High quantum efficiency annular backside silicon photodiodes for reflectance pulse oximetry in wearable wireless body sensors

Sune Bro Duun, Rasmus Grønbek Haahr, Ole Hansen, Karen Birkelund, Erik Vilain Thomsen

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    The development of annular photodiodes for use in a reflectance pulse oximetry sensor is presented. Wearable and wireless body sensor systems for long-term monitoring require sensors that minimize power consumption. We have fabricated large area 2D ring-shaped silicon photodiodes optimized for minimizing the optical power needed in reflectance pulse oximetry. To simplify packaging, backside photodiodes are made which are compatible with assembly using surface mounting technology without pre-packaging. Quantum efficiencies up to 95% and area-specific noise equivalent powers down to 30 fW Hz(-1/2) cm(-1) are achieved. The photodiodes are incorporated into a wireless pulse oximetry sensor system embedded in an adhesive patch presented elsewhere as 'The Electronic Patch'. The annular photodiodes are fabricated using two masked diffusions of first boron and subsequently phosphor. The surface is passivated with a layer of silicon nitride also serving as an optical filter. As the final process, after metallization, a hole in the center of the photodiode is etched using deep reactive ion etch.
    Original languageEnglish
    JournalJournal of Micromechanics and Microengineering
    Volume20
    Issue number7
    ISSN0960-1317
    DOIs
    Publication statusPublished - 2010

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