-
[show abstract]
[hide abstract]
ABSTRACT: In this paper, the application of an in situ stress measurement technique to a silicon nitride thin film deposited onto a thick silicon substrate is presented. The method is based on the measurement of the displacement field originated when a slot is milled into the material under study. Displacements are obtained by digital correlation analysis of scanning electron microscope (SEM) images, whereas milling is performed by ion milling in focused ion-beam equipment. Due to the mechanical constraint introduced by the substrate and the small thickness of the tested layer, the displacements generated by the milling process are in the range 0–5 nm, which is one of the smallest displacement ranges measured up to now in a relaxation-based measurement technique. The local stress value determined with this new method is in good agreement with values obtained by a classical method like the wafer bending test.
Nanotechnology 10/2006; 17(20):5264. · 3.98 Impact Factor
-
[show abstract]
[hide abstract]
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.
Applied Physics Letters 02/2006; 88(7):071910-071910-3. · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper, the authors present a new approach to residual stress measurement that takes advantage of the combined imaging–milling capabilities of focused ion-beam equipment. The method is based on the measurement of the displacement field originated when a slot of a few microns is milled on the material under study. The fitting of the experimental results with an analytical model together with the independent determination of Young's modulus allows us to find the residual stress of the layer under study. The complete experimental procedure is described and its feasibility is demonstrated on a LPCVD silicon nitride micromachined membrane. Values obtained by this new method show a good agreement with values obtained by a classical method such as the bulge test.
Journal of Micromechanics and Microengineering 01/2006; 16(2):254. · 2.11 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This paper describes a novel approach of stress measurement based on the combined imaging–milling capabilities of a FIB equipment. This technique consists on the scaling down of two measurement techniques based on stress-relaxation, the slot and the hole-drilling methods. The main aspects of both approaches at a microscale are described and illustrated and some examples of their application to thin films are presented.
Microelectronic Engineering.
-
[show abstract]
[hide abstract]
ABSTRACT: Design, manufacturing and packaging of new MEMS/NEMS devices demands detailed know-how on mechanical material properties used. Because of size effects due to miniaturization as well as manufacturing and exploitation influences on material properties, classical methods of material testing often do not provide correct material data. Values published by different authors and determined on various devices can differ by ,e.g., a factor of three and more for the same material. Consequently, a strong need exists to measure material properties directly on MEMS devices or MEMS precursor structures. -- Respectively, the authors present a new approach, fibDAC, which allows to measure and analyze deformation fields on stressed micro and nano components, which can be utilized for mechanical material haracterization. The method bases on digital image correlation algorithms (DIC) applied locally to load state images captured in focused ion beam (fib) equipment. As a result, deformation fields are determined, which occur due to loading of MEMS structures inside the FIB station. Combining measured fields with finite element simulations relevant mechanical material properties can be evaluated. Corresponding object loading is accomplished either externally by testing modules designed for application inside the FIB equipment or by FIB specimen treatment in order to release inherent specimen stresses. A similar tool, called microDAC/nanoDAC, has been reported earlier [1,2] and applies DIC techniques to SEM or AFM images. The advantages of the new fibDAC approach occur in the incorporation of specimen preparation (ion milling, ion beam surface polishing and DIC patterning), specimen loading by ion milling and DIC deformation measurement in a single equipment. -- The authors present several applications of fibDAC measurements on stressed micro components. Emphasis is made to the evaluation of residual stresses on micro component structures. "Smart" ion milling is used to cause local deformations resulting from inherent residual stresses. Their analysis gives access to quantified residual stresses. Although being not completely nondestructive the method possesses advantages against other approaches, like e.g. built-in stress sensing structures, because of its more general suitability with regard to quite different structures and residual stress states.
Fraunhofer IZM.
