1 / 24

MEMS Rigid Diaphragm Speaker

MEMS Rigid Diaphragm Speaker. Scott Maghy Tim Havard Sanchit Sehrawat. Macro-scale. Try to make MEMS device based on same concept. Motivation. Few similar products Small size Clandestine Privacy Low power Potential lower cost Highly customizable performance No surgery!.

porter-cobb
Download Presentation

MEMS Rigid Diaphragm Speaker

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MEMS Rigid Diaphragm Speaker Scott Maghy Tim Havard SanchitSehrawat

  2. Macro-scale Try to make MEMS device based on same concept

  3. Motivation • Few similar products • Small size • Clandestine • Privacy • Low power • Potential lower cost • Highly customizable performance • No surgery!

  4. Current Hearing Devices • Few speakers that fit completely inside the ear • Some piezoelectric speakers • Bone conduction speaker for above the ear: 1 inch long • CMOS MEMS speakers exits, and are being developed • Several hearing devices • Downsides: • Require surgery • Much larger • Cost • Complexity

  5. Implantable Hearing Devices • Cochlear Implants • Auditory Brainstem implants • Implantable Middle-ear devices • Piezoelectric devices • Electromagnetic devices

  6. Cochlear Implants Auditory Brainstem Implants Source: http://www.nidcd.nih.gov/health/hearing/coch.asp

  7. Piezoelectric Devices • Operation • Advantage: inert in a magnetic field • Disadvantage: Power output directly related to size of crystal. Example: • Middle Ear Transducer (MET)

  8. Middle Ear Transducer • Translates electrical signals into mechanical motion to directly stimulate the ossicles

  9. Middle Ear Transducer Remote MET Implant Charger

  10. Electromagnetic Devices • Operation • Small magnet is attached to vibratory structure in ear • Only partially implantable – coil must be housed externally. Sizes of coil & magnet restricted by ear anatomy. • Power decreases as the square of the distance between coil & magnet – coil & magnet must be close

  11. Vibrant Soundbridge Magnet surrounded by coil

  12. Ridged Diaphragm MEMS Speaker

  13. Materials • Polysilicon: structural material for cantilever and diaphragm • Silicon Oxide: for sacrificial layers • Silicon Nitride: isolation of wafer • Gold: electrodes and electrical connections

  14. Fabrication Deposit layers of Electrodes, oxide, and photoresist (as shown) Deposit Silicon Nitride Layer Pattern photoresist & then etch electrodes & oxide using RIE Deposit Oxide 2 layer

  15. Fabrication Coat columns with Photoresist and etch away remaining oxide 2 Remove photoresist from electrode 2 Etch oxide 2, and make Poly-Si columns Deposit oxide 3 as shown Remove photoresist and deposit Poly-Si

  16. Fabrication Make Poly-Si diaphragm base thicker Release oxide layers

  17. Performance and Optimization

  18. Speaker Mechanics Force balance: Fspring + +/- Felect where and Setting

  19. Acoustic Modeling Sinusoidal input voltage: Drives diaphragm displacement: Which causes sound intensity: Acoustic power can then be obtained: Note: system parameters can be tailored to be significantly below the resonant frequency.

  20. Observed Acoustic Power • Sound intensity decays quadratically with distance  This results in limited effective speaker range

  21. Comparison of Acoustic Sound Power Decreasing frequency Device is in the threshold of human hearing!

  22. Improvements • Implement a process that allows for sealing of speaker cone to support • This would give better acoustic properties • Could be accomplished by CMOS MEMS procedure • Fabricate cone shape with stamping method to achieve better shape and more cost effective fabrication

  23. Improvement Cont. • Further research into materials for the cantilevers to decrease stiffness of cantilevers • This would allow greater diaphragm displacement and therefore greater intensity • Other materials exist with lower Young’s modulus that would accomplish this but fabrication is suspect • Other methods of securing the diaphragm • “Spring” attachment • Decrease the mass of the diaphragm by altering fabrication process

  24. QUESTIONS

More Related