Laser Annealing for Display Panels

Principles of Liquid Crystal Display

 

A liquid crystal display is a collection of pixels arranged vertically and horizontally to create a single image. Images become a movie by rewriting the images many times per second. Image rewriting is performed by repeatedly turning on and off the TFTs in the sub-pixels.

  • The faster the speed at which the TFTs are switched, the faster the video that can be supported.
  • The smaller in size and larger quantity of pixels, the higher the resolution of the image will be.

 

Effects of Laser Annealing

 

A property of amorphous silicon (a-Si), which is conventionally used for pixel-driving TFTs, is that it is a poor conductor of electricity. However, when a-Si is annealed by laser irradiation, the silicon melts and recrystallizes (polycrystal), and thereby forming poly-silicon (p-Si), which is a good conductor of electricity. This means that laser annealing can improve the electrical characteristics of the TFTs. In the past, a-Si was heated to a high temperature in a furnace to form p-Si, but there were other problems other than TFT such as being affected by heat and the time required for heating. Laser annealing solves the problems associated with high temperature heating in a furnace because the irradiated parts can be heated and cooled rapidly.

 

Features of Laser Annealing Method

 

As the size of TV screens increases, the size of mass-produced display substrates also increases. In conventional laser annealing methods, the size of display substrates that can be annealed is limited due to lens size limitations. Gigaphoton is co-developing with an annealing equipment manufacturer with the aim of achieving annealing technology for which there is no limit for the display size.