Image Sensor Layer Stack for Compact Contamination Protection
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Solution Overview
Problem
Conventional image sensors face challenges in reducing size while maintaining performance and reliability, particularly due to inadequate protection of color filters and microlenses, which leads to contamination and increased size of semiconductor packages.
Innovation Solution
The implementation of a color filter cover layer and two capping layers in the image sensor design, where the color filter cover layer is conformally coated on the color filters and the second capping layer is conformally coated on the microlens, providing protection and reducing the overall size of the semiconductor package.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional image sensor design is used without additional protective layers, then manufacturing is simpler, but the color filters and microlenses are exposed to contamination leading to reduced reliability
Solution Approach 1:
The patent introduces a color filter cover layer as an intermediary protective element between the color filters and the external environment. This cover layer acts as a mediator that prevents contamination from reaching the color filters and microlenses, thereby improving reliability without requiring complex redesign of the entire sensor structure
Solution Approach 2:
The patent employs sacrificial spacer layers that are intentionally designed to be removed after serving their temporary purpose of defining gaps between protective layers and color filters. These disposable spacer layers enable precise positioning during manufacturing and are subsequently eliminated, simplifying the final structure while maintaining protection during critical phases
2Reliability
If the image sensor includes multiple protective layers, then reliability is improved, but the package size increases
Solution Approach 1:
The patent utilizes thin film structures for the color filter cover layer and sacrificial spacer layers. These thin protective films provide adequate contamination protection while occupying minimal vertical space, thus improving reliability without significantly increasing the overall package volume of the image sensor
Solution Approach 2:
The patent implements a nested structure where the color filter cover layer is positioned within the existing sensor architecture, and sacrificial spacer layers are embedded within the gaps between the cover layer and color filters. This nested arrangement allows multiple protective elements to coexist in a compact configuration, minimizing package size expansion while enhancing protection
3Stability of the object's composition
If conformal coating is applied to the color filter cover layer, then protection uniformity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies conformal coating to the color filter cover layer as a preliminary protective measure before final assembly and operation. This preliminary coating ensures uniform protection across the entire surface of the cover layer and surrounding structures, establishing a consistent protective barrier that maintains stability throughout the sensor's lifecycle
Solution Approach 2:
The patent employs conformal coating technology that automatically adjusts coating parameters to achieve uniform thickness across complex three-dimensional structures. This parameter control ensures that the protective layer maintains consistent properties throughout, improving reliability without requiring excessively tight manufacturing tolerances
Data Source
AI summary
An image sensor includes a pixel, a rear side anti-reflective layer on the pixel, a color filter on the rear side anti-reflective layer, a color filter cover layer on the color filter, a passivation layer on the color filter cover layer, a microlens on the passivation layer, a first capping layer on the microlens, and a second capping layer on the first capping layer.