1. A NOVE LOW-TEMPERATURE MICROCAP PACKAGING USING SU-8 BONDING Y.K. Kim, S.W. Kim, and B.K. Ju Korea,Chungju National,Chungju and University,KOREA Tranducer 2007 報告人： 蘇聖欽

2. Outline Motivation Packaging Design Fabrication Process Experimental Details And Results Conclusion References

3. Outline Motivation Packaging Design Fabrication Process Experimental Details And Results Conclusion References

4. Motivation MEMS packaging is much more expensive, heavy and large than in case of integrated circuits packaging. MEMS often reaches more than 70% of the total cost of the microsystem. Higher temperature may damage metallization layers and cause considerable stress in the bonded materials.

5. Outline Motivation Packaging Design Fabrication Process Experimental Details And Results Conclusion References

6. Structure Design A cavity with desired thickness is formed for cap structure by using KOH wet etching. Dimensions of the microcap are determined such that the width and the length are 800 and 1100um.

7. Material Properties The proposed packaging method used the polymer as a cap structure and the intermediate adhesive layer. YK Kim, SH Yi, SW Kim, BK Ju, “A Novel Low-Temperature Microcap Packaging Using SU-8 Bonding”,2007.

8. Outline Motivation Packaging Design Fabrication Process Experimental Details And Results Conclusion References

9. Packaging process KOH at 80 ℃ (70um) Silicon oxide(8um) SU-8 spin coated Exposure and bake(95 ℃ ) Via holes by DRIE Gold by electroplating Bonding by heating and pressure Cu deposited

10. SU-8 photoresist process The finally optimized recipes of SU-8 photoresist are shown in under table. YK Kim, SH Yi, SW Kim, BK Ju, “A Novel Low-Temperature Microcap Packaging Using SU-8 Bonding”,2007.

11. Outline Motivation Packaging Design Fabrication Process Experimental Details And Results Conclusion References

12. Bonding Strength The bonding strength of the bonded pair for various bonding temperatures was measured by pull testing. Fig. shows the tensile test curves under different bonding temperatures. The maximum strength is 15.7 MPa at 120 ℃. YK Kim, SH Yi, SW Kim, BK Ju, “A Novel Low-Temperature Microcap Packaging Using SU-8 Bonding”,2007.

13. Packaging Results The thickness of the microcap and cavity were 50um and 30um. Polymers are by far more permeable to gas and moisture than ceramics or metal sealants. They investigated sputtering copper films(1um) as a diffusion barrier. YK Kim, SH Yi, SW Kim, BK Ju, “A Novel Low-Temperature Microcap Packaging Using SU-8 Bonding”,2007.

14. Outline Motivation Packaging Design Fabrication Process Experimental Details And Results Conclusion References

15. Conclusion This method provides a simple process, easy assembly and low temperature processing. The optimal bonding temperature was 120 ℃. SU-8 adhesive bonding shows a strong bonding tensile strength about 7-17MPa.

16. References YK Kim, SH Yi, SW Kim, BK Ju, “A Novel Low-Temperature Microcap Packaging Using SU-8 Bonding”, Actuators and Microsystems Conference pp. 2107 – 2110, 2007. A. R. Mirza, “wafer-level packaging technology for MEMS”, The 7th IEEE Intersoc. ConF. Thermal and Thermomechanical Phenomena in Electronic Systems., vol. 2, pp. 113-119, 2000. F. Niklaus, P.Enoksson, E. Kalvesten, G. Stemme, “Low temperature full wafer adhesive bonding of structured wafers”, J. Micromech. Microeng. Vol. 11 pp. 100-107, 2001.