1. 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

2. Outline  Introduction  Material characterization  Device fabrication  Device characterization  Conclusion

3. 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.

4. Introduction (cont.) http://www.indiabiometric.com/products.html http://news.sel.sony.com/es/image_library/b2b/ media_app_systems/detail?asset_id=26642

5. Material characterization Coductive PDMS (CPDMS): Mixture of PDMS and carbon black Gauge factor =(ΔR/R 0 )/σ CPDMS7.4 Constantan alloy2.1 Si120 Piezoresistive sensitivity (Pa ) =(ΔR/R 0 )/ε CPDMS3X10 Si<10 -6 -9

6. Device fabrication 1. Sputter Ti/W and Au electrodes 2. Spin a layer of PR (AZ4620), then pattern the PR.

7. 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.

8. 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.

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

10. Device fabrication (cont.)

11. Device characterization

12. Device characterization (cont.)

13. Conclusion  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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