Self-aligned Image Sensor Filter Reducing Crosstalk
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Solution Overview
Problem
Conventional image sensors face challenges with low sensitivity due to difficulty in light collection in smaller pixels and crosstalk issues, leading to noise and degraded image reproduction.
Innovation Solution
Self-aligned color filters are placed between metal conductors in the image sensor, extending to the semiconductor substrate, with micro-lenses focusing light onto the filters, which are aligned with photosensitive elements to reduce crosstalk and allow for thicker filters without increasing pixel height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If filters are placed closer to the photosensitive element to reduce crosstalk, then crosstalk reduction is improved, but manufacturing complexity increases due to self-alignment requirements
Solution Approach 1:
The filter structure utilizes the metal conductor patterns already present in the CMOS substrate to define its position and shape. The filter material is deposited to conformally coat the conductor surfaces, automatically aligning with the underlying photosensitive elements through the conductor geometry rather than requiring separate alignment processes.
Solution Approach 2:
The metal conductor patterns are formed first during standard CMOS fabrication, establishing the geometric framework. The filter material is then deposited in a subsequent step, utilizing the pre-formed conductor structures as alignment references, thereby eliminating the need for complex real-time alignment procedures.
2Measurement precision
If pixel size is reduced to increase resolution, then image quality is improved, but light collection capability deteriorates leading to lower sensitivity
Solution Approach 1:
The filter structure extends vertically between metal conductors at different elevation levels within the CMOS stack. This three-dimensional configuration allows the filter to occupy space in the vertical dimension rather than only the horizontal plane, effectively increasing the light collection volume without expanding the pixel footprint.
Solution Approach 2:
The filter structure is nested within the existing CMOS device architecture, utilizing the space between metal conductor layers. The filter material conformally coats the conductor surfaces and fills the inter-conductor regions, effectively nesting the optical function within the electronic structure without adding external components.
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 configuration enhances light collection and reduces crosstalk, improving image sensitivity and quality by ensuring filters are closer to the substrate, thereby minimizing noise and allowing for more efficient light detection.
Implementation Method 1
a micro-lens may be disposed on the filter
Implementation Method 2
micro-lenses focusing light onto the filters
Implementation Method 3
A filter may be disposed between at least two of the plurality metal conductors
Data Source
AI summary
An image sensor includes at least one photosensitive element disposed in a semiconductor substrate. Metal conductors may be disposed on the semiconductor substrate. A filter may be disposed between at least two individual metal conductors and a micro-lens may be disposed on the filter. There may be insulator material disposed between the metal conductors and the semiconductor substrate and/or between individual metal conductors. The insulator material may be removed so that the filter may be disposed on the semiconductor substrate.