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Proceedings Paper

High-performance long wave infrared bolometer fabricated by wafer bonding
Author(s): Adriana Lapadatu; Gjermund Kittilsland; Anders Elfving; Erling Hohler; Terje Kvisterøy; Thor Bakke; Per Ericsson
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Paper Abstract

A novel microbolometer with peak responsivity in the longwave infrared region of the electromagnetic radiation is under development at Sensonor Technologies. It is a focal plane array of pixels with a 25μm pitch, based on monocrystalline Si/SiGe quantum wells as IR sensitive material. The novelty of the proposed 3D process integration comes from the choice of several of the materials and key processes involved, which allow a high fill factor and provide improved transmission/absorption properties. Together with the high TCR and low 1/f noise provided by the thermistor material, they will lead to bolometer performances beyond those of existing devices. The thermistor material is transferred from the handle wafer to the read-out integrated circuit (ROIC) by wafer bonding. The low thermal conductance legs that connect the thermistor to the ROIC are fabricated prior to the transfer bonding and are situated under the pixel. Depending on the type of the transfer bonding used, the plugs connecting the legs to the thermistor are made before or after this bonding, resulting in two different configurations of the final structure. Using a low temperature oxide bonding and subsequent plugs formation result in through-pixel plugs. Pre-bonding plugs formation followed by thermo-compression bonding result in under-pixel plugs. The pixels are subsequently released by anhydrous vapor HF of the sacrificial oxide layer. The ROIC wafer containing the released FPAs is bonded in vacuum with a silicon cap wafer, providing hermetic encapsulation at low cost. Antireflection coatings and a thin layer getter are deposited on the cap wafer prior to bonding, ensuring high performance of the bolometer.

Paper Details

Date Published: 4 May 2010
PDF: 12 pages
Proc. SPIE 7660, Infrared Technology and Applications XXXVI, 766016 (4 May 2010); doi: 10.1117/12.852526
Show Author Affiliations
Adriana Lapadatu, Sensonor Technologies AS (Norway)
Gjermund Kittilsland, Sensonor Technologies AS (Norway)
Anders Elfving, Sensonor Technologies AS (Norway)
Erling Hohler, Sensonor Technologies AS (Norway)
Terje Kvisterøy, Sensonor Technologies AS (Norway)
Thor Bakke, SINTEF (Norway)
Per Ericsson, Acreo AB (Sweden)

Published in SPIE Proceedings Vol. 7660:
Infrared Technology and Applications XXXVI
Bjørn F. Andresen; Gabor F. Fulop; Paul R. Norton, Editor(s)

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