Image Sensor Black Pixel Light Blocking Layer Design
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Solution Overview
Problem
Conventional image sensor devices have increased thickness and differing electrical characteristics between active and optical black pixel regions due to the presence of a top metal layer, which complicates the hydrogen passivation process and affects noise and dark characteristics.
Innovation Solution
The implementation of a light blocking layer, made of amorphous silicon or crystalline silicon, in the optical black pixel region to block light and allow for a hydrogen passivation process, while omitting the top metal layer to ensure uniform metal wire structure and electrical characteristics across regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a top metal layer is formed in the optical black pixel region to block light, then light blocking performance is improved, but the overall thickness of the device increases and electrical characteristics differ from the active pixel region
Solution Approach 1:
The patent removes the top metal layer from the optical black pixel region and replaces it with a light blocking layer made of silicon-based material formed through a different process. This extraction of the problematic metal layer eliminates the thickness increase while maintaining light blocking functionality through the alternative light blocking layer structure.
Solution Approach 2:
The patent changes the material parameter from metal to silicon-based material for the light blocking function. This parameter change allows the light blocking layer to be formed without increasing device thickness significantly, while also enabling compatibility with the hydrogen passivation process used in active pixel regions.
2Object-affected harmful factors
If a top metal layer is formed in the optical black pixel region to block light, then light blocking performance is improved, but electrical characteristics uniformity between active and optical black regions deteriorates
Solution Approach 1:
The patent makes the light blocking layer serve multiple functions: it blocks light in the optical black pixel region while also being compatible with the hydrogen passivation process used in active pixel regions. This universality allows the same fabrication process to be applied to both regions, ensuring uniform electrical characteristics.
Solution Approach 2:
By changing the material parameter from metal to silicon-based material, the patent enables the light blocking layer to undergo hydrogen passivation like the active pixel region structures. This parameter change ensures that both regions experience the same electrical characteristic improvements from the passivation process.
3Reliability
If hydrogen passivation process is applied to improve electrical characteristics in active pixel region, then electrical characteristics are improved, but the process cannot be applied to optical black pixel region with top metal layer
Solution Approach 1:
The silicon-based light blocking layer is designed to be compatible with the hydrogen passivation process, allowing the same process to be uniformly applied across both active and optical black pixel regions. This universality improves electrical characteristics in both regions simultaneously.
4Device complexity
If filters of single color are used in optical black pixel region, then manufacturing complexity is reduced, but light blocking effectiveness must be compensated
Solution Approach 1:
The patent uses a composite structure combining a single-color filter layer with a silicon-based light blocking layer. This composite approach simplifies the filter arrangement while the silicon layer provides additional light blocking effectiveness, compensating for the reduced filter complexity.
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 reduces the overall thickness of the image sensor device, enhances pixel sensitivity, and uniformity of electrical characteristics, such as noise and dark performance, by allowing similar metal wire structures and hydrogen passivation processes in both active and optical black pixel regions.
Implementation Method 1
a light blocking layer 138 in the optical black pixel region between the filter unit and the light receiving unit... configured to block light that has passed through the filter unit
Implementation Method 2
an annealing process, such as a hydrogen passivation process, is generally performed after the pixel metal wire layer 120 is formed
Data Source
AI summary
An image sensor device includes an optical black pixel region and an active pixel region. The image sensor device includes a light receiving unit including a plurality of light sensitive semiconductor devices that are configured to detect light incident thereon, a pixel metal wire layer including a transparent material on the light receiving unit and including a plurality of metal wires therein, and a filter unit on the pixel metal wire layer. The filter unit includes a plurality of filters that are configured to transmit light according to a wavelength thereof. The filters of the filter unit in the optical black pixel region of the image sensor device have a single color. The image sensor device further includes a light blocking layer in the optical black pixel region between the filter unit and the light receiving unit. The light blocking layer is configured to block light that passes through the filter unit.