Metal-induced crystallization (MIC) is a method by which

amorphous carbon Amorphous carbon is free, reactive carbon that has no crystalline structure. Amorphous carbon materials may be stabilized by terminating dangling-π bonds with hydrogen. As with other amorphous solids, some short-range order can be observed. Amorp ...

(a-C),

amorphous silicon Amorphous silicon (a-Si) is the non- crystalline form of silicon used for solar cells and thin-film transistors in LCDs. Used as semiconductor material for a-Si solar cells, or thin-film silicon solar cells, it is deposited in thin films ...

(a-Si), amorphous oxides and amorphous germanium (a-Ge) can be turned into their

polycrystalline A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. Crystallites are also referred to as grains. Bacillite is a type of crystallite. It is rodlike with parallel longulites. Stru ...

phases at relatively low

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied on ...

s. In the technologically important case of Si, a thin film of a-Si is deposited onto a substrate, usually

glass Glass is a non-Crystallinity, crystalline, often transparency and translucency, transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most ...

, and then capped with a

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typi ...

, such as

aluminium Aluminium (aluminum in AmE, American and CanE, Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately o ...

(Aluminum-induced crystallization(AIC)). The structure is then annealed at temperatures between 150

°C The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The d ...

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 A thin-film transistor (TFT) is a special type of field-effect transistor (FET) where the transistor is thin relative to the plane of the device. TFTs are grown on a supporting (but non-conducting) substrate. A common substrate is glass, because ...

. 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. Recently metal-induced crystallization has been coupled with microwave-assisted crystallization lowering the crystallization temperature and time of amorphous titania. By suspending the amorphous powder in a salty solution containing one of various d-block or p-block elements, and microwaving, crystallization can be induced within a few minutes.

References

{{DEFAULTSORT:Metal-Induced Crystallization Semiconductor device fabrication Inorganic chemistry Chemical processes Crystallography