Pixel Isolation Structure for Image Sensor Warpage Control
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Solution Overview
Problem
Current image sensors face challenges in effectively isolating unit pixels and managing stress during manufacturing, leading to issues like warpage and inefficient pixel isolation.
Innovation Solution
The image sensor incorporates a pixel isolation structure with a buried conductive pattern and insulating structure, where the buried conductive pattern extends into the substrate, and the insulating structure covers the lower surface, with varying widths and levels to optimize pixel separation and reduce stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel isolation structure is used, then manufacturing is simpler, but pixel isolation effectiveness is insufficient and warpage control is poor
Solution Approach 1:
The pixel isolation structure is divided into multiple functional segments: a first isolation layer for basic pixel separation, a second isolation layer for enhanced isolation, and a buried conductive pattern for stress management. Each segment performs a specific function, collectively achieving superior pixel isolation and warpage control while maintaining manageable complexity through modular design.
Solution Approach 2:
The isolation structure employs composite material layers including insulating materials for electrical isolation and conductive materials for stress compensation. This combination of different material properties enables simultaneous achievement of effective pixel isolation and warpage control, resolving the contradiction between isolation effectiveness and structural complexity.
2Reliability
If the insulating structure width is uniform, then manufacturing is easier, but stress management is insufficient leading to warpage
Solution Approach 1:
The insulating structure implements local quality variation where the width differs at different vertical levels. The first level has a narrower width while the second level has a wider width, creating specific stress distribution patterns that effectively control warpage. This localized dimensional variation optimizes stress management while remaining compatible with standard manufacturing processes.
Solution Approach 2:
The patent changes the geometric parameter (width) of the insulating structure at different levels to achieve stress management. By varying the width parameter from the first level to the second level, the structure creates controlled stress fields that prevent warpage, demonstrating parameter change as a solution to the warpage control challenge.
3Reliability
If the buried conductive pattern extends deeper into the substrate, then stress management improves, but manufacturing complexity increases
Solution Approach 1:
The buried conductive pattern is formed in advance during the manufacturing process, extending into the substrate before subsequent isolation layers are deposited. This preliminary formation of the conductive pattern establishes the stress management foundation early, simplifying subsequent manufacturing steps while achieving effective stress control.
Solution Approach 2:
The buried conductive pattern acts as an intermediary element between the substrate and the overlying isolation structures. It mediates stress distribution by providing a conductive path that compensates for stress, enabling effective stress management without requiring complex manufacturing interventions at later stages.
Data Source
AI summary
An image sensor comprising a substrate including a plurality of unit pixels and including a first surface facing a first direction and a second surface facing a second direction opposite to the first direction, and a pixel isolation structure passing through the substrate in the second direction between the unit pixels, wherein the pixel isolation structure includes a buried conductive pattern extending from the second surface of the substrate into an inside of the substrate, and an insulating structure covering a lower surface of the buried conductive pattern and extending between the substrate and the buried conductive pattern, a first level and a second level that is under the first level being defined, the lower surface of the buried conductive pattern being positioned at the second level.