Image Sensor Light-Absorbing Layer for Parasitic Reflection Reduction
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Solution Overview
Problem
Current image sensors suffer from defects such as image deformation and ghost images, particularly when capturing scenes with very bright objects like the sun, due to parasitic light reflections from metallizations and metal elements, leading to halos and ghost images.
Innovation Solution
Incorporating a light-absorbing material with metal particles, typically 100-500 nm thick, to cover metal elements on the illumination-facing side of the image sensor, which absorbs parasitic light rays instead of reflecting them, thereby reducing image defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal elements (metallizations) are used for interconnection and control circuits in the image sensor, then electrical connectivity and device functionality are achieved, but parasitic light reflections occur causing image defects such as halos and ghost images
Solution Approach 1:
An absorbent material layer is introduced as an intermediary between the metal elements and the incident light. This layer absorbs parasitic light rays before they can reflect off the metal surfaces, thereby eliminating image defects while preserving the electrical functionality of the metal interconnection elements.
Solution Approach 2:
The metal elements inherently reflect light, which causes image defects. The invention converts this harmful reflection property into a beneficial configuration by strategically placing absorbent material to target only the parasitic reflections from specific metal elements, while allowing useful light to reach the photodiodes.
2Manufacturing precision
If absorbent material is added to cover metal elements to reduce parasitic reflections, then image quality improves, but device structure and manufacturing process become more complex
Solution Approach 1:
The absorbent material is not applied uniformly across the entire sensor surface but is selectively positioned to cover only specific metal elements that generate parasitic reflections. This localized application approach improves image quality where needed while minimizing additional structural complexity and manufacturing overhead.
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
Significantly reduces parasitic reflections and associated image defects like halos and ghost images by effectively managing light absorption over metal elements in both front- and back-illuminated image sensor structures.
Implementation Method 1
the metal element is at least partially covered, on the side of the face intended to receive illumination, with an absorbent material absorbing the light rays
Data Source
AI summary
The invention relates to an image sensor and method for reducing image defects. A photoconversion area is formed in a semiconductor layer. An insulating layer formed over the semiconductor layer contains a metal element. A lens over the insulting layer is positioned opposite the photoconversion area to focus light on it. A layer of light-absorbing material is deposited on the side of the metal element facing the lens to prevent reflection of parasitic light rays within the image device.