Fracture testing of silicon microcantilever beams

Abstract

Silicon microcantilever beams are fractured and characterized. The specially designed beams, etched into two wafers, are loaded to fracture in bending using a unique measurement system. A finite element model of the beams is created, and ABAQUS is used to calculate the displacements and stresses produced by an applied load force. A special testing scheme is devised to obtain certain model parameters: E͗110͘, the Young's modulus along the length of the beam and L force , the position of the applied force. With these parameters defined, the model is well correlated with that of the experimental data. The fracture stress ͑strength͒ of the beam is obtained from the stress produced in the model at the fracture location by a load equivalent to the experimental fracture force. This fracture stress can be used as a design parameter for silicon micromechanical structures. Numerous beams are fractured from both the front and back sides of the wafer, and statistical fracture strength results are compiled for each of these cases. The fracture strength of the front side, 3.3 GPa ͑average͒, is significantly greater than that of the backside, 1.0 GPa ͑average͒. This dissimilarity is attributed to the differences in the surface roughness of these sides.

Dynamic testing of micromechanical structures under thermo-electro-mechanical influences

“…Several of the important techniques include: the microtension test where the fracture strengths and Young's modulus can be estimated for non-integrated free standing structures [7][8][9]; the axisymmetric plate bend test is primarily used to measure the fracture strengths of relatively thick microstructures [10,11]; the microbeam bend test where a concentrated load is used to deflect the microstructure and is used for measuring Young's modulus, yield and fracture strengths of the microdevice [12,13]; the M-test where an electrostatic force is applied to bend thin microstructures in order to obtain experimental characteristics for Young's modulus and residual stresses [14,15]; the wafer curvature measurement method is used primarily for the quantification of residual stresses [16,17]; dynamic (resonance frequency) tests are suitable for measuring Young's modulus of elasticity and residual stresses in both thick and thin free standing microstructures [18][19][20][21]. These approaches require that the MEMS structure be excited in some fashion from its rest position and the changes measured either optically (interferometer, Doppler shift) or electrically (capacitive, resistive), for example.…”

Dimension effect on mechanical behavior of silicon micro-cantilever beams

“…The results showed that both testing methods and brittleness of the silicon lead to the variation of strength. Wilson et al [4] found that there is variation of bending strength of the SCS micro cantilever beam tested from front surface (3.3 GPa) and from back surface (1.0 GPa) due to anisotropic etching on the back surface. Detailed studies of the influence of chemical solution in wet etching on tensile strength of SCS were done by Taechung [5].…”

Analysis of the practical force accuracy of electromagnet-based nanoindenters

“…The nanoindenter has become a main measurement tool in recent years in the micro/nano-mechanics and materials field owing to its capability for high resolution force measurements [1][2][3][4]. There are several types of nanoindenters, for example, MTS Nano Indenter Ò (incorporated into Agilent in 2008), Hysitron TriboIndenter Ò , CSM Nano Hardness Tester Ò , MML NanoTest Ò and CSIRO UMIS Ò .…”