Influence of Plasma Surface Treatment of Polyimide on the Microstructure of Aluminum Thin Films

Eiichi Kondoh

doi:10.3390/coatings12030334

Abstract

The effects of plasma treatment of polyimide substrates on the texture and grain size distribution of aluminum thin films were studied. Oxygen-argon plasma treatment increased the average grain size and enhanced the (111) film texture. For short oxygen-argon plasma treatment times, the deposited Al films showed a (111) texture with a bimodal grain structure and even a {111}<112¯> type in-plane texture. The preferential nucleation and grain growth of (111) grains are discussed in terms of the interface energy anisotropy.

Highlights

Microstructure strongly influences the mechanical, electrical, and metallurgical properties of polycrystalline metal thin films
Most studies on grain growth in thin films on amorphous substrates have assumed that the interface energy is identical to the surface energy
The (111) texture of Al films deposited on plasma-pretreated substrates stems from the anisotropy of the Al-polyimide interface energy

Summary

Introduction

Microstructure strongly influences the mechanical, electrical, and metallurgical properties of polycrystalline metal thin films. This correlation has received much attention in pure Al and Al alloys because of the importance of the reliability of these materials in microelectronics, where they are used as electrical conductors [1–10]. When a crystalline film grows on a crystalline substrate and the lattices of the two match, the total periodic potential energy function is minimized so that the film grows epitaxially. Minimization of the film surface energy becomes a primary factor. The (111) texture of Al on thermally grown amorphous SiO2 has been discussed with respect to surface energy minimization [14–16]. Most studies on grain growth in thin films on amorphous substrates have assumed that the interface energy is identical to the surface energy

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