Dielectric Grid Metal Pillar Image Sensor Cross-Talk
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Solution Overview
Problem
As backside illuminated image sensor (BSI) devices continue to scale down, existing fabrication methods have not been entirely satisfactory in improving quantum efficiency, leading to issues with light interference and cross-talk among light sensing regions.
Innovation Solution
The implementation of a dielectric grid with a metal pillar core and a stack of layers with increasing refractive index, along with an etch-stop-layer and polymer layer, to enhance light transmittance and reduce cross-talk, is proposed. This structure includes a first dielectric layer, a metal pillar as the core, and a second dielectric layer wrapping around it, with a polymer layer between dielectric grids to increase the critical angle of total internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device geometry is scaled down to achieve higher integration density, then device integration density is improved, but light interference and cross-talk among light sensing regions increases
Solution Approach 1:
The patent introduces a dielectric grid structure that divides and segments the light paths reaching the pixel array. The grid comprises alternating light-transmissive and light-reflective regions that spatially separate and direct light from different directions to appropriate sensing regions, preventing cross-talk while maintaining high integration density through scaled-down geometry
Solution Approach 2:
The patent introduces a dielectric grid structure as an intermediary element between the lens array and the pixel array. This grid acts as a mediator that selectively transmits and reflects light based on its position, directing light from different angles to the correct sensing regions and preventing light interference and cross-talk among adjacent pixels
2Ease of manufacture
If device geometry is scaled down to achieve lower fabrication costs, then fabrication cost is reduced, but light interference and cross-talk among light sensing regions increases
Solution Approach 1:
The dielectric grid structure segments light paths using alternating transmissive and reflective regions, enabling effective cross-talk prevention in scaled-down devices without requiring complex or expensive fabrication processes
Solution Approach 2:
The dielectric grid utilizes composite material properties by combining light-transmissive and light-reflective regions within a single structure, achieving multifunctional light management (transmission, reflection, and spatial separation) that effectively reduces cross-talk while maintaining fabrication simplicity
3Device complexity
If existing BSI fabrication methods are used, then manufacturing process is simple, but quantum efficiency improvement is insufficient due to light interference
Solution Approach 1:
The dielectric grid segments incident light into transmitted and reflected components, directing each to appropriate sensing regions. This segmentation approach improves quantum efficiency by ensuring light reaches the correct pixels while maintaining relatively simple fabrication that integrates with existing BSI processes
Solution Approach 2:
The dielectric grid performs multiple functions simultaneously: it acts as a light-transmissive structure, a light-reflective structure, and a spatial separation element all in one component. This multi-functionality improves quantum efficiency through effective light management while adding minimal complexity to the fabrication process
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 improves quantum efficiency by reducing light interference and cross-talk among light sensing regions, enhancing the transmittance rate and overall performance of the image sensor device.
Implementation Method 1
a polymer layer between dielectric grids to increase the critical angle of total internal reflection
Implementation Method 2
a stack of layers with increasing refractive index
Data Source
AI summary
An image sensor device and a method for manufacturing the image sensor device are provided. An image sensor device includes a substrate, sensor elements disposed at a front surface of the substrate, and a dielectric grid disposed over a back surface of the substrate. The dielectric grid includes a first dielectric layer as a bottom portion, a metal pillar, as a core portion of a upper portion, disposed over the first dielectric layer and a second dielectric layer wrapping around the metal pillar. The image sensor device also includes a stack of layers disposed over the back surface of the substrate. Refractive index of each layers increases from top layer to bottom layer. The image sensor device also includes a color filter and a microlens disposed over the back surface of the substrate.