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

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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

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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",
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journal = "Journal of Micromechanics and Microengineering",
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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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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.

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

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JO - Journal of Micromechanics and Microengineering

JF - Journal of Micromechanics and Microengineering

SN - 0960-1317

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