Metal-induced crystallization

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Metal-induced crystallization (MIC) is a method by which amorphous silicon, or a-Si, can be turned into polycrystalline silicon at relatively low temperatures. In MIC an amorphous Si film is deposited onto a substrate, usually glass or Si, and then capped with a metal, such as aluminium. The structure is then annealed at temperatures between 150 °C and 400 °C which causes the a-Si films to be transformed into polycrystalline silicon.

In a variant of this method, called Metal-induced lateral crystallization (MILC), metal is only deposited on some area of the a-Si. Upon annealing, crystallization starts from the portion of a-Si which is covered by metal and proceeds laterally. Unlike MIC process, where metal contamination in the obtained polysilicon is relatively high, the laterally crystallized silicon in MILC process contains very small amount of metal contamination. The crystallization speed is low, but is adequate for applications such as fabrication of thin film transistors. In this case, metal is deposited on the source/drain area of the transistor and the channel is laterally crystallized.

It has been also shown that applying an electric field increases the speed of lateral crystallization dramatically. Moreover, the crystallization proceeds unidirectionally.