Effect of Crystallographic Structure of Substrate on Texture in Electrodeposited Ni Layers
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1054-FF05-20
Effect of Crystallographic Structure of Substrate on Texture in Electrodeposited Ni Layers Takafumi Shimada, Akinobu Shibata, Chiemi Ishiyama, Masato Sone, and Yakichi Higo Precision and Intelligence Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta Midoriku, Yokohama, 226-8503, Japan ABSTRACT Effect of substrate on the texture of electrodeposited Ni layer was investigated by using various substrates; Ni-P alloy (amorphous), pure Cu (fcc) and pure Ni (fcc). In the case of Ni-P and Cu substrates, deposited Ni layer shows the (115) fiber texture and its formation was not biased by substrate. On the other hand, the formation of texture is not independent of Ni substrate because its texture is not ideal fiber. Near the interface between deposited Ni layer and Ni-P or Cu substrates, fine columnar grains were observed. In contrast, on Ni substrate there are coarse columnar grains ahead of continuous epitaxial region. It is considered that texture of deposited Ni layer is not independent of Ni substrate due to the fact that these columnar grains satisfy a certain orientation relationship with respect to substrate.
INTRODUCTION These days, electrodeposition has become the important technology in fabricating the metallic thin film for microcomponents such as electronic device or micro electro mechanical system device (MEMS device). Since the microstructure of electrodeposited layer can have an influence on the mechanical properties of electrodeposited layer itself as well as the adhesion strength between electrodeposited layer and substrate, it is very important to understand the formation mechanism of electrodeposited layer. In general, substrate consists of regularly spaced steps with terrace planes, which are closed packed planes. Step is monoatomic height and contains monoatomic kink. Since surface energy of step or kink is larger than that of terrace plane, deposited layer nucleate on the step or kink of substrate [1]. Furthermore, deposition phenomena is accompanied by the misfit strain which arises from the difference of lattice constants between deposited layer and substrate. In order to decrease the misfit strain, deposited layer might nucleate satisfying the epitaxial relationship with respect to the substrate [2]. Therefore, it is considered that the effect of substrate is the most important parameter for the formation of electrodeposited layer. It was reported [1, 3] that the initial deposited layer may have the epitaxial relationship with respect to substrate. After reaching a critical thickness, deposited layer becomes highly textured with fine columnar grains and this texture formation is strongly affected by deposition conditions (composition of the electrolyte, current density and temperature, etc.) and not by the substrate [4, 5]. However, the factors or conditions that determine such a critical thickness have not been clarified yet. Therefore, it can be said that there still remain some uncertainties for the effect of substrate on the formation mechanism of electrodeposited layer.
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