Multi-Layer Alignment Mark Contrast for COG Display Mounting
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Solution Overview
Problem
In Chip-on-Glass (COG) display devices, the low contrast between alignment mark shapes on the IC chip makes it difficult to accurately detect and align the semiconductor device with the transparent substrate, hindering precise mounting.
Innovation Solution
The alignment marks on the IC chip are formed using distinct patterns in different layers, with a first pattern that scatters light and a second pattern that reflects light, increasing the contrast ratio to improve detectability by a photodetector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alignment marks are formed by etching one layer with contrasting shapes, then the alignment mark can be formed on the IC chip, but the contrast between bright and dark regions is low making detection difficult
Solution Approach 1:
The patent transitions from a single-layer alignment mark to a multi-layer structure. The first pattern is formed in a lower layer (first insulating layer) while the second pattern is formed in an upper layer (second insulating layer), creating vertical separation. This dimensional change allows light to interact with different patterns at different depths, significantly enhancing the contrast between bright and dark regions for photodetector detection.
Solution Approach 2:
The alignment mark is segmented into two distinct patterns formed in separate layers. The first pattern (scatter pattern) in the lower layer and the second pattern (reflection pattern) in the upper layer are spatially separated vertically. This segmentation allows each pattern to perform its specific optical function independently, with the lower layer scattering light to create dark regions and the upper layer reflecting light to create bright regions, thereby improving overall contrast.
2Ease of manufacture
If the first pattern and second pattern are formed by the same layer, then the alignment mark structure is simple, but the contrast ratio is low reducing detectability
Solution Approach 1:
Instead of using a single layer, the patent utilizes multiple layers stacked vertically. The first pattern is formed in the first insulating layer while the second pattern is formed in the second insulating layer above it. This vertical dimensionality allows both patterns to coexist without interfering with each other's optical functions, enabling high contrast while maintaining manufacturability through standard multi-layer semiconductor fabrication processes.
Solution Approach 2:
The alignment mark structure becomes a composite of multiple insulating layers, each containing specific patterns. The first insulating layer contains the scatter pattern while the second insulating layer contains the reflection pattern. This composite structure combines the optical properties of different layers to achieve superior contrast performance compared to a single-layer approach.
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 solution enhances the visibility and accuracy of alignment marks, allowing for precise alignment and mounting of the IC chip on the transparent substrate, improving the overall alignment process in COG display devices.
Implementation Method 1
a first shape that scatters incident light from the photodetector
Implementation Method 2
a second shape that efficiently reflects the incident light in an incident direction
Data Source
AI summary
An exemplary display device includes a transparent substrate and a semiconductor device bonded to the transparent substrate. The transparent substrate includes a first alignment mark. The semiconductor device includes a substrate and a second alignment mark positioned on the substrate. The second alignment mark includes a first pattern structure positioned on the substrate and a second pattern structure positioned on the first pattern structure. The first pattern structure includes a plurality of first non-transparent marks. The second pattern structure includes a second pattern surrounded by the first non-transparent marks. The second pattern is an alignable shape that corresponds to a shape of the first alignment mark on the transparent substrate.