Metal-induced crystallization
Encyclopedia
Metal-induced crystallization (MIC) is a method by which amorphous silicon
, or a-Si, can be turned into polycrystalline silicon
at relatively low temperature
s. 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.
Amorphous silicon
Amorphous silicon is the non-crystalline allotropic form of silicon. It can be deposited in thin films at low temperatures onto a variety of substrates, offering some unique capabilities for a variety of electronics.-Description:...
, or a-Si, can be turned into polycrystalline silicon
Polycrystalline silicon
Polycrystalline silicon, also called polysilicon, is a material consisting of small silicon crystals. It differs from single-crystal silicon, used for electronics and solar cells, and from amorphous silicon, used for thin film devices and solar cells....
at relatively low temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
s. In MIC an amorphous Si film is deposited onto a substrate, usually glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
or Si, and then capped with a metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
, such as aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
. 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.