CMOS Image Sensor Opaque Layer Prevents Metal Line Reflection
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Solution Overview
Problem
CMOS image sensors face image quality degradation due to diffused reflection caused by metal lines obstructing the light path through transparent device isolation layers between microlenses.
Innovation Solution
An opaque layer is introduced on the device protecting layer adjacent to the microlenses to prevent light interference from metal lines, ensuring that the metal lines do not overlap with the photodiodes and thus do not affect incident light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transparent device isolation layer is used between microlenses, then light transmission is improved, but diffused reflection from metal lines degrades image quality
Solution Approach 1:
An opaque layer is introduced as an intermediary element between the metal lines and the light path. This layer blocks light from reaching the metal lines, preventing diffused reflection while maintaining the transparency of the device isolation layer for necessary light transmission to photodiodes.
Solution Approach 2:
The opaque layer is selectively positioned only in regions where metal lines are present and would interfere with light paths to photodiodes. This localized application maintains light transmission in areas where metal lines are absent, preserving overall light transmission efficiency while eliminating harmful reflection only where needed.
2Object-affected harmful factors
If an opaque layer is added to prevent diffused reflection, then image quality is improved, but device complexity increases
Solution Approach 1:
The opaque layer is integrated into the existing device structure by combining it with the device isolation layer or positioning it within the interlayer dielectric structure. This merging approach adds the anti-reflection function without creating a completely separate structural system, thereby limiting the increase in device complexity.
Solution Approach 2:
The opaque layer serves multiple functions: it prevents diffused reflection from metal lines, can act as an additional isolation layer, and provides a planar surface for subsequent processing steps. This multi-functionality reduces the need for separate dedicated components, thereby limiting complexity increase.
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 opaque layer effectively eliminates diffused reflection, enhancing the image quality by preventing light interference from metal lines, thereby improving the overall performance of the CMOS image sensor.
Implementation Method 1
A microlens 22 is then formed on the device protecting layer 20... A method of fabricating a CMOS image sensor according to the related art is explained with reference to the attached drawing as follows
Implementation Method 2
An opaque layer is introduced on the device protecting layer adjacent to the microlenses to prevent light interference from metal lines... The opaque layer effectively eliminates diffused reflection
Data Source
AI summary
A CMOS image sensor and fabricating method thereof can enhance the quality of the image sensor by preventing unnecessary diffused reflection of light by providing an opaque filter layer next to a microlens. The CMOS image sensor includes a photodiode, an insulating interlayer, a metal line, a device protecting layer, a microlens on the device protecting layer and overlapped with the photodiode, and an opaque layer pattern on the device protecting layer next to the microlens.