成果報告書詳細
管理番号20110000001150
タイトル*平成22年度中間年報 ナノテク・先端部材実用化研究開発/ナノシリコンによる広帯域デジタル音源の開発
公開日2011/9/9
報告書年度2010 - 2010
委託先名株式会社カンタム14 国立大学法人東京農工大学 株式会社メムス・コア
プロジェクト番号P05023
部署名電子・材料・ナノテクノロジー部
和文要約和文要約等以下本編抜粋:1. 研究開発の内容及び成果等 昨年度に引き続き、ナノシリコンによる広帯域デジタル音源の実用化に向けて、音源素子としては広帯域熱音響素子の開発、音源素子の小面積化、音源素子の薄型化、の3点について検討を行い(分担:(株)カンタム14)、並行してデジタル駆動による高効率化技術の検討を行った(分担:東京農工大学)。また、4インチ径のシリコン基板を用いたシリコン半導体プロセスによる素子化プロセス技術を開発した(分担:(株)メムス・コア)。これらにより、熱音響素子評価およびサンプル供給の準備が進展し、また、そのために必要な問題点が明らかになった。
英文要約(1) Development of Broad Band Acoustic Device
To realize the structure of broad-band acoustic device based on nanosilicon, which was designed last year, the anodization conditions to obtain nanosilicon layers thicker than 100μm were studied and optimized on various types of Si substrates using the equipment for 4-inch-diam wafers installed last year. By applying optimum anodization condition followed by supercritical drying process it became possible to obtain a thick stress-released nanosilicon layer with adequate porosity.
(2) Development of Small-Size Device
In principle, thermo-acoustic sound emitter can be down-sized keeping similar sound quality level in wider band-width range. The effect of anodization conditions on acoustic characteristics was studied as a function of sound emission area down to 1 x 1 mm2. It was confirmed that the basic acoustic characteristics kept unchanged down to the target device size of <10 x 10 mm2. Even for digital operation, the effective acoustic efficiency was found to increase with decreased device size.
(3) Development of Thin Device
In contrast with any conventional mechanical speakers, the device structure of our approach is the one that can be assembled intimately contact with the holding substrate. This feature enables us to fabricate sound emitting device thinner than 0.5mm which is the target of the project. Through the evaluation of acoustic characteristics of nanosilicon speakers fabricated on 300μm thick Si wafer, it was reconfirmed that the final device thickness will meet the target even if we take the thermal diffuser thickness into account.
(4) Efficiency Improvement of Thermo-acoustic Devices by Digital Operation
To realize digital driving of the sound emitter based on the outstanding impulse response, a pulse density modulation (PDM) driver circuit was designed and installed. The maximum operation frequency of the PDM driver is 500kHz and has 10bit resolution for 100Hz-100kHz acoustic modulation. The spectrum analysis of the emitted sound from a nanosilicon device showed that the sound pressure level at the frequency of the original driving signal was the main component in 300Hz-100kHz range, and PDM operation was confirmed to work.
(5) Development of Manufacturing Process for Thermo-acoustic Devices
As the physical property of nanosilicon varies with conduction type and conductivity as well as anodization conditions. In addition, to meet the sound frequency requirement down to 100Hz the required nanosilicon layer becomes as thick as 100μm. Device manufacturing process for thick nanosilicon layer was studied extensively. Several special processes has been developed and applied to fabricate heater patterns on thick, high-porosity nanosilicon layer. As a consequence, a basic full manufacturing process of thermo-acoustic device from 4-inch wafer to the sound emitting device assembled on TO-8 header has been established in this year.
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