loadingsmentioning

confidence: 99%

Multilayer CdHgTe-based infrared detector: 2D/3D microtomography, synchrotron emission and finite element modelling with stress distribution at room temperature and 100 K

2020

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The mechanical behaviour of a CdHgTe-based infrared detector was evaluated after processing at several temperatures to determine the impact of thermomechanical loading on residual stress and reliability. The architecture of the detector was first entirely characterized, relying on SEM, X-ray microtomography and diffraction analysis, in order to get the nature, the morphology and the crystallographic orientation of all the constitutive layers, and in particular the indium solder bumps. The results notably showed the unexpected single crystal aspect of the indium bumps with a repeatable truncated cone geometry. To obtain the thermomechanical response of the structure after processing and in the range of operating temperatures (from 430 K to 100 K), a 3D Finite Element model was then developed. As expected, the numerical results showed a stress gradient evolution in the structure from high to low temperatures, with high loca njvvl stress around 30 MPa in the CdHgTe at 100 K, mainly due to the thermal expansion coefficient mismatch between the different layers. They highlighted the significant influence of the geometry and the single crystal nature of the bumps as well as the behaviour law of the different materials.

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“…Indium bump hybridization of mega pixel arrays was already demonstrated at this pitch ( Figure 8) [18][19] . …”

Section: Designmentioning

confidence: 99%

High-resolution FPAs on MBE-grown HgCdTe/CdTe/Ge

Badano¹,

Ballet²,

Zanatta³

et al. 2005

Detectors and Associated Signal Processing II

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We report on the progress achieved in the molecular beam epitaxy of 3" and 4" HgCdTe on CdTe(211)B/Ge composite substrates, and the subsequent fabrication of high performance focal plane arrays. We first describe the growth of the heterostructures, and their characterization. Then we examine the fabrication of a 1280x1024 small-pitch focal plane array, which shows operability in excess of 99% for both the responsivity and the noise-equivalent thermal difference.

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Megapixel HgCdTe MWIR focal plane array with a 15-μm pitch

Cited by 14 publications

References 5 publications

Demonstration of 256x256 dual-band QWIP infrared FPAs

Demonstration of 256x256 dual-band QWIP infrared FPAs

Multilayer CdHgTe-based infrared detector: 2D/3D microtomography, synchrotron emission and finite element modelling with stress distribution at room temperature and 100 K

High-resolution FPAs on MBE-grown HgCdTe/CdTe/Ge

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