AMOLED Pixel Drive Circuit Using Oxide Switch and LTPS Drive Transistors
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Solution Overview
Problem
The existing 2T1C AMOLED pixel driving circuits face issues with high leakage current, low mobility, and reliability problems due to the use of either oxide semiconductor or Poly Silicon thin film transistors, which affect the conversion of voltage signals to current signals.
Innovation Solution
The method involves using an oxide semiconductor thin film transistor as the switch thin film transistor to reduce leakage current and a P type polysilicon thin film transistor, manufactured through Solid Phase Crystallization, as the drive thin film transistor to enhance mobility and reliability, along with a top gate structure to decrease parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If oxide semiconductor thin film transistor is used as switch TFT, then leakage current is reduced, but mobility is lower and reliability is bad
Solution Approach 1:
The invention divides the TFT system into two distinct types: oxide semiconductor TFT for switch function and LTPS TFT for drive function. This segmentation allows each TFT type to be optimized for its specific role, with oxide semiconductor providing low leakage current for switching and LTPS providing high mobility and reliability for driving, thus resolving the contradiction between low leakage current and high reliability
Solution Approach 2:
Different materials are assigned to different functional locations within the pixel circuit. Oxide semiconductor material is used specifically where low leakage current is critical (switch TFT), while LTPS material is used where high mobility and reliability are critical (drive TFT). This local optimization resolves the contradiction by matching material properties to functional requirements
2Speed
If LTPS thin film transistor based on ELA technology is used, then mobility is high, but equality is poor and leakage current is higher
Solution Approach 1:
The invention segments the TFT functions by using LTPS TFT exclusively for the drive function where high mobility is required, and oxide semiconductor TFT for the switch function where low leakage current is required. This functional segmentation resolves the contradiction between high mobility and low leakage current by assigning each material to its optimal application
3Ease of operation
If 2T1C structure is used, then voltage to current conversion is achieved, but parasitic capacitance affects performance
Solution Approach 1:
The invention changes the material parameter of the drive TFT from oxide semiconductor to LTPS, which has inherently lower parasitic capacitance due to its higher mobility and better charge transport characteristics. This parameter change maintains the voltage-to-current conversion function while reducing parasitic capacitance effects, thereby resolving the contradiction
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces leakage current, improves the stability and reliability of the drive thin film transistor, and forms a more stable constant current type OLED element, while minimizing parasitic capacitance, leading to improved performance in AMOLED pixel driving circuits.
Implementation Method 1
performing P type ion doping and rapid thermal annealing to the amorphous silicon layer to crystallize the same into a polysilicon layer
Implementation Method 2
depositing an oxide semiconductor layer on the interlayer insulation layer, and patterning the oxide semiconductor layer to form a switch thin film transistor active layer
Data Source
AI summary
The present invention provides a manufacture method of an AMOLED pixel driving circuit. The method utilizes the oxide semiconductor thin film transistor to be the switch thin film transistor of the AMOLED pixel driving circuit to reduce the leakage current of the switch thin film transistor, and the P type polysilicon thin film transistor manufactured by utilizing the Solid Phase Crystallization is employed to be the drive thin film transistor of the AMOLED pixel driving circuit to promote the mobility, the equality and the reliability of the drive thin film transistor, and utilizing the P type thin film transistor to be the drive thin film transistor can form the constant current type OLED element, which is more stable than the source follower type OLED formed by the N type thin film transistor, and meanwhile, the parasitic capacitance is decreased with the top gate structure.