1. Laser Annealing

What is laser annealing?

Annealing is a process of reforming the surfaces of materials by first heating the surface and then cooling it, methods of heating including those by furnaces or lamps, or laser annealing. Laser annealing, as the words imply, performs annealing using a laser, rapidly heating the surface and allow it to self-cool, and this process can be performed in the open air. The basic equipment structure for laser annealing is a structure that scans the surface of a material on a scanner or stage for focusing a laser beam using a condensing lens.

What is laser annealing for liquid crystal manufacture?

The silicon (Si) film on a liquid crystal panel substrate is irradiated by a laser to heat it at a low temperature and reform it into a poly-silicon (p-Si) liquid crystal.

Why is laser annealing required?

Originally, p-Si was formed by high temperature heating in a furnace. However, this had problems such as the substrate being affected by the heat due to high temperature heating, and the process taking too long. Since low temperature heating by laser annealing heats the surface of the material quickly and allows it to cool down on its own, the problems caused by high temperature heating in a furnace are solved.

What effects does laser annealing have?

The drive section of a transistor is usually formed by an amorphous silicon (a-Si, a noncrystalline semiconductor) layer, driven with the speed of movement of electrons (mobility characteristic) at around 0.5. If the a-Si layer is reformed into a p-Si layer by a LTPS process, high-speed driving at a mobility of 100 and upward is made possible and the layer can correspond to increases in the definition of panels.

What is the difference between the line beam method and the multi-lens array method?

Up until the current Gen8 (glass panel size) generation, line beams have been used to irradiate the front surface of an Si film on a glass substrate to anneal it. In recent years, solid state lasers have also been developed, and development of microscopic annealing using multiple lenses with YAG lasers is proceeding. This is attracting interest as a process that enables energy to be used efficiently due to annealing being performed essentially only inside the transistor.