Method for manufacturing thin film transistor (TFT) and OLED display having TFTS manufactured by the same
View Patent ↗An organic light emitting diode (OLED) display and thin film transistor (TFT) manufacturing method thereof are disclosed. According to the present invention, poly-silicon layers for forming active areas of non-driving TFT (e.g. peripheral circuit TFT and switch TFT) and driving TFT used in the OLED display are respectively made by using standard laser crystallization method and non-laser crystallization method or low energy laser crystallization method. Therefore, the peripheral circuit TFT has excellent electrical performance such as high carrier mobility, while the OLED-driving TFT has good stability so that the resultant display can operate with improved luminance uniformity.
1. An organic light emitting diode (OLED) display, having a peripheral circuit and a display area, said display area including a plurality of sub-pixels, each sub-pixel having a light emitting element, said OLED display comprising:
a substrate having a first region and a second region;
first thin film transistors (TFTs) formed on said first region of said substrate, each first TFT comprising a first buffer layer formed on said substrate, an active area formed by a first poly-silicon layer provided on said first buffer layer, a first gate insulation layer covering said active region and a first gate provided on said first gate insulation layer; and
a second TFT formed on said second region of said substrate, said second TFT comprising a second buffer layer formed on said substrate, an active area formed by a second poly-silicon layer provided on said second buffer layer, a second gate insulation layer covering said active area and a second gate provided on said second gate insulation layer,
wherein said first poly-silicon layer and said second poly-silicon layer have different grain properties, and said first gate insulation layer and said second gate insulation layer have different thicknesses.
2. The OLED display of claim 1 , wherein said first TFTs comprise peripheral circuit TFTs used in said peripheral circuit and a switch TFT for switching a state of said sub-pixel, while said second TFT comprises a driving TFT for driving said light emitting element.
3. The OLED display of claim 2 , wherein said first poly-silicon layer and said second poly-silicon layer have different grain structures.
4. The OLED display of claim 3 , wherein said first poly-silicon layer has a column texture in which a grain arrangement thereof is more regular, while said second poly-silicon layer has a texture in which a grain arrangement thereof is irregular and has branch-like veins.
5. The OLED display of claim 4 , wherein said first poly-silicon layer and said second poly-silicon layer have different grain sizes.
6. The OLED display of claim 5 , wherein said first poly-silicon layer and second poly-silicon layer have grain sizes differing from each other by a difference no less than 500 angstrom on the average.
7. The OLED display of claim 2 , wherein a carrier mobility standard deviation of said peripheral circuit TFT is greater than that of said driving TFT.
8. The OLED display of claim 1 , wherein a thickness difference between said first gate insulation layer and said second gate insulation layer is greater than 30 angstrom.
9. The OLED display of claim 1 , wherein said OLED display is a part of an electric device, and said electronic device comprises a power supply coupled with said OLED display for powering said OLED display, and wherein said electronic device is a mobile phone, digital camera, PDA, notebook, desk-top computer, television set, satellite navigation device, vehicle display or portable DVD player.