Millions of micro electro mechanical system sensors are fabricated each year using an ultra-clean process that allows for a vacuum-encapsulated cavity. These devices have a multi-layer structure that contains hidden layers with highly doped silicon, which makes common imaging techniques ineffective. Thus, examining device features post-fabrication, and testing, is a significant challenge. Here, we use a combination of micro- and nano-scale x-ray computed tomography to study device features and assess failure mechanisms in such devices without destroying the ultra-clean cavity. This provides a unique opportunity to examine surfaces and trace failure mechanisms to specific steps in the fabrication process.
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J. Martin: High Volume Manufacturing and Field Stability of MEMS Products: Springer Handbook of Nanotechnology (Springer-Verlag, Berlin, Germany, 2007), pp. 1749–1776.
M. Perlmutterand S. Breit: In The future of the MEMS inertial sensor performance, design and manufacturing, DGON Inertial Sensors and Syst, Karlsruhe, 2016; pp. 1–12.
P.J. de Veen, C. Bos, D.R. Hoogstede, C.Th. A. Revenberg, J. Liljeholm, and T. Ebefors: High-resolution x-ray computed tomography of through silicon vias for RF MEMS integrated passive device applications. Microelectron. Reliab. 55, 1644 (2015).
C.A. Manier, K. Zoschke, H. Oppermann, D. Ruffieux, S. Dalla Piazza, T. Suni, J. Dekker, and G. Allegato: In Vacuum packaging at wafer level for MEMS using gold-tin metallurgy, European Microelectronics Packaging Conf, Grenoble, 2013; pp. 1–8.
Y. Wang: High-Resolution 3D Imaging and Material Analysis with Transmission X-Ray Microscopy and Nano-Ct: Characterization of Materials (John Wiley and Sons, Hoboken, 2012), pp. 1–10.
M. Bajura, G. Boverman, J. Tan, G. Wagenbreth, C.M. Rogers, M. Feser, J. Rudati, A. Tkachuk, S. Aylward, and P. Reynolds: In Imaging Integrated Circuits with x-ray Microscopy, Proc. 36th GOMACTech Conf, Florida, USA, 2011.
E. Zschech, W. Yun, and G. Schneider: High-resolution x-ray imaging-a powerful nondestructive technique for applications in semiconductor industry. Appl. Phys. A 92, 423 (2008).
C. Wyon: X-ray metrology for advanced microelectronics. Eur. Phys. J. Appl. Phys. 49, 20101 (2010).
J. Deng, Y.P. Hong, S. Chen, Y.S. Nashed, T. Peterka, A.J. Levi, J. Damoulakis, S. Saha, T. Eiles, and C. Jacobsen: Nanoscalex-ray imaging of circuit features without wafer etching. Phys. Rev. 695, 104111 (2017).
E. Zschech and A. Diebold: In Metrology and failure analysis for 3D IC integration, AIP Conf. Proc, 2011; pp. 233–239.
A. Partridge and M. Lutz: In Episeal pressure sensor and method for making an episeal pressure sensor. U.S. Patent #6928879 (2005).
R.N. Candler, M.A. Hopcroft, B. Kim, W.-T. Park, R. Melamuf, M. Agarwal, G.Y.A. Partridge, M. Lutz, and T.W. Kenny: Long-term and accelerated life testing of a novel single-wafer vacuum encapsulation for MEMS resonators. J. Microelectromech. Syst. 15, 1446 (2006).
B. Kim, R.N. Candler, M.A. Hopcroft, M. Agarwal, W.-T. Park, and T. W. Kenny: Frequency stability of wafer-scale film encapsulated silicon based MEMS resonators. Sens Actuators A 136, 125 (2007).
E. Ng, H.K. Lee, C.H. Ahn, R. Melamud, and T.W. Kenny: In Stability measurements of silicon MEMS resonant thermometers, 2011 IEEE Sensors Proc, Limerick, 2011; pp. 1257–1260.
Y. Yang, E.J. Ng, Y. Chen, L.B. Flader, and T.W. Kenny: A unified epi-seal process for fabrication of high-stability microelectromechanical devices. J. Microelectromech. Syst. 25, 489 (2016).
Y. Chen, L.B. Flader, D.D. Shin, C.H. Ahn, J. Rodriguez, and T.W. Kenny: Robust method of fabricating epitaxially encapsulated MEMS devices with large gaps. J. Microelectromech. Syst. 26, 1235 (2017).
L.B. Flader, Y. Chen, D.D. Gerrard, and T.W. Kenny: In Wafer-scale encapsulation of fully differential electrodes for mutli-axis inertial sensing, IEEE Transducers Proc, Kaohsiung, 2017; pp. 591–594.
D.B. Heinz, V.A. Hong, C.H. Ahn, E.J. Ng, Y. Yang, and T.W. Kenny: Experimental investigation into stiction forces and dynamic mechanical anti-stiction solutions in ultra-clean encapsulated MEMS devices. J. Microelectromech. Syst. 25, 469 (2016).
R. Maboudian and R. T. Howe: Critical review: adhesion in surface micro-mechanical structures. J. Vac. Sci. Technol. 615, 1 (1997).
Y. X. Zhuang and A. Menon: On the stiction of MEMS materials. Tribol. Lett 19, 111 (2005).
D.M. Tanner, J.A. Walraven, K. Helgesen, L.W. Irwin, F. Brown, N.F. Smith, and N. Masters: In MEMS reliability in shock environments, (Proc. 38th Annual IEEE Int. Reliability Physics Symp.), 2000; pp. 129–138.
V.A. Hong, S. Yoneoka, M.W. Messana, A.B. Graham, J.C. Salvia, T. T. Branchflower, E. Ng, and T.W. Kenny: Fatigue experiments on single crystal silicon in an oxygen-free environment. J. Microelectromech. Syst. 24, 351 (2015).
C.L. Muhlstein, E.A. Stach, and R.O. Ritchie: A reaction-layer mechanism for the delayed failure of micron-scale polycrystalline silicon structural films subjected to high-cycle fatigue loading. Acta Mater. 50, 3579 (2002).
B.L. Henke, E.M. Gullikson, and J.C. Davis: X-ray interactions: photoab-sorption, scattering, transmission, and reflection at E = 50-30000 eV, Z = 1-92. At. Data Nucl. Data Tables 54, 181 (1993).
Y. Liu, F. Meirer, P.A. Williams, J. Wang, J.C. Andrews, and P. Pianetta: TXM-Wizard: a program for advanced data collection and evaluation in full-field transmission x-ray microscopy. J. Synchroton. Radiat 19, 281 (2012).
D.L. Christensen, C.H. Ahn, V.A. Hong, E.J. Ng, Y. Yang, B.J. Lee, and T.W. Kenny: In Hermetically encapsulated differential resonant accelerometer, 2013 Transducers & Eurosensors: Solid-State Sensors, Actuators and Microsystems, 2013; pp. 606–609.
D.D. Shin, C.H. Ahn, Y. Chen, D.L. Christensen, L.B. Flader, and T. W. Kenny: In Environmentally robust differential resonant accelerometer in a wafer-scale encapsulation process, 2017 IEEE MEMS Proceedings, Las Vegas, 2017; pp. 17–20.
L.B. Flader, Y. Chen, D.D. Shin, D.B. Heinz, L. Comenencia Ortiz, A. L. Alter, W. Park, K.E. Goodson, and T.W. Kenny: In Micro-tethering for in-process stiction mitigation of highly compliant structures, 2017 IEEE MEMS Proceedings, Las Vegas, 2017; pp. 675–678.
M.M. Lee, J. Yao and M.C. Wu: In Silicon profile transformation and side-wall roughness reduction using hydrogen annealing, IEEE MEMS, 2005; pp. 596–599.
This work was supported by the Defense Advanced Research Projects Agency (DARPA) Precision Navigation and Timing program (PNT) managed by Dr. Ron Polcawich under contract # N66001-12-1-4260. The fabrication work was performed at the Stanford Nanofabrication Facility (SNF), which was supported by the National Science Foundation through the National Nanotechnology Infrastructure Network under Grant ECS-9731293. The author would also like to thank the National Science Foundation and the Graduate Research Program (NSF-GRFP). Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the US Department of Energy Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515.
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Ortiz, L.C., Heinz, D.B., Flader, I.B. et al. Assessing failure in epitaxially encapsulated micro-scale sensors using micro and nano x-ray computed tomography. MRS Communications 8, 275–282 (2018). https://doi.org/10.1557/mrc.2018.70