Chromium Modified Crystallization of Silicon Thin Films Crystallized by Flash Lamp Annealing

Abstract

Flash lamp annealing (FLA) is a method of quickly crystallizing large areas of amorphous silicon, which is a promising alternative to existing low-throughput laser annealing in the fabrication of low temperature polycrystalline silicon for thin film transistors in display applications [1]. However, FLA tends to promote dewetting of silicon and randomized void formation during melt-phase crystallization [2]. Chromium underlayers have been successfully used [3] to promote silicon adhesion in thicker films, but there are many potential interactions between Cr and Si, such as the formation of silicides and generation of electrical trap states, that may inhibit future transistor performance. The mechanism and effects of these interactions are not yet understood. This work investigates the efficacy of chromium adhesion layers in silicon crystallization by FLA. Various thicknesses and configurations of amorphous silicon, thin chromium, and silicon dioxide barriers were deposited on glass and subjected to FLA. The resulting material was analyzed with electron and atomic-probe microscopy and found to contain a unique repeated pattern of voids, trenches, and SEM-bright spots at the nanometer scale. Energy-dispersive X-ray spectroscopy confirmed the distribution of chromium in crystallized films to be discrete Cr-rich agglomerations 50-70 nm in diameter, with little metallic contamination outside of these isolated areas