A 'nano-battering ram' for measuring surface forces: obtaining force–distance curves and sidewall stiction data with a MEMS device

MEMS (micro-electromechanical systems) devices often suffer from stiction induced reliability problems. Although a theoretical framework to describe stiction in MEMS is under development in the scientific community, experimental data are still scarce. We have developed a MEMS device that can be used to electronically measure sidewall surface forces in situ, i.e. on chip. To be able to use it, we have developed a sensitive electronic readout system that detects comb drive capacitance variations with 10 aF resolution. In addition, we use a model to correct the measured capacitance changes for the ground-plane-induced levitation effect of the comb drive. Our first results for the interaction between oxidized polycrystalline silicon sidewall surfaces show that at a relative humidity (RH) of 45% and a temperature of 27 °C the stiction force amounts to 6.7 ± 1.6 kPa, which we assume to be mainly caused by capillary condensation. This stiction force was found to be independent of both the normal force with which the surfaces were pressed against each other prior to the stiction measurement and the age of the contact, showing that the contact is fully elastic, and capillary condensation is instantaneous on the time scale of the measurement (milliseconds to seconds). We also use the device to measure complete force–distance curves, so that these results can be compared with AFM (atomic force microscope) measurements.

[1]  R. Howe,et al.  Alkyltrichlorosilane-based self-assembled monolayer films for stiction reduction in silicon micromachines , 1998 .

[2]  K. Komvopoulos,et al.  An experimental study of sidewall adhesion in microelectromechanical systems , 2005, Journal of Microelectromechanical Systems.

[3]  Tjerk H. Oosterkamp,et al.  A sensitive electronic capacitance measurement system to measure the comb drive motion of surface micromachined MEMS devices , 2007 .

[4]  B. Bhushan,et al.  Three-Dimensional Dry/Wet Contact Analysis of Multilayered Elastic/Plastic Solids With Rough Surfaces , 2006 .

[5]  William C. Tang,et al.  Electrostatic Comb Drive Levitation And Control Method , 1992 .

[6]  W. Merlijn van Spengen,et al.  MEMS reliability from a failure mechanisms perspective , 2003, Microelectron. Reliab..

[7]  Kukjin Chun,et al.  A sticking model of suspended polysilicon microstructure including residual stress gradient and postrelease temperature , 1998 .

[8]  R. Howe,et al.  Critical Review: Adhesion in surface micromechanical structures , 1997 .

[9]  C. Mastrangelo,et al.  A simple experimental technique for the measurement of the work of adhesion of microstructures , 1992, Technical Digest IEEE Solid-State Sensor and Actuator Workshop.

[10]  W. Merlijn van Spengen,et al.  A method to extract the lateral and normal components of motion from the capacitance change of a moving MEMS comb drive , 2007 .

[11]  T. Chung,et al.  A new organic modifier for anti-stiction , 2001 .

[12]  A. Polycarpou,et al.  Adhesion and contact modeling and experiments in microelectromechanical systems including roughness effects , 2006 .

[13]  Bharat Bhushan,et al.  Adhesion and stiction: Mechanisms, measurement techniques, and methods for reduction , 2003 .

[14]  R. Legtenberg,et al.  Stiction in surface micromachining , 1996 .

[15]  Roya Maboudian,et al.  An investigation of sidewall adhesion in MEMS , 2003 .

[16]  R. Puers,et al.  A physical model to predict stiction in MEMS , 2006 .

[17]  Terry A. Michalske,et al.  Accurate method for determining adhesion of cantilever beams , 1999 .

[18]  Maarten P. de Boer,et al.  Role of interfacial properties on MEMS performance and reliability , 1999, Industrial Lasers and Inspection.

[19]  Jean W. Zu,et al.  Modeling of dry stiction in micro electro-mechanical systems (MEMS) , 2006 .