Buried Grid Optical Structure for Image Sensor Crosstalk Isolation
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Solution Overview
Problem
Image sensors face challenges with crosstalk between adjacent light detection regions, which degrades performance and reduces quantum efficiency due to the presence of metallic structures that block photons, especially as sensors become smaller.
Innovation Solution
A buried grid structure is introduced to provide optical isolation between adjacent light detection regions, comprising a metal nitride and metallic section within a dielectric layer, which helps block light and reduce crosstalk while maintaining quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If metallic structures are used to block light between pixels, then crosstalk is reduced, but quantum efficiency decreases due to photon blocking
Solution Approach 1:
The patent extracts the light-blocking function from traditional metallic grid structures and relocates it to a dielectric layer positioned between the pixel regions. This removes the harmful metallic structures that blocked photons while preserving the necessary optical isolation function, thereby reducing crosstalk without sacrificing quantum efficiency.
Solution Approach 2:
The patent introduces a dielectric layer as an intermediary substance between adjacent pixel regions to provide optical isolation. This dielectric mediator blocks light propagation between pixels without the photon-absorbing properties of metals, achieving crosstalk reduction while maintaining high quantum efficiency.
2Device complexity
If sensor size is reduced to improve integration, then device complexity decreases, but crosstalk between adjacent pixels increases
Solution Approach 1:
The patent addresses the crosstalk problem by moving from a two-dimensional planar isolation approach to a three-dimensional solution, inserting a dielectric layer vertically between pixel regions. This dimensional transition enables effective optical isolation in compact sensor designs where lateral spacing is limited.
Solution Approach 2:
The patent extracts the light-blocking function from the pixel structure itself and places it in a dedicated dielectric isolation layer, enabling smaller pixel pitch without increasing crosstalk.
3Ease of manufacture
If traditional metallic grid structures are used for optical isolation, then manufacturing is well-established, but quantum efficiency is reduced due to metal photon blocking
Solution Approach 1:
The patent changes the material parameter from metallic to dielectric, fundamentally altering the optical interaction from photon absorption (metal) to photon transmission with spatial isolation (dielectric). This parameter change enables compatibility with existing CMOS fabrication processes while eliminating the quantum efficiency penalty of metallic grids.
Solution Approach 2:
The patent replaces expensive and photon-blocking metallic grid structures with inexpensive dielectric materials that can be deposited using standard semiconductor manufacturing techniques, achieving both cost reduction and performance improvement.
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 buried grid structure effectively reduces crosstalk and improves quantum efficiency by blocking light between neighboring pixels without significantly sacrificing performance, and can be easily integrated into existing image-sensing devices.
Implementation Method 1
The buried grid structure laterally arranged around and between the image-sensing elements provides optical isolation between neighboring light detection regions
Data Source
AI summary
An optical structure and methods of forming an optical structure are provided. In some embodiments, the optical structure includes a substrate having a frontside and a backside opposite the frontside, a plurality of image-sensing elements arranged within the substrate, and a deep trench isolation (DTI) structure disposed between adjacent image-sensing elements. The DTI structure extends from the backside of the substrate to a first depth within the substrate and laterally surrounds the plurality of image-sensing elements. The optical structure further includes a light transmission layer formed over the backside of the substrate. The light transmission layer includes a first side and a second side adjacent to the backside of the substrate. The optical structure further includes a buried grid structure in the light transmission layer, the buried grid structure extending from the first side of the light transmission layer to a second depth within the light transmission layer.