Surface-micromachined silicon air-gap Bragg reflector for thermal infrared

Mikko Tuohiniemi, Martti Blomberg

    Research output: Contribution to journalArticleScientificpeer-review

    13 Citations (Scopus)

    Abstract

    We present a MEMS-based distributed Bragg reflector for thermal infrared (TIR) wavelengths 7 µm < λ < 12 µm. Surface micro-machining process flow was developed for [poly-Si/air-gap/poly-Si] λ/4-mirror using low-pressure chemical-vapour deposited SiO2 as intra-mirror and mirror-to-substrate sacrificial layers. Circular 3 mm diameter mirrors with theoretical reflectance exceeding 99% were designed. Poly-Si layers of the mirror were anchored for retaining constant mutual distance. Anchoring density and mirror-to-substrate gap were varied among samples. We utilized scanning-electron microscope (SEM) imaging for qualitative estimation of processing result success as well as for layer-thickness measurements. We characterized the mirror topography and mechanical response under local point loading by scanning with a stylus profilometer. Fourier-transform IR (FT-IR) spectroscopy was utilized in studies of a reflectance spectrum. A one-dimensional computer simulation was allowed to fit model parameters to FT-IR data. Best-fit thicknesses of air gaps and poly-Si layers were compared with design parameters and with SEM measurements in order to verify the final structure corresponding to the design.
    Original languageEnglish
    Article number075014
    JournalJournal of Micromechanics and Microengineering
    Volume21
    Issue number7
    DOIs
    Publication statusPublished - 2011
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    Bragg reflectors
    Silicon
    Mirrors
    Infrared radiation
    Polysilicon
    Air
    Scanning
    Fourier transforms
    Electron microscopes
    Distributed Bragg reflectors
    Thickness measurement
    Substrates
    Topography
    MEMS
    Hot Temperature
    Infrared spectroscopy
    Machining
    Vapors
    Imaging techniques
    Wavelength

    Cite this

    @article{c1177c1414f8407581cf64a36357206c,
    title = "Surface-micromachined silicon air-gap Bragg reflector for thermal infrared",
    abstract = "We present a MEMS-based distributed Bragg reflector for thermal infrared (TIR) wavelengths 7 µm < λ < 12 µm. Surface micro-machining process flow was developed for [poly-Si/air-gap/poly-Si] λ/4-mirror using low-pressure chemical-vapour deposited SiO2 as intra-mirror and mirror-to-substrate sacrificial layers. Circular 3 mm diameter mirrors with theoretical reflectance exceeding 99{\%} were designed. Poly-Si layers of the mirror were anchored for retaining constant mutual distance. Anchoring density and mirror-to-substrate gap were varied among samples. We utilized scanning-electron microscope (SEM) imaging for qualitative estimation of processing result success as well as for layer-thickness measurements. We characterized the mirror topography and mechanical response under local point loading by scanning with a stylus profilometer. Fourier-transform IR (FT-IR) spectroscopy was utilized in studies of a reflectance spectrum. A one-dimensional computer simulation was allowed to fit model parameters to FT-IR data. Best-fit thicknesses of air gaps and poly-Si layers were compared with design parameters and with SEM measurements in order to verify the final structure corresponding to the design.",
    author = "Mikko Tuohiniemi and Martti Blomberg",
    year = "2011",
    doi = "10.1088/0960-1317/21/7/075014",
    language = "English",
    volume = "21",
    journal = "Journal of Micromechanics and Microengineering",
    issn = "0960-1317",
    publisher = "Institute of Physics IOP",
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    }

    Surface-micromachined silicon air-gap Bragg reflector for thermal infrared. / Tuohiniemi, Mikko; Blomberg, Martti.

    In: Journal of Micromechanics and Microengineering, Vol. 21, No. 7, 075014, 2011.

    Research output: Contribution to journalArticleScientificpeer-review

    TY - JOUR

    T1 - Surface-micromachined silicon air-gap Bragg reflector for thermal infrared

    AU - Tuohiniemi, Mikko

    AU - Blomberg, Martti

    PY - 2011

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    N2 - We present a MEMS-based distributed Bragg reflector for thermal infrared (TIR) wavelengths 7 µm < λ < 12 µm. Surface micro-machining process flow was developed for [poly-Si/air-gap/poly-Si] λ/4-mirror using low-pressure chemical-vapour deposited SiO2 as intra-mirror and mirror-to-substrate sacrificial layers. Circular 3 mm diameter mirrors with theoretical reflectance exceeding 99% were designed. Poly-Si layers of the mirror were anchored for retaining constant mutual distance. Anchoring density and mirror-to-substrate gap were varied among samples. We utilized scanning-electron microscope (SEM) imaging for qualitative estimation of processing result success as well as for layer-thickness measurements. We characterized the mirror topography and mechanical response under local point loading by scanning with a stylus profilometer. Fourier-transform IR (FT-IR) spectroscopy was utilized in studies of a reflectance spectrum. A one-dimensional computer simulation was allowed to fit model parameters to FT-IR data. Best-fit thicknesses of air gaps and poly-Si layers were compared with design parameters and with SEM measurements in order to verify the final structure corresponding to the design.

    AB - We present a MEMS-based distributed Bragg reflector for thermal infrared (TIR) wavelengths 7 µm < λ < 12 µm. Surface micro-machining process flow was developed for [poly-Si/air-gap/poly-Si] λ/4-mirror using low-pressure chemical-vapour deposited SiO2 as intra-mirror and mirror-to-substrate sacrificial layers. Circular 3 mm diameter mirrors with theoretical reflectance exceeding 99% were designed. Poly-Si layers of the mirror were anchored for retaining constant mutual distance. Anchoring density and mirror-to-substrate gap were varied among samples. We utilized scanning-electron microscope (SEM) imaging for qualitative estimation of processing result success as well as for layer-thickness measurements. We characterized the mirror topography and mechanical response under local point loading by scanning with a stylus profilometer. Fourier-transform IR (FT-IR) spectroscopy was utilized in studies of a reflectance spectrum. A one-dimensional computer simulation was allowed to fit model parameters to FT-IR data. Best-fit thicknesses of air gaps and poly-Si layers were compared with design parameters and with SEM measurements in order to verify the final structure corresponding to the design.

    U2 - 10.1088/0960-1317/21/7/075014

    DO - 10.1088/0960-1317/21/7/075014

    M3 - Article

    VL - 21

    JO - Journal of Micromechanics and Microengineering

    JF - Journal of Micromechanics and Microengineering

    SN - 0960-1317

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