Due to the rapid development of IC technology the traditional packaging concepts are making a transition into more complex system integration techniques in order to enable the constantly increasing demand for more functionality, performance, miniaturisation and lower cost. These new packaging concepts (as e.g. system in package, 3D integration, MEMS-devices) will have to combine smaller structures and layers made of new materials with even higher reliability. As these structures will more and more display nano-features, a coupled experimental and simulative approach has to account for this development to assure design for reliability in the future. A necessary “nano-reliability” approach as a scientific discipline has to encompass research on the properties and failure behaviour of materials and material interfaces under explicit consideration of their micro- and nano-structure and the effects hereby induced. It uses micro- and nano-analytical methods in simulation and experiment to consistently describe failure mechanisms over these length scales for more accurate and physically motivated lifetime prediction models. This paper deals with the thermo-mechanical reliability of microelectronic components and systems and methods to analyse and predict it. Various methods are presented to enable lifetime prediction on system, component and material level, the latter promoting the field of nano-reliability for future packaging challenges in advanced electronics system integration.

Lifetime modelling for microsystems integration: from nano to systems

Nano-reliability measures the ability of a nano-scaled product to perform its intended functionality. At the nano scale, the physical, chemical, and biological properties of materials differ in fundamental, valuable ways from the properties of individual atoms, molecules, or bulk matter. Conventional reliability theories need to be restudied to be applied to nano-engineering. Research on nano-reliability is extremely important due to the fact that nano-structure components account for a high proportion of costs, and serve critical roles in newly designed products. This review introduces the concepts of reliability to nano-technology; and presents the current work on identifying various physical failure mechanisms of nano-structured materials, and devices during fabrication process, and operation. Modeling techniques of degradation, reliability functions, and failure rates of nano-systems are also reviewed in this work.

A Review of Reliability Research on Nanotechnology

This paper reports a new technique, namely the incremental micro-hole-drilling method (IμHD) for mapping in-plane residual or applied stresses incrementally as a function of depth at the micron-scale laterally and the sub-micron scale depth-wise. Analogous to its macroscale counterpart, it is applicable either to crystalline or amorphous materials, but at the sub-micron scale. Our method involves micro-hole milling using the focused ion beam (FIB) of a dual beam FEGSEM/FIB microscope. The resulting surface displacements are recorded by digital image correlation of SEM images recorded during milling. The displacement fields recorded around the hole are used to reconstruct the stress profile as a function of depth. In this way residual stresses have been characterized around a drilled hole of 1.8microns. diameter, enabling the profiling of the stress variation at the sub-micron scale to a depth of 1.8 microns. The new method is used to determine the near surface stresses in a (peened) surface-severe-plastically-deformed (S2PD) Zr50Cu40Al10 (in atomic percent, at.%) bulk metallic glass bar. In plane principal stresses of -800 MPa ± 90 MPa and −600 MPa ± 90 MPa were measured, the maximum compressive stress being oriented 15° to the axis of the bar.

Micron-Scale Residual Stress Measurement by Micro-Hole Drilling and Digital Image Correlation

Quantification of residual stress gradients can provide great improvements in understanding the complex interactions between microstructure, mechanical state, mode(s) of failure and structural integrity. Highly focused local probe non-destructive techniques such as X-ray diffraction, electron diffraction or Raman spectroscopy have an established track record in determining spatial variations in the relative changes in residual stress with respect to a reference state for many structural materials. However, the interpretation of these measurements in terms of absolute stress values requires a strain-free sample often difficult to obtain due to the influence of chemistry, microstructure or processing route. With the increasing availability of focused ion beam instruments, a new approach has been developed which is known as the micro-scale ring-core focused ion beam-digital image correlation technique. This technique is becoming the principal tool for quantifying absolute in-plane residual stresses. It can b...

A state-of-the-art review of micron-scale spatially resolved residual stress analysis by FIB-DIC ring-core milling and other techniques

The expanding and developing fields of micro-electromechanical systems (MEMS) and nano-electromechanical (NEMS) are highly interdisciplinary and rely heavily on experimental mechanics for materials selection, process validation, design development, and device characterization. These devices range from mechanical sensors and actuators, to microanalysis and chemical sensors, to micro-optical systems and bioMEMS for microscopic surgery. Their applications span the automotive industry, communications, defense systems, national security, health care, information technology, avionics, and environmental monitoring. This chapter gives a general introduction to the fabrication processes and materials commonly used in MEMS/NEMS, as well as a discussion of the application of experimental mechanics techniques to these devices. Mechanics issues that arise in selected example devices are also presented.

A Brief Introduction to MEMS and NEMS

The rapid development of a wide variety of new devises in microelectronics, MEMS, NEMS and nano technology will lead to new challenges for their mechanical characterization and reliability assessment. Measurement of deformations and stresses in microscopic and even nanoscopic regions becomes a key issue. The authors make use of load state images captured by Atomic Force Microscopes (AFM) in order to measure object deformations. Out-of-plane deformation is determined from usual topography scans by computing surface profile differences. NanoDAC, a recently established approach, allows to meet these goals with regard to in-plane deformation. The method bases on cross correlations analysis performed on AFM scans, which are captured from thermally and/or mechanically loaded samples. Finally, local 3D displacement fields and in-plane strain fields are measured. A description of the basic principles and the capability of the technique are given. Furthermore, the authors demonstrate the potential of the mentioned method by its application to microcrack evaluation and the study of sensor and MEMS structure degradation. The first application corresponds to the measurement of crack opening displacement in the very vicinity of crack tips. As a consequence, fracture mechanics parameters are derived and allow to assess the defect with regard to possible crack propagation and component failure. This approach is used to study the influence of nanoscale material structures on crack behavior. The second example illustrates how the impact of thermal loading to the constitution of sensor or MEMS submicron layers is investigated by deformation analysis. The devices had been heated actively under the AFM. Degradation processes due to a severe thermal material mismatch were observed and monitored.

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/5045/1/Evaluating-microdefect-structures-by-AFM-based-deformation-measurement/10.1117/12.483826.pdf

Evaluating microdefect structures by AFM-based deformation measurement

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 characterization. The method bases on digital image correlation (DIC) algorithms applied locally to load state images captured from focused ion beam (FIB) equipment. As a result, deformation fields are determined, which occur due to loading of microsystem structures inside the focused ion beam system. A similar tool, called microDAC/nanoDAC, has been reported earlier and applies DIC techniques to SEM or AFM images. The advantages of the new fibDAC approach occur in the incorporation of specimen preparation like ion milling, ion beam surface polishing and DIC patterning as well as specimen loading by ion milling and DIC deformation measurement in a single equipment. Combining measured fields with finite element simulations or analytical solutions of the corresponding mechanical problem, 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 ion milling on the test specimen. As an example ion milling on specimens with residual stresses is demonstrated. Released in this way residual stresses cause object deformations nearby the milling area. Measured deformation fields by fibDAC allow to evaluate very local residual stresses. Some principal experiments illustrate the feasibility of the chosen approach. Features and challenges connected with this new method are discussed in some detail.

FIB based measurements for material characterization on MEMS structures

With the development of micro- and nanotechnological products such as sensors, MEMS/NEMS and their broad application in a variety of market segments new reliability issues will arise. The increasing interface-to-volume ratio in highly integrated systems and
nanoparticle filled materials and unsolved questions of size effect of nanomaterials are challenges for experimental reliability evaluation. To fulfill this needs the authors developed the nanoDAC method (nano Deformation Analysis by Correlation), which allows the
determination and evaluation of 2D displacement fields based on scanning probe microscopy (SPM) data. In-situ SPM scans of the analyzed object are carried out at different thermo-mechanical load states. The obtained topography-, phase- or error-images are
compared utilizing grayscale cross correlation algorithms. This allows the tracking of local image patterns of the analyzed surface structure. The measurement results of the nanoDAC method are full-field displacement and strain fields. Due to the application of
SPM equipment deformations in the micro-, nanometer range can be easily detected. The method can be performed on bulk materials, thin films and on devices i.e microelectronic components, sensors or MEMS/NEMS. Furthermore, the characterization and evaluation of
micro- and nanocracks or defects in bulk materials, thin layers and at material interfaces can be carried out.

Characterization of microcracks by application of digital image correlation to SPM images

With ongoing miniaturization from micro electronic mechanical systems (MEMS) towards nano electronic mechanical systems (NEMS), there is a need for new reliability concepts making use of meso-type (micro to nano) or fully nanomechanical approaches. For the development of theoretical descriptions and their numerical implementation on the basis of simulation tools experimental verification will be of major interest. Therefore, there is a need for measurement techniques with capabilities of determination and evaluation of strain fields with very local (nanoscale) resolution. Following this challenge the authors developed the nanoDAC method (nano Deformation Analysis by Correlation) which enables the extraction of nanoscale displacement fields from scanning probe microscopy (SPM) images. Components of interest are thermomechanically loaded under the SPM and topography scans of the critical areas are taken at specific load states. The obtained images are analyzed by digital image correlation resulting into full-field displacement and strain fields. Due to the application of SPM equipment deformations in the micro-, nanometer range can be easily detected. The method can be performed on bulk materials, thin films and on devices i.e microelectronic components, sensors or MEMS/NEMS. Furthermore, the characterization and evaluation of micro- and nanocracks or defects in bulk materials, thin layers and at material interfaces can be carried out. In combination with finite element simulations the application of the described experimental method to sensor elements is a promising approach for reliability analysis of newly designed sensor architectures.

Nanoscale Deformation Measurements for Reliability Analysis of Sensors

The paper comprises research results obtained for stress determination on micro and nanotechnology components. It 
meets the concern of controlling stresses introduced to sensors, MEMS and electronics devices during different 
micromachining processes. The method bases on deformation measurement options made available inside focused ion 
beam equipment. Removing locally material by ion beam milling existing stresses / residual stresses lead to deformation 
fields around the milled feature. Digital image correlation techniques are used to extract deformation values from 
micrographs captured before and after milling. In the paper, two main milling features have been analyzed - through 
hole and through slit milling. Analytical solutions for stress release fields of in-plane stresses have been derived and 
compared to respective experimental findings. Their good agreement allows to settle a method for determination of 
residual stress values, which is demonstrated for thin membranes manufactured by silicon micro technology. Some 
emphasis is made on the elimination of main error sources for stress determination, like rigid body object displacements 
and rotations due to drifts of experimental conditions under FIB imaging. In order to illustrate potential application 
areas of the method residual stress suppression by ion implantation is evaluated by the method and reported here.

Juergen Keller

Papers

Evaluating microdefect structures by AFM-based deformation measurement

FIB based measurements for material characterization on MEMS structures

Characterization of microcracks by application of digital image correlation to SPM images

Nanoscale Deformation Measurements for Reliability Analysis of Sensors

FIB-based measurement of local residual stresses on microsystems