Stacked Image Sensor Isolation Structure for Analog-Digital Crosstalk
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Solution Overview
Problem
The increasing integration density of image sensors leads to significant electric interference between circuit patterns, necessitating a solution to reduce this interference.
Innovation Solution
The implementation of an image sensor design that includes a first substrate with an analog block and a digital block separated by an isolation structure, along with specific transistor configurations and a color filter array layer, and a method of manufacturing that involves forming isolation patterns and bonding substrates to create an effective isolation structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the integration density of the image sensor is increased, then the size is decreased and high integration is achieved, but electric interference between circuit patterns increases
Solution Approach 1:
The image sensor is divided into multiple substrates (first substrate, second substrate, third substrate) with distinct functional blocks. Analog circuits and digital circuits are separated onto different substrates or regions, reducing electric interference while maintaining high integration density. The isolation structure further segments the substrate to prevent signal crosstalk between adjacent circuit patterns.
Solution Approach 2:
An isolation structure comprising insulating materials is introduced between analog and digital circuit patterns to act as an intermediary barrier. This isolation structure includes isolation patterns formed in insulating layers that physically separate and electrically isolate adjacent circuit blocks, thereby reducing harmful electric interference while allowing both circuits to operate at high integration density.
2Object-affected harmful factors
If an isolation structure is introduced to reduce electric interference, then circuit isolation is improved, but device complexity increases
Solution Approach 1:
The isolation structure is merged with the existing multi-layer interconnect architecture of the image sensor. Insulating layers and isolation patterns are integrated into the standard CMOS fabrication process, combining the isolation function with the existing circuit layout rather than adding separate isolation components. This reduces overall device complexity while achieving effective circuit isolation.
Data Source
AI summary
An image sensor includes a first substrate including an analog block and a digital block, an isolation structure extending through the first substrate and dividing the analog block from the digital block, a first transistor on the digital block, a second transistor on the analog block, a wiring on and electrically connected to the second transistor, a second substrate on the wiring, a color filter array layer on the second substrate and including color filters, a microlens on the color filter array layer, a light sensing element in the second substrate, a transfer gate (TG) extending through a lower portion of the second substrate adjacent to the light sensing element, and a floating diffusion (FD) region at a lower portion of the second substrate adjacent to the TG and electrically connected to the wiring.