Optical Shield Planarization Layer Black Level Correction
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Solution Overview
Problem
Conventional methods for fabricating black level correction (BLC) pixels and color filters in image sensors face challenges due to mechanical and electrical stresses, exacerbated by temperature, humidity, and voltage changes, leading to undesirable electrical signals and performance issues in next-generation optical devices.
Innovation Solution
An optical shield layer is deposited after the color filter layer in a backside illuminated imaging system, with the color filters not being fabricated on a prior patterned metal topography, allowing the BLC pixels to experience a similar mechanical and electrical environment as light-receiving pixels, and an additional planarization layer is used to encapsulate the optical shield layer, reducing stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional methods are used to fabricate BLC pixels and color filters, then manufacturing process is simplified, but mechanical and electrical stresses increase leading to undesirable electrical signals
Solution Approach 1:
The patent inverts the conventional fabrication sequence by depositing the optical shield layer AFTER the color filter layer rather than before. This reversal allows the color filters to be fabricated on a planarized surface without patterned metal topography, eliminating mechanical stresses and undesirable electrical signals while maintaining manufacturing feasibility
2Ease of manufacture
If color filters are fabricated on prior patterned metal topography, then manufacturing sequence is conventional, but mechanical stresses and electrical noise increase
Solution Approach 1:
The patent extracts the optical shield layer from its conventional position beneath the color filters and relocates it to a position above the planarization layer. This separation removes the source of mechanical stress and electrical noise from the color filter fabrication process, eliminating harmful effects while maintaining the protective function of the shield
Solution Approach 2:
The patent performs planarization before color filter deposition, creating a flat surface in advance. This preliminary action eliminates the need to fabricate color filters on patterned metal topography, preventing mechanical stresses and electrical noise from occurring in the first place
3Ease of manufacture
If optical shield layer is deposited before color filter layer, then fabrication follows conventional sequence, but BLC pixels experience different mechanical and electrical environment than light-receiving pixels
Solution Approach 1:
The patent structures the layers so that both BLC pixels and light-receiving pixels experience the same mechanical and electrical environment. By depositing the optical shield after the color filter and using planarization, all pixels undergo identical processing conditions, ensuring uniform performance characteristics across different pixel types
Data Source
AI summary
A pixel array includes a plurality of photodiodes disposed in a semiconductor layer and arranged in the pixel array. A color filter layer is disposed proximate to the semiconductor layer. Light is to be directed to at least a first one of the plurality of photodiodes through the color filter layer. An optical shield layer is disposed proximate to the color filter layer. The color filter layer is disposed between the optical shield layer and the semiconductor layer. The optical shield layer shields at least a second one of the plurality of photodiodes from the light.