Cavityless Chip-Scale Image Sensor Package
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Solution Overview
Problem
Existing image sensors face issues with layer delamination and image artifacts due to light reflection from protective layers, particularly in chip-scale packages, which affect the quality of captured images.
Innovation Solution
A cavityless chip-scale image-sensor package is developed, featuring a substrate with a pixel array, a microlens array, and a low-index layer with a refractive index less than the microlens refractive index, where the low-index layer is conformal to the non-planar microlens surfaces, eliminating the need for a spacer and reducing reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional protective layer is added above the pixel array, then the pixel array is protected, but light reflection occurs causing image artifacts
Solution Approach 1:
A low-index layer with refractive index lower than the microlens material is introduced as an intermediary between the microlens array and the external environment. This low-index layer acts as an optical mediator that reduces the refractive index mismatch at interfaces, thereby minimizing light reflection and eliminating image artifacts while maintaining protective coverage over the pixel array.
2Stability of the object's composition
If a spacer is used to maintain distance between protective layers, then structural stability is achieved, but device complexity increases
Solution Approach 1:
The low-index layer serves multiple functions simultaneously: it provides optical protection, eliminates reflection artifacts, and maintains the necessary structural spacing between the microlens array and external environment. By merging these functions into a single integrated layer, the design eliminates the need for separate spacers and reduces overall device complexity while maintaining structural stability.
3Reliability
If multiple layers are stacked to protect the image sensor, then protection is enhanced, but layer delamination occurs
Solution Approach 1:
The patent employs a composite structure where the low-index layer is integrated with the microlens array and substrate. This composite design ensures mechanical and optical compatibility between layers, preventing delamination while maintaining enhanced protection. The low-index layer's refractive index is specifically chosen to be lower than the microlens material, creating a graded index structure that prevents interface defects and delamination.
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 enhances image quality by minimizing reflections and delamination, resulting in improved light transmittance and image clarity without the artifacts caused by traditional protective layers.
Implementation Method 1
The low-index layer has a first refractive index less than the lens refractive index. The low-index layer also includes a bottom surface, at least part of which is conformal to each non-planar microlens surface.
Data Source
AI summary
A cavityless chip-scale image-sensor package includes a substrate, a microlens array, and a low-index layer. The substrate includes a plurality of pixels forming a pixel array. The microlens array includes a plurality of microlenses each (i) having a lens refractive index, (ii) being aligned to a respective one of the plurality of pixels and (iii) having a non-planar microlens surfaces facing away from the respective one of the plurality of pixels. The low-index layer has a first refractive index less than the lens refractive index. The low-index layer also includes a bottom surface, at least part of which is conformal to each non-planar microlens surface. The microlens array is between the pixel array and the low-index layer.