Backside Image Sensor Isolation With H-Shaped Etch Stop Layers
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Solution Overview
Problem
The challenge of forming reliable image sensor devices at smaller sizes is exacerbated by the difficulty in fabricating complex circuits with decreasing feature sizes, which complicates the processing and manufacturing of image sensor devices.
Innovation Solution
A method involving the formation of isolation structures and light-blocking structures in a semiconductor substrate to separate and electrically isolate light-sensing regions, using etch stop layers, insulating layers, and light-blocking materials to reduce optical and electrical crosstalk, and incorporating reflective grids and anti-reflection coatings to enhance light sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes are reduced to increase functional density, then the number of interconnected devices per chip area increases, but fabrication processes become more difficult and manufacturing reliability decreases
Solution Approach 1:
The patent divides the semiconductor substrate into multiple isolated regions using isolation structures (trenches filled with dielectric material) and light-blocking structures. This segmentation allows each pixel region to be independently formed and processed, enabling higher functional density while maintaining fabrication reliability through modular processing approaches.
Solution Approach 2:
The patent implements different structural characteristics in different regions of the substrate. Etch stop layers are selectively positioned at specific depths in certain regions, and isolation structures are tailored to local requirements. This local customization allows optimization for high-density integration while maintaining manufacturability in each specific area.
2Reliability
If isolation structures are formed to separate light-sensing regions, then optical and electrical crosstalk is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent combines multiple functions into integrated structures. The etch stop layers serve both as process control elements during fabrication and as part of the final isolation architecture. Light-blocking structures are integrated with the isolation trenches, eliminating the need for separate processing steps and reducing overall device complexity while maintaining effective signal isolation.
Solution Approach 2:
The isolation structures perform multiple functions simultaneously: they provide electrical isolation between adjacent pixels, optical isolation through light-blocking materials, mechanical support, and process alignment references. This multi-functionality reduces the need for additional dedicated structures, thereby reducing overall device complexity while achieving reliable signal isolation.
3Manufacturing precision
If multiple processing steps are used to form isolation and light-blocking structures, then manufacturing precision is improved, but productivity and manufacturing efficiency decrease
Solution Approach 1:
The patent performs preliminary formation of etch stop layers at specific depths before subsequent processing steps. These pre-formed layers serve as templates and alignment references for later isolation structure formation, ensuring high manufacturing precision while reducing the number of iterative adjustment steps needed, thereby improving overall manufacturing efficiency.
Solution Approach 2:
The etch stop layers act as intermediary structures that facilitate the transition between different processing stages. They provide a stable reference framework that enables precise formation of isolation structures without requiring complex real-time control, thus maintaining manufacturing precision while simplifying the overall process flow and improving productivity.
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 proposed method improves the reliability and efficiency of image sensor devices by reducing optical and electrical crosstalk, enhancing light sensing capabilities, and improving manufacturing yield.
Implementation Method 1
The light-blocking structure is between each two adjacent light-sensing regions. The light-blocking structure blocks light to prevent the light from traveling between the adjacent light-sensing regions.
Implementation Method 2
incorporating reflective grids and anti-reflection coatings to enhance light sensing
Data Source
AI summary
An image sensor device is provided. The image sensor device includes a substrate having a front surface, a back surface, and a light-sensing region. The image sensor device includes a first isolation structure extending from the front surface into the substrate. The first isolation structure surrounds a first portion of the light-sensing region, the first isolation structure has an etch stop layer, the etch stop layer has an end portion, and the end portion has an H-like shape. The image sensor device includes a second isolation structure extending into the substrate from the back surface to the end portion. The second isolation structure surrounds a second portion of the light-sensing region.