Preparation of Porous Metal Membrane by Thermal Annealing for Thin Film Encapsulation

Authors: Jaibir Sharma, Lee JaeWung, Merugu Srinivas, Navab Singh

Abstract:

This paper presents thermal annealing de-wetting technique for the preparation of porous metal membrane for Thin Film Encapsulation (TFE) application. Thermal annealing de-wetting experimental results reveal that pore size formation in porous metal membrane depend upon i.e. 1. The substrate at which metal is deposited, 2. Melting point of metal used for porous metal cap layer membrane formation, 3. Thickness of metal used for cap layer, 4. Temperature used for formation of porous metal membrane. In order to demonstrate this technique, Silver (Ag) was used as a metal for preparation of porous metal membrane on amorphous silicon (a-Si) and silicon oxide. The annealing of the silver thin film of various thicknesses was performed at different temperature. Pores in porous silver film were analyzed using Scanning Electron Microscope (SEM). In order to check the usefulness of porous metal film for TFE application, the porous silver film prepared on amorphous silicon (a- Si) and silicon oxide was released using XeF2 and VHF, respectively. Finally, guide line and structures are suggested to use this porous membrane for robust TFE application.

Keywords: De-wetting, thermal annealing, metal, melting point, porous.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1108156

References:

[1] G. H. Mohamed, The MEMS Handbook, 2nd ed., New York, USA: Taylor & Francis, 2002.
[2] M. Perlmutter and L. Robin High-Performance, “Low Cost Inertial MEMS: A Market in Motion!” Position Location and Navigation Symposium (PLANS), 2012, pp.225-229.
[3] R. R. Tummala and E. J. Rymaszewski “Microelectronics Packaging Handbook”, 2nd ed., Massachustts, USA: Kluwer Academic Publishers 1989.
[4] K. Najafi, "Micropackaging Technologies for Integrated Microsystems: Applications to MEMS and MOEMS", Micromaching and Microfabrication Process Technology VII, Proc. Of SPIE Vol. 4979, 2003, pp.1-19.
[5] Lutz M. Partridge, B. Kim, M. Hopcroft, R. N. Candler, T.W. Kenny, “MEMS Resonators: Getting the Packaging Right”, in: SEMICONJapan, 2005.
[6] H. Stark and K. Najafi, “A Low-Temperature Thin-Film Electroplated Metal Vacuum Package”, J. Microelectromech. Syst., vol. 13, 2004, pp. 147–157.
[7] V. Lindroos, M. Tilli, A. Lehto and T. Motooka, Handbook of Silicon Based MEMS Materials and Technologies, 1st ed., Elsevier, chap 38, 2010, pp. 569-574.
[8] J. L. Pornin, C. Gillot, G. Parat, F. Jacquet, E. Lagoutte, N. Sillon, G. Poupon, F. Dumont, “Wafer Level Thin Film Encapsulation for BAW RF MEMS.”, Electronic Components and Technology Conference, 2007, pp. 605-609.
[9] C. Gillot, J.L. Pornin, A. Amaud, E. Lagoutte, N.Sillon, J.C. Souriau, “Wafer Level Thin Film Encapsulation for MEMS”, Electronic Components and Technology Conference , 2005, pp. 243-247.
[10] US patent 7,344,907 B2 Mar. 18, 2008
[11] C. O’Mahony, M. Hill, Z. Olszewski and A. Blake, “Wafer-Level Thin- Film Encapsulation for MEMS”, Microelectronic Engineering vol. 86, 2009, pp. 1311–1313.
[12] R.H. Rico, B. Du Bois, A. Witvrouw, C. Van Hoof, J.-P. Celis, “Fabrication of Porous Membranes for MEMS Packaging by One-Step Anodization in Sulfuric Acid”, J. Electrochem. Soc. 154 (9) K74 – K78, 2007.
[13] J. Zekey, S. D Tezcan, J.-P. Celis, R. Puers, C. Van Hoof, and H.A.C. Tilmans, “Wafer-Level Thin Film Vacuum Packages for MEMS using Nanoporous Anodic Alumina Membrane”, Transducers conference, 2011, pp. 975-977.
[14] B. K. Lee, D. H. Choi and J. B. Yoon “Use of nanoporous columnar thin film in the wafer level packaging of MEMS devices” J. Micromech. Microeng. 20 045002 (9pp), 2010.
[15] W. I. Jang, C. A. Choi, M. L. Lee, C. H. Jun and Y. T. Kim “Fabrication of MEMS devices by using anhydrous HF gas-phase etching with alcoholic vapor” J. Micromech. Microeng. 12, 297–306, 2002.