Abstract:
MEMS devices require active mechanism for tuning in field operation because post fabrication, design parameters may
change due to residual stress, fabrication imperfections, temperature etc. Application of axial compressive (C) or tensile
forces (T) allows one to implement this tuning. Effects of C and T forces, stress gradient (SG) and transverse loading is
analyzed for futuristic materials like Gallium Nitride (GaN) and Silicon Carbide (SiC) for use in high temperatures and
harsh environments. The effects of above forces on pull in voltage (VPI), bandwidth (BW) and resonance frequency (RF)
are analyzed. Results for Aluminum cantilever beam show, that VPI decreases by * 1.2 times at low beam lengths of
200 lm and about 5 times at higher length of 800 lm when T force is changed to C under loading. Similar trends are
holding for GaN and SiC except that VPI scales up in proportion to material’s Young’s modulus E. An analytical relations
of VPI versus E and Poisson’s ratio‘m’ are predicted. Effect of SG is also studied and it is found that although SG affects VPI
within 10% range, application of axial C or T forces further change it within 20% range. Comparison of analytical results
for VPI with Coventorware software shows a better agreement for low loading of 10% compared to full loading of 100%.
Also, Log–Log plot of VPI versus L can be used to estimate the contribution of charge re-distribution and fringing field.
Furthermore, BW decreases by 16 Hz when C is applied and increases by 66 Hz when T is applied for Aluminum
cantilever with 400 lm length and 50 lm width. Similarly, RF decreases by 165 Hz in C and increases by 623 Hz for T
loading. The predictions of our model agree well with experimental and FEM results (within 4.54% and 6.46%
respectively).
