Image Sensor Isolation Wall Layout for Optical Crosstalk Control
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Solution Overview
Problem
Existing single point direct time-of-flight measurement devices suffer from strong optical signal crosstalk and poor signal-to-noise ratio due to interference from interconnection layers and increased dark current with larger photosensitive devices.
Innovation Solution
An image sensor is developed with an isolation wall formed in the passivation structural layer, extending between and through adjacent photosensitive devices to the interconnection layer, which suppresses optical crosstalk and improves signal-to-noise ratio by accumulating positive charges near the isolation wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the photosensitive device size is increased to improve detection capability, then the detection area is improved, but the dark current increases and signal-to-noise ratio deteriorates
Solution Approach 1:
The patent divides the photosensitive device into multiple pixel units, each with its own isolation wall. This segmentation allows the total photosensitive area to be increased while maintaining low dark current levels in each individual pixel, thereby preserving signal-to-noise ratio while expanding detection capability.
Solution Approach 2:
The patent introduces isolation walls as intermediary structures between adjacent pixel units. These isolation walls act as mediators that block optical crosstalk and reduce dark current propagation between pixels, enabling larger photosensitive areas without compromising signal-to-noise ratio.
2Strength
If the interconnection layers are added to support larger photosensitive devices, then the structural support is improved, but the optical signal crosstalk increases
Solution Approach 1:
The isolation wall serves as an intermediary structure that blocks optical signals from propagating between adjacent pixel units through the interconnection layers. This mediator structure prevents crosstalk while allowing the interconnection layers to provide necessary structural support for larger photosensitive devices.
Solution Approach 2:
The patent applies local quality by making the isolation wall optically absorbing or reflecting at specific locations between pixels, while maintaining the interconnection layers' structural properties in other areas. This localized treatment prevents crosstalk without compromising overall structural support.
3Object-generated harmful factors
If the isolation wall extends deeper into the array substrate to improve isolation, then the optical crosstalk suppression is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent implements partial action by forming the isolation wall to extend only to a specific depth within the array substrate, rather than through the entire thickness. This partial extension provides sufficient optical isolation to suppress crosstalk while avoiding the manufacturing complexity of forming isolation walls through the complete substrate depth.
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 isolation wall effectively reduces optical crosstalk and dark count rate, enhancing the signal-to-noise ratio while maintaining a simple and cost-effective process.
Implementation Method 1
the isolation wall is between adjacent photosensitive devices and at least passes through the passivation structural layer and extends to the interconnection structural layer
Implementation Method 2
a photosensitive device is in the array substrate
Data Source
AI summary
An image sensor and a formation method of the image sensor are provided in the present disclosure. The method includes forming an array substrate, where a photosensitive device is in the array substrate; forming an interconnection structural layer on the array substrate; forming a passivation structural layer on the interconnection structural layer; and forming a connection pad and an isolation wall in the passivation structural layer. The connection pad is electrically connected to the photosensitive device; and the isolation wall is between adjacent photosensitive devices and at least passes through the passivation structural layer and extends to the interconnection structural layer.