A systematic reliability investigation of the dielectric charging process in electrostatically actuated MEMS based on Kelvin probe force microscopy

This paper presents a comprehensive investigation for the dielectric charging problem in electrostatically actuated microelectromechanical system (MEMS) devices. The approach is based on Kelvin probe force microscopy (KPFM) and targets, in this specific paper, thin PECVD silicon nitride films for electrostatic capacitive RF MEMS switches. KPFM has been employed in order to mimic the potential induced at the dielectric surface due to charge injection through asperities. The effect of dielectric thickness has been investigated through depositing SiNx films with different thicknesses. Then, in order to simulate the different scenarios of dielectric charging in real MEMS switches, SiNx films have been deposited over thermally grown oxide, evaporated gold and electroplated gold layers. Also, the effect of the deposition conditions has been investigated through depositing dielectric films using low and high frequency PECVD methods. The investigation reveals that thin dielectric films have larger relaxation times compared to thick ones when the same injection bias is applied, independently of the substrate nature. For the same SiNx film thickness, the decay time constant is found to be smaller in dielectric films deposited over metallic layers compared to the ones deposited over silicon substrates. Finally, the material stoichiometry is found to affect the surface potential distribution as well as the relaxation time constant.

[1]  Patrick Pons,et al.  Charging-Effects in RF capacitive switches influence of insulating layers composition , 2006, Microelectron. Reliab..

[2]  J. Cazaux,et al.  Reliability modeling of capacitive RF MEMS , 2005, IEEE Transactions on Microwave Theory and Techniques.

[3]  A. Aberle,et al.  Carrier recombination at silicon–silicon nitride interfaces fabricated by plasma-enhanced chemical vapor deposition , 1999 .

[4]  G. Papaioannou,et al.  Temperature study of the dielectric polarization effects of capacitive RF MEMS switches , 2005, IEEE Transactions on Microwave Theory and Techniques.

[5]  K. Müllen,et al.  Quantitative Measurement of the Local Surface Potential of π‐Conjugated Nanostructures: A Kelvin Probe Force Microscopy Study , 2006 .

[6]  J.C.M. Hwang,et al.  Modeling and characterization of dielectric-charging effects in RF MEMS capacitive switches , 2005, IEEE MTT-S International Microwave Symposium Digest, 2005..

[7]  Vittorio Foglietti,et al.  Dual frequency PECVD silicon nitride for fabrication of CMUTs' membranes , 2006 .

[8]  Patrick Pons,et al.  Kelvin probe microscopy for reliability investigation of RF-MEMS capacitive switches , 2008, Microelectron. Reliab..

[9]  P. Soussan,et al.  Influence of the substrate on the lifetime of capacitive RF MEMS switches , 2008, 2008 IEEE 21st International Conference on Micro Electro Mechanical Systems.

[10]  C. W. Pearce,et al.  Characteristics of silicon nitride deposited by plasma‐enhanced chemical vapor deposition using a dual frequency radio‐frequency source , 1992 .

[12]  Michael Hietschold,et al.  Parasitic charging of dielectric surfaces in capacitive microelectromechanical systems (MEMS) , 1998 .

[13]  A. Stemmer,et al.  Resolution and contrast in Kelvin probe force microscopy , 1998 .

[14]  Andreas Stemmer,et al.  Surface potential mapping: A qualitative material contrast in SPM , 1997 .

[15]  J. Papapolymerou,et al.  Effect of deposition conditions on charging processes in SiNx: Application to RF-MEMS capacitive switches , 2009 .

[16]  Robert Plana,et al.  ESD failure signature in capacitive RF MEMS switches , 2008, Microelectron. Reliab..

[17]  Hiroshi Yokoyama,et al.  Scanning maxwell stress microscope for nanometre-scale surface electrostatic imaging of thin films , 1994 .

[18]  J. Boogaard,et al.  Current‐stress induced asymmetry in hydrogenated amorphous silicon n‐i‐n devices , 1992 .

[19]  P. Pons,et al.  A novel low cost failure analysis technique for dielectric charging phenomenon in electrostatically actuated MEMS devices , 2010, 2010 IEEE International Reliability Physics Symposium.

[20]  Patrick Pons,et al.  Voltage and temperature effect on dielectric charging for RF-MEMS capacitive switches reliability investigation , 2008, Microelectron. Reliab..

[21]  Patrick Pons,et al.  Dielectric charging in silicon nitride films for MEMS capacitive switches: Effect of film thickness and deposition conditions , 2009, Microelectron. Reliab..

[22]  Patrick Pons,et al.  Structure dependent charging process in RF MEMS capacitive switches , 2007, Microelectron. Reliab..

[23]  S. Glunz,et al.  Observation of multiple defect states at silicon–silicon nitride interfaces fabricated by low-frequency plasma-enhanced chemical vapor deposition , 1997 .

[24]  Rampi Ramprasad,et al.  Phenomenological theory to model leakage currents in metal–insulator–metal capacitor systems , 2003 .

[25]  Peter G. Steeneken,et al.  Characterization of dielectric charging in RF MEMS capacitive switches , 2006, ICMTS 2006.

[26]  J. Schmitz,et al.  Kelvin probe study of laterally inhomogeneous dielectric charging and charge diffusion in RF MEMS capacitive switches , 2008, 2008 IEEE International Reliability Physics Symposium.

[27]  A. Stemmer,et al.  Practical aspects of Kelvin probe force microscopy , 1999 .