Chemical Vapor Deposition

Chemical Vapor Deposition (CVD) is used by flat panel display (FPD) manufacturers to deposit most of the layers, commonly called ^“films,^” which function as dielectrics (insulators) or semiconductors (partial conductors).

During CVD processing, gases that contain the constituent atoms or molecules of the material to be deposited are introduced into the controlled environment of the process chamber. The reactive gases are dissociated in an RF Plasma to form reactive radicals or ions, which undergo chemical reactions for thin film on the heated substrate.

There are several kinds of CVD films. The most common in use for thin film transistor - liquid crystal displays (TFT-LCDs) are:

• Silicon dioxide (SiO_x)
• Silicon nitride (SiN_x)
• Amorphous silicon (a-Si)
• Low Temp Polysilicon Pre-cursor

Silicon dioxide and silicon nitride dielectrics act as insulators within the TFT structure and as the passivation layer. Amorphous silicon and polysilicon act as semiconductors partial conductors within the TFT.