Back Side Illuminated Image Sensor Deep Trench Isolation
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Solution Overview
Problem
Traditional back side illuminated (BSI) image sensor devices require two types of isolation structures (trench isolation and metal grid) to reduce cross-talk, leading to complex and costly fabrication processes and potential misalignment issues that can degrade performance.
Innovation Solution
The use of deep trench isolation structures formed from the back side of the image sensor device, which replace both trench isolation and metal grid, providing continuous light-reflective isolation between pixels and eliminating the need for alignment between separate structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If two types of isolation structures (trench isolation and metal grid) are used to reduce cross-talk, then cross-talk reduction is improved, but device complexity and fabrication process complexity increase
Solution Approach 1:
The patent combines trench isolation and metal grid into a single integrated isolation structure. The deep trench is filled with reflective material (such as aluminum or silver) that provides both the physical isolation barrier and the light-reflective properties previously requiring separate structures. This merging eliminates the need for two distinct isolation components and their associated alignment procedures.
Solution Approach 2:
The isolation structure performs multiple functions simultaneously: it provides physical separation between pixels, reflects stray light away from adjacent pixels, and serves as an electrical isolation barrier. By consolidating these functions into a single structure formed from the back side, the patent eliminates the need for separate trench isolation and metal grid layers that would each perform subsets of these functions.
2Object-affected harmful factors
If two types of isolation structures are used, then cross-talk reduction is improved, but fabrication cost increases
Solution Approach 1:
The patent combines trench isolation and metal grid into a single integrated isolation structure. The deep trench is filled with reflective material (such as aluminum or silver) that provides both the physical isolation barrier and the light-reflective properties previously requiring separate structures. This merging eliminates the need for two distinct isolation components and their associated alignment procedures.
Solution Approach 2:
The back-side formation of the reflective isolation structure allows it to be self-aligned with the pixel array without requiring additional alignment steps. The structure automatically positions itself relative to the pixels during the back-side processing sequence, eliminating the need for complex alignment equipment and procedures that would increase fabrication costs.
3Object-affected harmful factors
If two types of isolation structures are used, then cross-talk reduction is improved, but manufacturing precision requirements increase due to alignment needs
Solution Approach 1:
The patent combines trench isolation and metal grid into a single integrated isolation structure. The deep trench is filled with reflective material (such as aluminum or silver) that provides both the physical isolation barrier and the light-reflective properties previously requiring separate structures. This merging eliminates the need for two distinct isolation components and their associated alignment procedures.
Solution Approach 2:
The isolation structure is formed during the back-side processing sequence before final assembly, establishing its position relative to the pixel array in advance. This preliminary formation ensures automatic alignment without requiring subsequent alignment steps, as the structure is already positioned correctly when the front side is attached to the back side.
4Object-affected harmful factors
If traditional trench isolation and metal grid are used, then isolation between pixels is provided, but fabrication process time increases
Solution Approach 1:
The patent combines trench isolation and metal grid into a single integrated isolation structure. The deep trench is filled with reflective material (such as aluminum or silver) that provides both the physical isolation barrier and the light-reflective properties previously requiring separate structures. This merging eliminates the need for two distinct isolation components and their associated alignment procedures.
Solution Approach 2:
The isolation structure formation is integrated into the continuous back-side processing flow, maintaining productive action throughout the fabrication sequence. By forming the reflective isolation structure during back-side processing rather than as a separate subsequent step, the patent eliminates idle time and maintains continuous manufacturing operations.
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 approach simplifies the fabrication process, reduces costs, and enhances image sensor performance by minimizing cross-talk and improving color shading uniformity, while ensuring accurate alignment and efficient light isolation.
Implementation Method 1
deep trench isolation structures formed from the back side of the image sensor device, which replace both trench isolation and metal grid, providing continuous light-reflective isolation between pixels
Data Source
AI summary
A semiconductor image sensor includes a substrate having a first side and a second side that is opposite the first side. An interconnect structure is disposed over the first side of the substrate. A plurality of radiation-sensing regions is located in the substrate. The radiation-sensing regions are configured to sense radiation that enters the substrate from the second side. A plurality of isolation structures are each disposed between two respective radiation-sensing regions. The isolation structures protrude out of the second side of the substrate.