Modeling self-annealing kinetics in electroplated Cu thin films

Abstract

Electroplated Cu films exhibit a microstructure evolution at room temperature, called self-annealing. The kinetics of this recrystallization process is strongly influenced by plating conditions in the form of Cu film thickness, current density, and additive content in the electrolyte. Existing models have been used and improved to describe the kinetics of self-annealing. This gives the possibility to evaluate the influence of processing parameters and predict self-annealing behavior of electroplated Cu thin films.

Recrystallization of Electrodeposited Copper Thin Films During Annealing

“…Self-annealing (or annealing) in Cu films can also be described using the JMAK model, 7,17 where the fraction recrystallized f is related to the time t after deposition by…”

“…From transmission electron microscopy (TEM) observations, self-annealing was found to be driven by stored energy in the form of dislocations and can thus be described as recrystallization. 6,7 Organic additives in the deposition bath, including suppressors, accelerators, and levelers, were found to play a crucial role in the bottom-up superfilling of Cu in trenches and vias, and were found to be necessary for self-annealing to occur. 8,9 In addition, several other process parameters, including film thickness and plating current density, were found to affect the kinetics of selfannealing.…”

“…Recently, a phenomenological model was developed to describe the effect of additive concentration and plating current density on self-annealing kinetics. 7 However, a model to predict the recrystallization rate and, as a consequence, the resistivity change of interconnects during and after the heat treatment stage is still lacking, despite its industrial significance. In this paper, the annealing of electrodeposited copper thin films is studied using resistivity measurements during isothermal and nonisothermal heating/cooling treatments.…”

Characterization of room temperature recrystallization kinetics in electroplated copper thin films with concurrent x-ray diffraction and electrical resistivity measurements

“…The most commonly used models for resistivity analysis of thin films utilize a combination of the Fuchs surface dominated electron scatter and Mayadas-Shatzkes (MS) grain boundary dominated electron scatter models. 20,21,[26][27][28][29] The Fuchs model assumes that background electron scattering in thin films can be described by a relaxation time, s, as in bulk materials (due to lattice imperfections and phonon scattering), but that the external surfaces of the film provide boundary conditions to the bulk electron scattering mechanism. This model is intended specifically for film thicknesses on the order of the bulk mean free path, k mfp , which is approximately 39 nm in Cu.…”

“…This formalism is often employed in the literature to model the reverse-sigmoidal shaped decay in film resistivity during recrystallization. 26,33 For this purpose, the fraction recrystallized at any given time, s, during the recrystallization process, s 0 s s 1 , is defined in terms of the normalized resistivity drop f q ðsÞ ¼ qðs 0 Þ À qðsÞ qðs 0 Þ À qðs 1 Þ :…”