Measurement of residual stresses in micromachined structures in a microregion

Abstract

The use of a focused ion beam equipment is reported to find out the in-plane residual stress value of a microelectromechanical system structure by performing a local stress release. The ion beam column is used to mill stress-release slots of a few microns, whereas the scanning electron column captures micrographs of the milled area before and after the stress release process. The displacement component perpendicular to the slot is obtained from digital image correlation analysis of the captured high-resolution micrographs. The fitting of the experimental results with an analytical model together with the independent determination of the Young's modulus allows one to find the residual stress value of the layer under study to a very good accuracy

Advanced Experimental and Simulation Approaches to Meet Reliability Challenges of New Electronics Systems

“…As a result residual stresses can be computed. [15][16][17][18] In the past, the authors demonstrated that the extraction of in-plane stress values of thin membranes can be easily carried out measuring local stress relaxations. Tiny through slots milled into the membrane inside a FIB equipment lead to stress relief deformations causing some tens of nanometers slot opening.…”

“…Because the mechanical problem for the displacement field can be solved analytically, a relatively simple parameter fitting allows to compute stress values. [15] Stress measurements in thin layers or layer structures are a more general problem of concern. First attempts to tackle this problem were made by the authors in Refs., [17,18] milling tiny trenches into the layers of interest.…”

Fabrication Technique of Deformation Carriers (Gratings and Speckle Patterns) with FIB for Microscale/Nanoscale Deformation Measurement

“…Korsunsky and Sebastiani et al [19][20][21] applied FIB milling to fabricate periodic holes as speckle patterns for nanoscale measurement. Sabate et al [1,[22][23][24] acquired speckle patterns by deposition of 20 nm pt layer with FIB for nanoscale measurement. With the use of FIB, Kregting et al [25] first defined a rectangular grid in spacing of 250 nm and then randomly positioned markers within a square of 150 nm size around each grid point.…”

Residual Stress Measurement in Micro-region Using Digital Image Correlation Method

“…To better understand the generation of residual stress so as to effectively control the magnitude of residual stress, the techniques to measure residual stress need to be developed for film-matrix structures. At present, the existing measurement techniques mainly include X-ray diffraction [1,2], Raman spectroscopy [3,4] and measuring by the release of residual stress [5][6][7][8][9][10][11][12]. For the former two methods, only the average residual stress within the measured area can be obtained.…”

“…Sabate et al [5][6][7] used FIB to fabricate a hole or a slot at the film surface to release the residual stress and utilized digital image correlation (DIC) to measure residual stress in a film. Massl et al [8] used FIB to process micro cantilever and measured its deflection by DIC to obtain the residual stress of a film.…”