TY - BOOK

T1 - Residual Stresses and Crack Growth in Microelectronic Thin Films

AU - Konetschnik, Ruth

N1 - no embargo

PY - 2017

Y1 - 2017

N2 - The miniaturization of microelectronic devices has become more and more important over the past few years, with an accompanying increase in complexity. As macroscale tests are not applicable for such small components, miniaturized experiments have to be applied to study the materials response of the complex arrangements used in state-of-the-art and future devices at small length scales. Especially residual stresses can play an important role in thin film systems concerning performance and lifetime, thus they have to be fully accounted when determining fracture mechanical quantities. The present thesis concentrates on recent developments regarding the local determination of residual stresses and their influence on the fracture behaviour of multi-layered thin film stacks. The materials investigated are sputter deposited Cu-W-Cu and W-Cu-W trilayer systems, with an individual layer thickness of 500 nm, on a stress-free Si(100) substrate. Samples are fabricated via cross section polishing and focused ion beam (FIB) milling. Initially, the residual stress depth profiles are determined by means of the ion beam layer removal (ILR) method that was further improved in this work concerning depth resolution. The stress profile is calculated from the deflection of a cantilever that changes when parts of the film are removed. Subsequently, fracture experiments perpendicular to the interface are performed in-situ in the scanning electron microscope (SEM) to obtain comprehensive knowledge of the fracture process and toughness. An accompanying finite element based modelling approach is introduced to determine crack-driving forces in the presence of interfaces and residual stresses, clearly demonstrating their important influence. Finally, fracture experiments parallel/along the interfaces are conducted applying different existing and novel miniaturized testing techniques. By analyzing the incorporated interfaces systematically the benefits and challenges of the individual techniques are discussed, and as a final conclusion it is suggested to evaluate strong interfaces such as the W-Cu interface by applying a novel micro shear test, where the failing interface is predefined by the sample geometry. With the gained results the importance of elastic and plastic incompatibilities and residual stresses is emphasized when addressing fracture mechanical quantities of multi-layered thin film systems. Furthermore, the relevance of novel and sophisticated micromechanical test methods is underlined by the findings of this thesis.

AB - The miniaturization of microelectronic devices has become more and more important over the past few years, with an accompanying increase in complexity. As macroscale tests are not applicable for such small components, miniaturized experiments have to be applied to study the materials response of the complex arrangements used in state-of-the-art and future devices at small length scales. Especially residual stresses can play an important role in thin film systems concerning performance and lifetime, thus they have to be fully accounted when determining fracture mechanical quantities. The present thesis concentrates on recent developments regarding the local determination of residual stresses and their influence on the fracture behaviour of multi-layered thin film stacks. The materials investigated are sputter deposited Cu-W-Cu and W-Cu-W trilayer systems, with an individual layer thickness of 500 nm, on a stress-free Si(100) substrate. Samples are fabricated via cross section polishing and focused ion beam (FIB) milling. Initially, the residual stress depth profiles are determined by means of the ion beam layer removal (ILR) method that was further improved in this work concerning depth resolution. The stress profile is calculated from the deflection of a cantilever that changes when parts of the film are removed. Subsequently, fracture experiments perpendicular to the interface are performed in-situ in the scanning electron microscope (SEM) to obtain comprehensive knowledge of the fracture process and toughness. An accompanying finite element based modelling approach is introduced to determine crack-driving forces in the presence of interfaces and residual stresses, clearly demonstrating their important influence. Finally, fracture experiments parallel/along the interfaces are conducted applying different existing and novel miniaturized testing techniques. By analyzing the incorporated interfaces systematically the benefits and challenges of the individual techniques are discussed, and as a final conclusion it is suggested to evaluate strong interfaces such as the W-Cu interface by applying a novel micro shear test, where the failing interface is predefined by the sample geometry. With the gained results the importance of elastic and plastic incompatibilities and residual stresses is emphasized when addressing fracture mechanical quantities of multi-layered thin film systems. Furthermore, the relevance of novel and sophisticated micromechanical test methods is underlined by the findings of this thesis.

KW - dünne Schichten

KW - Eigenspannungen

KW - Bruchfestigkeit

KW - Grenzflächenfestigkeit

KW - Mikromechanik

KW - Physikalische Dampfphasenabscheidung

KW - Finite Elemente Simulation

KW - Multilayer

KW - thin films

KW - residual stress

KW - fracture toughness

KW - interface toughness

KW - small scale mechanics

KW - physical vapour deposition

KW - finite element modelling

KW - multilayer

M3 - Doctoral Thesis

ER -