Stacked Micro-Display Layout for Smaller Chips and Higher Yield
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Solution Overview
Problem
The existing micro-display technology faces challenges with large chip size, low yield, high cost, and process incompatibility between pixel and drive circuits, limiting performance improvement due to differences in manufacturing processes required for each circuit type.
Innovation Solution
A stacked micro-display structure is developed with a substrate having a pixel circuit on one surface and a drive circuit on the opposite surface, connected by interconnects, using a silicon-on-insulator (SOI) wafer with separate manufacturing processes for each circuit type to reduce chip area and improve yield, and a manufacturing process that includes steps for preparing the substrate, manufacturing layers, and connecting the circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the chip size is increased to accommodate both pixel circuit and peripheral drive circuit on the same substrate, then the integration is achieved, but the yield decreases and cost increases
Solution Approach 1:
The display device is divided into two separate substrates: a first substrate for the pixel circuit and a second substrate for the drive circuit. This segmentation allows each substrate to be optimized independently for its specific function, avoiding the yield penalty of large integrated chips while maintaining full functionality through the stacking architecture.
Solution Approach 2:
The patent transitions from a planar integration approach to a three-dimensional stacked architecture. By stacking the pixel circuit substrate and drive circuit substrate vertically with an encapsulation layer in between, the system achieves integration in the vertical dimension rather than expanding horizontally, thereby maintaining small chip footprint while achieving full functionality.
2Reliability
If different manufacturing processes are used for pixel circuit and drive circuit to meet their specific requirements, then the performance is optimized, but the process integration becomes difficult
Solution Approach 1:
By segmenting the display device into separate substrates for pixel circuits and drive circuits, each substrate can be manufactured using processes optimized for its specific requirements without needing to integrate multiple process nodes on the same wafer. This resolves the process incompatibility issue while maintaining high performance for both circuit types.
Solution Approach 2:
The patent uses transfer printing technology to transfer the pixel circuit array from a fabrication substrate to the display substrate. This copying approach allows the pixel circuits to be manufactured using a different process node than the drive circuit, enabling independent optimization of each circuit type's manufacturing process while achieving integration in the final stacked structure.
3Productivity
If the chip area is reduced to improve yield and reduce cost, then the manufacturing efficiency increases, but the area for peripheral drive circuit is limited
Solution Approach 1:
The patent resolves the area limitation by moving the drive circuit to a separate substrate in the vertical stacking direction. This allows the pixel circuit substrate to maintain a small area optimized for high yield, while the drive circuit occupies space on the second substrate, effectively distributing the area requirements across multiple dimensions rather than competing for the same planar space.
Data Source
AI summary
Disclosed in the present disclosure are a stacked micro-display structure and a manufacturing process therefor. The stacked micro-display structure includes a substrate, where a first surface of the substrate is provided with a pixel circuit, and a second surface, opposite to the first surface, of the substrate is provided with a drive circuit. The manufacturing process includes: step 1) preparing a substrate; step 2) manufacturing a drive circuit layer on a back surface, facing upward, of the substrate; step 3) turning the substrate over, and attaching the drive circuit layer to a carrier; step 4) manufacturing a pixel circuit layer on a front surface of the substrate; step 5) manufacturing via holes; step 6) manufacturing interconnects; step 7) manufacturing an anode electrode; and step 8) manufacturing a light-emitting layer and a cathode; and manufacturing an encapsulation layer.