Stacked Image Sensor Contact Pattern for SNR and Bonding Reliability
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Solution Overview
Problem
Current CMOS image sensors face challenges in enhancing electrical properties and signal-to-noise ratio due to limitations in wiring connections and dielectric layers, leading to inefficiencies in light reception and crosstalk between pixel regions.
Innovation Solution
The proposed image sensor design includes a multi-substrate structure with specific dielectric layers and contact patterns to improve electrical connections, such as a contact pattern with a recess region and a protrusion part, which allows for more efficient electrical connections between bonding pads and wiring layers, reducing the need for deep contact holes and preventing failures in bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep contact holes are used to connect wiring layers across substrates, then electrical connection is achieved, but manufacturing complexity and risk of bonding failure increase
Solution Approach 1:
The patent introduces a contact pattern layer with recess and protrusion structures that extends the connection path horizontally across the substrate interface rather than vertically through deep contact holes. This dimensional transformation allows electrical connection without requiring deep penetrating contacts, thereby reducing bonding complexity and failure risk while maintaining electrical connectivity between wiring layers on different substrates.
2Reliability
If more dielectric layers and wiring layers are added to improve electrical properties, then signal-to-noise ratio improves, but device complexity increases
Solution Approach 1:
The patent divides the electrical connection path into multiple segments across different layers (first wiring layer, second wiring layer, contact pattern layer, third wiring layer) separated by dielectric layers. This segmentation allows each layer to be optimized independently for its specific function while collectively achieving improved signal-to-noise ratio through controlled impedance and isolation, without requiring a single complex deep connection structure.
Solution Approach 2:
The contact pattern layer with recess and protrusion structures serves as an intermediary element between the first and second wiring layers across the substrate interface. This intermediate structure facilitates electrical connection while providing isolation and controlled impedance, thereby improving signal-to-noise ratio without directly adding complex deep contact holes or excessive dielectric layers.
3Area of stationary object
If bonding pads are placed close to connection contacts to reduce spacing, then area is reduced, but electrical connection reliability decreases
Solution Approach 1:
The contact pattern structures incorporate recess and protrusion features that create curved or non-linear connection paths between bonding pads and wiring layers. This curvature allows the electrical connection to maintain adequate spacing and reliability while reducing the overall planar area occupied by the pad structure, as the connection path follows a more space-efficient geometric configuration.
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 design enhances the electrical properties of the image sensor by improving light-receiving efficiency and signal-to-noise ratio, reducing crosstalk, and preventing failures in bonding, thereby increasing the overall performance of the image sensor.
Implementation Method 1
a connection contact configured to penetrate the second substrate and electrically connect the lower wiring line to the first bonding pad
Implementation Method 2
The photodiode serves to convert incident light into electrical signals
Data Source
AI summary
Disclosed is an image sensor comprising a first substrate including unit pixel regions and having first and second surfaces opposite to each other, a second substrate below the first surface of the first substrate, a third substrate below the second substrate, a lower dielectric layer between the second and third substrates, a lower wiring line in the lower dielectric layer, an intermediate dielectric layer between the first and second substrates, a first bonding pad in the intermediate dielectric layer, a connection contact that penetrates the second substrate and electrically connects the lower wiring line to the first bonding pad, and a contact pattern in the intermediate dielectric layer and below the first bonding pad. The first bonding pad is vertically spaced apart from the connection contact by the contact pattern.