Active matrix display devices and the manufacture thereof
View Patent ↗An active plate ( 2 ) for an active matrix display device ( 16 ), the active plate ( 2 ) comprising a substrate ( 4 ), a pixel area ( 6 ) and an adjacent drive circuit area ( 8 ). Both areas include polycrystalline silicon material formed by a process in which a metal is used to enhance the crystallization process (MIC poly-Si), but only the MIC poly-Si in the drive circuit area ( 8 ) is subjected to an irradiation process using an energy beam ( 10 ). TFTs are fabricated with MIC poly-Si which have leakage currents in the off state sufficiently low for them to be acceptable for use as switching elements in the pixel area of matrix display devices. As only the drive circuit area ( 8 ) need be irradiated to provide poly-Si having the desired mobility, the time taken by the irradiation process can be significantly reduced.
1. An active plate for an active matrix display device, the active plate comprising
a substrate, a pixel area and an adjacent drive circuit area, each of the pixel area and the drive circuit area including MIC poly-Si, the drive circuit area comprising a digital circuitry region and an analogue circuitry region, each of the digital circuitry region and the analogue circuitry region including MIC poly-Si, with only MIC poly-Si in the digital circuitry region of the drive circuit area having been subject to an annealing process using an energy beam.
2. The active plate of claim 1 , wherein substantially all the MIC poly-Si of the drive circuit area is located to one side of the pixel area.
3. The active plate of claim 1 , wherein the MIC poly-Si includes nickel at a concentration in the range of 1.3×10 18 to 7.5×10 18 atoms/cm 3 .
4. The active plate of claim 3 , wherein the MIC poly-Si includes nickel at a concentration around 2.5×10 18 atoms/cm 3 .
5. A method of fabricating an active plate for a matrix display device, the active plate having a pixel area and an adjacent drive circuit area, the method comprising the steps of:
(a) depositing an amorphous silicon film on a substrate;
(b) adding to the pixel area and drive circuit area a metal element for accelerating crystallisation of amorphous silicon;
(c) heating the substrate to crystallise amorphous silicon in the film to form MIC poly-Si; and
(d) irradiating only MIC poly-Si in a digital circuitry region of the drive circuit area with an energy beam.
6. The method of claim 5 , wherein in step (b) the metal element is nickel and it is added to the amorphous silicon film at a concentration in the range 1.3×10 18 to 7.5×10 18 atoms/cm 3 .
7. The method of claim 6 , wherein in step (b) the metal element is nickel and it is added to the amorphous silicon film at a concentration around 2.5×10 18 atoms/cm 3 .