Monolithic LED Micro-Display on Active Matrix Panel
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Solution Overview
Problem
Conventional LED arrays face limitations in size, resolution, and light efficiency due to the loading effect, low field effect mobility of thin film transistors, and incompatibility with CMOS processes, resulting in poor illumination uniformity and limited scalability for large-scale full-color displays.
Innovation Solution
A monolithic LED micro-display panel is manufactured on an Active Matrix panel using flip-chip technology with a two-transistor-one-capacitor (2T1C) structure, allowing independent control of each LED pixel and improved heat dissipation, enabling larger and higher-resolution displays with enhanced light efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive address schemes are used for LED arrays, then manufacturing is simplified, but resolution and individual pixel control are limited
Solution Approach 1:
The patent divides the LED array into individually addressable pixels by implementing active matrix control with separate row and column driver circuits. Each pixel is segmented with its own switching transistor and storage capacitor, enabling independent control while maintaining manufacturability through standardized cell structures.
Solution Approach 2:
The patent transitions from passive row-column scanning to active matrix control by adding a temporal dimension through frame buffering. Each pixel's state is maintained in storage capacitors during the display refresh cycle, enabling precise individual control without increasing spatial complexity.
2Device complexity
If bottom-emitting configuration is used, then circuitry area is reduced, but aperture and light efficiency are limited
Solution Approach 1:
The patent inverts the conventional bottom-emitting architecture to a top-emitting configuration. The LED active region is positioned at the top surface of the substrate, allowing light to emit upward through a larger aperture area, thereby improving light efficiency while the circuitry is routed along the edges and背面 of the substrate.
3Ease of manufacture
If a-Si TFT or poly-Si TFT is used for driver circuitry, then manufacturing is easier, but field effect mobility is too low to provide sufficient current
Solution Approach 1:
The patent changes the material parameter of the TFT from amorphous silicon or poly-silicon to low-temperature crystalline silicon (LTS). This material transition provides significantly higher field effect mobility (exceeding 100 cm²/Vs) while maintaining compatibility with low-temperature processing, enabling sufficient current delivery to LED pixels.
4Device complexity
If LED process is integrated with CMOS process, then monolithic integration is achieved, but thermal compatibility issues arise
Solution Approach 1:
The patent segments the fabrication process into distinct low-temperature LED growth stages and low-temperature CMOS integration stages. The LED structures are grown on separate substrates at controlled temperatures, then transferred and integrated with the CMOS driver circuitry, avoiding thermal incompatibility while achieving monolithic integration.
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
The solution achieves improved forward voltage uniformity, increased yield, and scalability to larger displays with high resolution and efficient heat management, overcoming previous limitations in size and color accuracy.
Implementation Method 1
a light emitting layer, which uses a semiconductor as a light emitting layer
Implementation Method 2
a phosphor which is excited by the light emitted by the light emitting layer and emitted light with wavelength varied from the excitation light
Data Source
AI summary
A high-resolution, Active Matrix (AM) programmed monolithic Light Emitting Diode (LED) micro-array is fabricated using flip-chip technology. The fabrication process includes fabrications of an LED micro-array and an AM panel, and combining the resulting LED micro-array and AM panel using the flip-chip technology. The LED micro-array is grown and fabricated on a sapphire substrate and the AM panel can be fabricated using PMOS process, NMOS process, or CMOS process. LED pixels in a same row share a common N-bus line that is connected to the ground of AM panel while p-electrodes of the LED pixels are electrically separated such that each p-electrode is independently connected to an output of drive circuits mounted on the AM panel. The LED micro-array is flip-chip bonded to the AM panel so that the AM panel controls the LED pixels individually and the LED pixels exhibit excellent emission uniformity. According to this constitution, incompatibility between the LED process and the PMOS/NMOS/CMOS process can be eliminated.