Analysis of Electromigration- and Stress-Induced Dynamical Response of Voids Confined in Metallic Thin Films
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0899-N07-17.1
ANALYSIS OF ELECTROMIGRATION- AND STRESS-INDUCED DYNAMICAL RESPONSE OF VOIDS CONFINED IN METALLIC THIN FILMS M. Rauf Gungor, Jaeseol Cho, and Dimitrios Maroudas Department of Chemical Engineering, University of Massachusetts, Amherst MA, 01003, U.S.A. ABSTRACT A theoretical analysis based on self-consistent dynamical simulations is presented of electromigration- and stress-induced surface morphological response of voids confined in metallic thin films. The analysis predicts the onset of stable time-periodic states for the void surface morphological response, which is associated with current-driven wave propagation on the void surface. This time-periodic response is demonstrated under certain electromigration conditions and detailed response diagrams are presented which map the corresponding parameter space to regions of steady, time-periodic, and unstable surface morphological response. The evolution of the electrical resistance of these thin films also is computed, providing an interpretation for experimentally observed time-periodic response of the electrical resistance of metallic interconnect lines on the basis of current-driven void morphological evolution. In addition, we demonstrate significant effects on the electromigration-induced morphologically stable void migration of mechanical stress application in a metallic thin film. Specifically, we find that under certain electromechanical conditions, elastic stress can cause substantial retardation of void motion, as measured by the constant speed of electromigration-induced translation of morphologically stable voids. More importantly, this effect suggests the possibility for complete inhibition of void motion under stress. INTRODUCTION Electromigration-induced dynamics of voids confined in metallic thin films has been a problem of major interest both for fundamental understanding of driven mass transport and microstructural evolution in solids [1-3] and for addressing important interconnect reliability concerns in integrated circuits [2-4]. Recently, numerous theoretical studies of current-driven void morphological evolution in metallic films have contributed significantly to our understanding of void morphological instability phenomena and their implications for electromigration-induced failure [5-12]. An intriguing electromigration-induced dynamical phenomenon on metal surfaces that has been predicted theoretically is the formation and propagation of various surface wave patterns. These range from current-induced solitary waves and nonlinear surface wave trains propagating on an infinite metal surface in the direction of the electric field [13] to soliton-like features that travel on large-size void surfaces preceding the failure of the metallic film [7], to stable wave propagation on smaller-size void surfaces in films driven by a stronger than critical electric field [8]. In this paper, we present a detailed parametric analysis of time-periodic surface morphological response of voids confined in metallic thin films and analyze the implicatio
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