chapter  7
68 Pages

Chapter 7

Abstract ............................................................................... 326 7.1 Introduction ................................................................ 327 7.2 Mechanics of Biaxial Stress in Thin Films Rigidly

Bonded to a Substrate ............................................... 330 7.3 Methods of Measurement of Residual Stresses and

Strains in Thin Films ................................................ 334 7.4 Sources of Energetic Particle Bombardment

in PVD.......................................................................... 339 7.5 Review of Key Concepts Relevant to the Atomic Origins

of Intrinsic Residual Stress in Thin Films .............. 343 7.5.1 Universal Binding Energy Relation ............... 344 7.5.2 Fundamentals of Ion Bombardment-Induced

Lattice Defects ................................................. 347 7.6 Stress Evolution Models ............................................ 352

7.6.1 Stress Evolution as a Function of Film Thickness in Non-Energetic Deposition .......................... 352

7.6.2 Stress Evolution during Energetic Particle Bombardment .................................................. 357 7.6.2.1 Correlation between Stresses and

Microstructures .................................. 357 7.6.2.2 Tensile Stress ..................................... 364 7.6.2.3 Compressive Stress ............................. 371 7.6.2.4 Limits of Residual Stress .................. 377

7.7 Other Phenomena Induced by Energetic Particle Bombardment that May Influence the Intrinsic Film Stress .......................................................................... 379 7.7.1 Materials Transport and Ion Mixing ............. 379

7.7.1.1 Recoil Mixing ..................................... 380 7.7.1.2 Cascade Mixing .................................. 381 7.7.1.3 Thermodynamic Effects in Ion

Mixing ................................................. 382 7.7.2 Bombardment-Induced Phase

Transformation ................................................ 384 7.8 Summary .................................................................... 385 Acknowledgments ............................................................... 386 References ............................................................................ 386

ABSTRACT

Many novel thin film or surface treated materials are synthesized by non-equilibrium processes such as those based on physical vapor deposition and energetic ion bombardment. An inherent component of these processes are the residual stresses that are induced during synthesis. Since these stresses strongly influence the properties, performance and long-term reliability of these materials, understanding the mechanisms of stress generation, relaxation and methods of tailoring residual stresses is of great importance. In this article, we present a review of the current literature on stress generation in ion-beam synthesized thin films. In addition, we discuss a unified model of stress evolution in such materials with the intent of developing ways of tailoring stress to meet the needs of future novel materials.