Image Sensor Pillar Array Structure for Flare and Reflection Reduction
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Solution Overview
Problem
Image sensors experience reduced light absorption and generate petal flares due to reflection and diffraction at the interface between microlens and semiconductor substrates with different refractive indexes.
Innovation Solution
Incorporating a pillar array layer with varying pillar heights, pitches, and shapes between photodiodes to minimize reflection and diffraction, using tapered structures with gradually changing refractive indexes to extend light paths and enhance absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a microlens layer and semiconductor substrate with different refractive indexes are used, then light focusing capability is improved, but reflection and petal flares occur reducing light absorption
Solution Approach 1:
A pillar array layer is introduced as an intermediary structure between the microlens layer and semiconductor substrate. This pillar array layer has a refractive index that gradually transitions from the microlens layer to the semiconductor substrate, reducing the abrupt refractive index difference and thereby minimizing reflection and diffraction effects while maintaining light focusing capability
Solution Approach 2:
The refractive index parameter is gradually changed through the pillar array layer structure. By varying the pillar height, pitch, and shape, the effective refractive index transitions smoothly from the microlens layer to the semiconductor substrate, reducing reflection and improving light absorption
2Loss of energy
If light passes through microlens layer and semiconductor substrate, then light absorption by photodiodes occurs, but reflection reduces absorbed light
Solution Approach 1:
The pillar array layer serves as an intermediary that reduces reflection losses by providing a gradual refractive index transition, thereby increasing the amount of light that reaches and is absorbed by the photodiodes
3Reliability
If light passes through microlens layer and semiconductor substrate, then image sensing occurs, but diffraction generates petal flares reducing performance
Solution Approach 1:
The pillar array layer acts as an intermediary that reduces diffraction effects by providing a gradual refractive index transition, thereby minimizing petal flare generation and improving image sensor performance
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 solution reduces petal flares by up to 32% and maintains quantum efficiency at 20%, thereby improving image sensor performance.
Implementation Method 1
The light may generate reflection when the light passes through the microlens layer and the semiconductor substrate
Implementation Method 2
due to the diffraction of the light, the image sensor may generate petal flares
Implementation Method 3
The microlens layer and the semiconductor substrate have different refractive indexes
Data Source
AI summary
The image sensor includes a semiconductor substrate, a pillar array layer, a planar layer, and a microlens layer. The semiconductor substrate includes a first photodiode and a second photodiode. The pillar array layer is disposed on the semiconductor substrate, the pillar array layer includes a first pillar array disposed above the first photodiode and a second pillar array disposed above the second photodiode. The first pillar array includes a plurality of first pillar structures, the second pillar array includes a plurality of second pillar structures, all the first pillar structures have a first height, and all the second pillar structures have a second height. The planar layer is disposed on the pillar array layer. The microlens layer is disposed on the planar layer.