Multilayer Pixelated Display Bonding for CMOS-LED Integration
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Solution Overview
Problem
Current LCD-TFT and OLED-TFT pixelated displays face issues such as large circuit areas, poor power efficiency, slow refresh rates, and limited luminance due to non-uniformity and high current leakage, which restrict their performance in applications requiring faster refresh rates and higher luminance.
Innovation Solution
A multilayer structure for pixelated displays is formed by bonding a wafer with non-silicon based semiconductor material for LEDs with a silicon-based CMOS wafer using a double-bonding transfer process, allowing for the integration of III-V compound LEDs with Si-CMOS devices on a common silicon platform without through-silicon-vias, thereby avoiding damage to Si-CMOS devices and enabling higher density and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LCD-TFT or OLED-TFT implementations are used, then pixel control is achieved, but circuit area becomes large and power efficiency deteriorates
Solution Approach 1:
The patent merges the LED light source and CMOS driver circuit into a single integrated structure on the same substrate. The CMOS circuit is formed in a first region of the substrate while the LED is formed in a second region, with direct electrical connection between them. This integration eliminates the need for separate driver circuits and intermediate connections, significantly reducing the overall circuit area while maintaining full pixel control functionality.
2Ease of manufacture
If LCD-TFT or OLED-TFT implementations are used, then pixel control is achieved, but power efficiency becomes poor due to high current leakage
Solution Approach 1:
The patent uses homogeneous silicon-based material for both the CMOS driver circuit and the LED structure, ensuring consistent electrical properties throughout the device. This material uniformity reduces interface defects and current leakage paths that occur in heterostructure devices like LCD-TFT or OLED-TFT, leading to significantly improved power efficiency and reduced energy loss.
3Ease of manufacture
If traditional LCD-TFT or OLED-TFT implementations are used, then display function is achieved, but refresh rate is limited to several kHz
Solution Approach 1:
The patent replaces the mechanical/electrical switching mechanism of TFT transistors with direct CMOS control of LED current. The CMOS circuit provides rapid electrical switching capability that directly modulates the LED output, eliminating the bandwidth limitations of TFT-based liquid crystal or organic LED switching. This substitution enables refresh rates exceeding several kHz while maintaining full display functionality.
4Ease of manufacture
If LCD-TFT or OLED-TFT implementations are used, then display operation is achieved, but luminance is low
Solution Approach 1:
The patent incorporates preliminary light generation action by using electroluminescent LED structures that actively generate light rather than merely modulating backlight. The LED is designed with optimized active regions and contact structures that maximize light output efficiency. This preliminary light generation capability, combined with direct CMOS driving, achieves high luminance output while maintaining reliable display operation.
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 results in smaller unit cells, higher array resolution, improved power efficiency, and faster modulation bandwidth, achieving higher luminance and enabling applications like self-emissive projection systems with enhanced refresh rates.
Implementation Method 1
bonding a wafer with non-silicon based semiconductor material for LEDs with a silicon-based CMOS wafer using a double-bonding transfer process
Data Source
Figure 1A~1D
Figure 2A~2B
Figure 2C~2D
AI summary
A method of forming a multilayer structure for a pixelated display and a multilayer structure for a pixelated display is provided. The method comprising providing a first wafer comprising first layers disposed over a first substrate, said first layers comprising non-silicon based semiconductor material for forming p-n junction LEDs (light emitting devices); providing a second partially processed wafer comprising silicon-based CMOS (Complementary Metal Oxide Semiconductor) devices formed in second layers disposed over a second substrate, said CMOS devices for controlling the LEDs; and bonding the first and second wafers to form a composite wafer via a double-bonding transfer process.