High-K Dielectric Grid for Backside Illuminated Image Sensors
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Solution Overview
Problem
As backside illuminated image sensor (BIS) devices continue to scale down, existing fabrication methods fail to adequately improve quantum efficiency and reduce destructive interference, limiting their performance.
Innovation Solution
A high-k dielectric grid is formed over the substrate with a high-k dielectric trench and sidewalls, combined with color filters and microlenses, to enhance light detection efficiency and reduce crosstalk between light sensing regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device scaling is continued to reduce geometry size, then fabrication costs are reduced and integration density is increased, but quantum efficiency deteriorates and destructive interference increases
Solution Approach 1:
The patent divides the pixel structure into multiple segments by introducing a grid structure with trenches that separate adjacent photodetectors. This segmentation prevents light from one pixel from interfering with adjacent pixels, thereby reducing destructive interference and improving quantum efficiency while maintaining high integration density through compact pixel array arrangement.
Solution Approach 2:
The patent applies different properties to different regions of the pixel array by introducing localized grid structures with specific trench depths, spacing, and filling materials (such as silicon nitride or oxygen-rich silicon oxide) in specific regions. This allows optimization of light isolation and quantum efficiency in different areas of the sensor based on local requirements.
2Productivity
If device scaling is continued to reduce geometry size, then fabrication costs are reduced and integration density is increased, but destructive interference increases
Solution Approach 1:
The grid structure with trenches physically segments the pixel array, creating isolation barriers between adjacent photodetectors. This segmentation blocks stray light and prevents it from reaching neighboring pixels, thereby eliminating the harmful destructive interference effect while allowing continued scaling for high integration density.
Solution Approach 2:
The patent introduces intermediary materials (such as silicon nitride or oxygen-rich silicon oxide) filled into the grid trenches to act as mediators that absorb or reflect stray light. These intermediary materials prevent harmful light from propagating between pixels, reducing destructive interference while maintaining the compact scaled-down structure.
3Ease of manufacture
If conventional structures are used in scaled devices, then manufacturing is simpler, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent merges the grid structure formation with existing CMOS fabrication processes by integrating trench formation, dielectric filling, and planarization steps into the standard manufacturing flow. This combining approach maintains ease of manufacture using conventional equipment and processes while significantly improving signal-to-noise ratio through effective light isolation and reduced crosstalk.
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 high-k dielectric grid structure improves signal-to-noise ratio and quantum efficiency by maximizing light transmission to the sensor elements while minimizing interference, leading to better performance in image sensing applications.
Implementation Method 1
reduced destructive interference
Implementation Method 2
maximizing light transmission to the sensor elements
Implementation Method 3
color filters
Implementation Method 4
microlenses
Data Source
AI summary
The present disclosure provides an image sensor device and a method for manufacturing the image sensor device. An exemplary image sensor device includes a substrate having a front surface and a back surface, a plurality of sensor elements disposed at the front surface of the substrate. Each of the plurality of sensor elements is operable to sense radiation projected towards the back surface of the substrate. The image sensor also includes a high-k dielectric grid disposed over the back surface of the substrate. The high-k dielectric grid has a high-k dielectric trench and sidewalls. The image sensor also includes a color filter and a microlens disposed over the high-k dielectric grid.