Image Sensor Optical Black Barrier Against Adhesive Permeation
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Solution Overview
Problem
Current image sensors face challenges in enhancing sensitivity, particularly due to issues related to light blocking and adhesive material permeation, which can degrade image quality.
Innovation Solution
The integration of a blocking bar with a length greater than micro and dummy lenses over the optical black region, surrounded by a curved top surface, helps prevent adhesive material from reaching the pixel array region and reduces sensitivity deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive material is applied over the optical black region, then the structural integrity is improved, but the adhesive material permeates to the pixel array region causing sensitivity degradation
Solution Approach 1:
The optical black region is segmented into multiple zones: a first optical black region adjacent to the pixel array region, a second optical black region adjacent to the pad region, and a third optical black region between them. This segmentation allows selective placement of adhesive material in the second and third regions while protecting the first region from adhesive permeation, thus maintaining both structural integrity and sensitivity.
Solution Approach 2:
A reflective layer is introduced as an intermediary between the adhesive material and the pixel array region. This reflective layer serves dual functions: it reflects light to improve image quality and acts as a barrier to prevent adhesive material from permeating to the pixel array region, thereby resolving the contradiction between structural integrity and sensitivity.
2Object-affected harmful factors
If the optical black region is made larger to improve light blocking, then the light blocking performance is improved, but the area available for pixel array is reduced
Solution Approach 1:
Different regions of the optical black structure are assigned different functions and properties. The first optical black region provides light blocking adjacent to the pixel array, the second optical black region provides structural support for adhesive bonding, and the third optical black region provides additional light blocking. This local differentiation allows the optical black region to perform multiple functions without uniformly increasing its area, thus balancing light blocking performance with pixel array area.
3Reliability
If a blocking bar is added to prevent adhesive permeation, then sensitivity is improved, but the device complexity increases
Solution Approach 1:
The blocking bar is merged with the reflective layer to form an integrated structure. This combination achieves two functions simultaneously: the blocking bar prevents adhesive material from reaching the pixel array region, while the reflective layer reflects light to improve image quality. By merging these functions into a single integrated structure, the solution prevents sensitivity degradation without proportionally increasing device complexity.
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 configuration effectively prevents adhesive material from permeating to the pixel array region, reducing the risk of sensitivity degradation and maintaining image sensor performance.
Implementation Method 1
Each of the pixels may include a photodiode (PD). The photodiode may convert incident light into an electrical signal.
Data Source
AI summary
An image sensor includes a substrate including a pixel array region and an optical black region surrounding the pixel array region, a micro lens over the pixel array region, a dummy lens over the optical black region, and a blocking bar over the optical black region. A length of the blocking bar is greater than a length of the micro lens and a length of the dummy lens. A top surface of the blocking bar is curved.