Image Sensor Reflective Grid and Color Filter Trench Design
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Solution Overview
Problem
The challenge in forming reliable semiconductor devices, such as image sensor devices, at increasingly smaller sizes is exacerbated by the complexity and difficulty of fabrication processes as feature sizes decrease, leading to issues with electrical crosstalk and manufacturing yield.
Innovation Solution
The formation of an image sensor device involves a semiconductor substrate with isolation structures and a reflective grid that surrounds light-sensing regions, along with color filters positioned in trenches to reduce optical crosstalk and improve quantum efficiency, while also addressing thermal expansion stress through homojunction contact between color filters, thereby enhancing manufacturing yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes are decreased to increase functional density, then production efficiency is improved and costs are lowered, but fabrication process difficulty increases and manufacturing yield deteriorates
Solution Approach 1:
The patent divides the color filter structure into multiple segments: a first color filter layer and a second color filter layer, with the second layer extending into the trench formed by the reflective grid. This segmentation allows each layer to perform specific functions - the first layer provides color filtering while the second layer extends into the trench to reduce optical crosstalk and prevent delamination, thereby maintaining manufacturing yield despite scaling to smaller feature sizes
Solution Approach 2:
The patent performs preliminary actions by forming the reflective grid structure with trenches before depositing the color filter layers. The trenches are pre-formed to guide the extension of the second color filter layer, which preliminarily establishes the homojunction contact configuration that will prevent delamination during subsequent thermal processing, thus proactively addressing manufacturing yield issues before they occur
2Reliability
If color filters are positioned in trenches to reduce optical crosstalk, then quantum efficiency is improved, but thermal expansion stress may cause delamination between color filters and reflective grid
Solution Approach 1:
The patent uses the same material for both the first color filter layer and the second color filter layer, creating a homojunction between them. This material homogeneity ensures matched thermal expansion coefficients, which prevents delamination caused by thermal expansion stress while maintaining the quantum efficiency benefits of the trench configuration
Solution Approach 2:
The patent creates a composite color filter structure where two layers of the same material (homojunction) are combined, with the second layer extending into the trench. This composite configuration provides both the optical crosstalk reduction needed for high quantum efficiency and the thermal stress management needed to prevent delamination, simultaneously addressing both reliability and strength requirements
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 effectively reduces optical crosstalk and improves quantum efficiency, while preventing delamination between color filters and the reflective grid, resulting in improved yield and reliability of image sensor devices at smaller scales.
Implementation Method 1
a reflective grid over the isolation structure and surrounding the first light-sensing region and the second light-sensing region
Implementation Method 2
A first color filter over the first light-sensing region and extending into the first trench. A second color filter over the second light-sensing region and extending into the first trench
Data Source
AI summary
An image sensor device is provided. The image sensor device includes a semiconductor substrate having a first light-sensing region and a second light-sensing region adjacent to the first light-sensing region. The image sensor device includes an isolation structure in the semiconductor substrate and surrounding the first light-sensing region and the second light-sensing region. The image sensor device includes a reflective grid over the isolation structure and surrounding the first light-sensing region and the second light-sensing region. The image sensor device includes a first color filter over the first light-sensing region and extending into a first trench of the reflective grid. The image sensor device includes a second color filter over the second light-sensing region and extending into the first trench to be in direct contact with the first color filter in the first trench.