Fabrication technology of piezoresistive conductive PDMS for micro

Fabrication technology of piezoresistive conductive PDMS for micro fingerprint sensors IEEE MEMS 2007 Miao Lu, Amine Bermak, Yi-Kuen Lee 學號: 9635517 姓名: 陳立仁

Outline o o o Introduction Material characterization Device fabrication Device characterization Conclusion

Introduction With the progress of computer and internet, our life become more convenient and comfortable. But it is also convenient for hackers. Though, how to keep personal privacy is very important.

Introduction (cont. ) http: //www. indiabiometric. com/products. html http: //news. sel. sony. com/es/image_library/b 2 b/ media_app_systems/detail? asset_id=26642

Material characterization Coductive PDMS (CPDMS): Mixture of PDMS and carbon black Gauge factor =(ΔR/R 0)/σ CPDMS Constantan alloy Si Piezoresistive sensitivity (Pa -1 ) =(ΔR/R 0)/ε 7. 4 -6 CPDMS 3 X 10 Si <10 2. 1 120 -9

Device fabrication 1. Sputter Ti/W and Au electrodes 2. Spin a layer of PR (AZ 4620), then pattern the PR.

Device fabrication (cont. ) 3. Electroplate the mushroom-shaped Au electrodes, then remove the PR. 4. Spin and pattern another layer of PR. Etch electrodes and remove PR.

Device fabrication (cont. ) 5. Spin a layer of PR as a well. Pour the CPDMS on the substrate. 6. Remove the excessive CPDMS. Strip the PR.

Device fabrication (cont. ) 7. Deposit parylene to protect the electrode. 8. Spin and pattern the PR. Etch parylene , then strip the PR.

Device fabrication (cont. )

Device characterization

Device characterization (cont. )

Conclusion o o o The operating pressure range of this device is really close to that of commercial products. If the package is not good enough, the sensing ability will be affected. A well mixtured CPDMS is needed.

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