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Thin Film Polymer Stress Measurement Using Piezoresistive Anisotropically Etched Pressure Sensors

Published online by Cambridge University Press:  21 February 2011

David J. Monk  and
Mahesh Shah
David J. Monk
Affiliation:
Motorola, Semiconductor Products Sector, Sensor Products Division, M/D D138, 5005 E. McDowell Rd., Phoenix, AZ 85008
Mahesh Shah
Affiliation:
Motorola, Semiconductor Products Sector, Sensor Products Division, M/D D138, 5005 E. McDowell Rd., Phoenix, AZ 85008
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Abstract

Stresses in thin polymer films have been studied for some time by using wafer bowing, bending beams, microstructure release, and laser holographic techniques. An alternative technique for measuring stresses in thin films is discussed in the following paper. Piezoresistive anisotropically etched single crystal silicon pressure sensors are sensitive not only to applied pressure, but also to applied package stress. Deposited passivation materials, like silicone gels and polyimides, have been observed to change the sensitivity of the pressure sensor. In the current work, a thin, conformal polymeric coating (parylene C) is being developed for these pressure sensors. This thin film has been observed to reduce the sensitivity of the device as a function of the film thickness and modulus and the silicon thickness and modulus. The parylene C thin films exhibit a consistent change in film stress during annealing indicating a modification to polymer crystallinity and a corresponding change in material properties. Qualitatively, the electrical output on the pressure sensor compares favorably with measurements taken using wafer bowing. Experimental DMA and TMA work has been performed to determine the modulus (7.84 × 105 psi) and CTE (39 ppm/°C at 25 °C) of the material. However, literature values of modulus (4.1 × 105 psi) have been used with finite element analysis to model the stress effect more accurately for the thin conformal coating on the pressure sensor device. These results indicate that the sensitivity of the pressure sensor will be reduced approximately quadratically as a function of the polymer coating thickness. An empirical function has been derived to estimate sensitivity loss as a function of substrate (i.e., initial diaphragm material) modulus and thickness and coating modulus and thickness.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 390: Symposium S – Electronic Packaging Materials Science VIII , 1995 , 103
Copyright
Copyright © Materials Research Society 1995

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References

REFERENCES

1. Thin Films: Stresses and Mechanical Properties IV, edited by Townsend, P. H., Weihs, T. P., Sanchez, J. , J. E. and Børgesen, P. (Mater. Res. Soc. Proc., 308, Pittsburgh, PA, 1993).Google Scholar
2. Biernath, R. W. and Soane, D. S., in Polymeric Materials for Electronics Packaging and Interconnection, edited by Lupinski, J. H. and Moore, R. S. (American Chemical Society, Los Angeles, CA, 1989), p. 356.Google Scholar
3. Biernath, R. W., Ph.D. Thesis, University of California, Berkeley, 1990.Google Scholar
4. Monk, D. J., He, Y. and Soane, D. S., in Manufacturing Processes and Materials Challenges in Microelectronics Packaging, edited by Chen, W. T., Engel, P., and Jahsman, W. E. (ASME Winter Annual Meeting, Atlanta, GA, 1991), p. 87.Google Scholar
5. Soane, D. S., Solid State Technology, 165, (May, 1989).Google Scholar
6. Soane, D. S., Chem. Eng. Prog., 86, 28, (April, 1990).Google Scholar
7. Monk, D. J., He, Y. and Soane, D. S., in Thin Films: Stresses and Mechanical Properties IV, edited by Townsend, P. H., Weihs, T. P., Sanchez, J. , J. E. and Børgesen, P. (Mat. Res. Soc. Symp. Proc., 308, Pittsburgh, PA, 1992), p. 175.Google Scholar
8. Allen, M. G., Mehrehany, M., Howe, R. T. and Senturia, S. D., Appl. Phys. Lett., 51, 241, (1987).Google Scholar
9. Maden, M. A. and Farris, R. J., in Electronic Packaging Materials Science IV, (MRS, San Diego, CA, 1989), p. 143.Google Scholar
10. Young, W. C. and Roark, R. J., Formulas for Stress and Strain, (McGraw-Hill, New York, 1982).Google Scholar
11. Pourahmadi, F., Barth, P. and Petersen, K., Sensors and Actuators, A21–A23, 850, (1990).Google Scholar
12. Pourahmadi, F., Sensors and Materials, 6, 193, (1994).Google Scholar
13. Giachino, J. M., in The 7th International Conference on Solid-State Sensors and Actuators, (Yokohama, Japan, 1993), p. 982.Google Scholar
14. Fiedler, L. D., Knapp, T. L., Norris, A. W. and Virant, M. S., in Society of Automotive Engineers International Congress and Exposition, (Dow Corning Corporation, Detroit, MI, 1990).Google Scholar
15. Shin-Etsu, , “Shin-Etsu Fluorosilicone RTV,” 1990.Google Scholar
16. Nitto, , “General Properties of MP-3000F3S,” Product Specifications, 1991.Google Scholar
17. Maudie, T., Appliance Magazine, to be published, (1995).Google Scholar
18. Maudie, T. and Wertz, J., in International Appliance Technical Conference, (Champaign/Urbana, IL, 1995), to be presented.Google Scholar
19. Olson, R., Circuits Manufacturing, 26, 57, (1986).Google Scholar
20. Olson, R., in International Symposium on Microelectronics, (1986), p. 236.Google Scholar
21. Kale, V. S. and Riley, T. J., in Electronic Components Conference, (Arlington, VA, 1977), p. 245.Google Scholar
22. Kale, V. S., in Electronic Components Conference, (Anaheim, CA, 1978), p. 344.Google Scholar
23. Olson, R., in 1985 Electrical/Electronics Insulation Conference, (IEEE, Boston, MA, 1985), p. 288.Google Scholar
24. Baker, T. E., Bagdasarian, S. L., Fix, G. L. and Judge, J. S., J. Electrochem. Soc., 124, 897, (1977).Google Scholar
25. Gorham, W. F., J. Polym. Sci., 4, 3027, (1966).Google Scholar
26. Olson, R., Surf. Mount Tech., 37, (January, 1991).Google Scholar
27. Wong, C. P., in Material Research Society Symposium, (MRS, Boston, MA, 1988), p. 175.Google Scholar
28. Beach, W. F., Lee, C., Bassett, D. R., Austin, T. M. and Olson, R., “Xylylene Polymers,” Encyclopedia of Polymer Science and Engineering (John Wiley), p. 990.Google Scholar
29. Niegisch, W. D. and Gorham, W. F., “Xylylene Polymers,” Encyclopedia of Polymer Science and Technology, (John Wiley & Sons, Inc., New York, 1971), p. 98.Google Scholar
30. Bachman, B. J., in 1st International SAMPE Electronics Conference, (SAMPE, Santa Clara, CA, 1987), p. 431.Google Scholar
31. Beach, W. F. and Austin, T. M., SAMPE J., 24, 9, (1988).Google Scholar
32. Pyle, J., Machine Design, 65, 77, (1993).Google Scholar