Curved Micro-Mirrors for CMOS Image Sensor Light Capture
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Solution Overview
Problem
As image sensors and their pixels become smaller, existing technologies struggle to capture incident light efficiently, leading to reduced light conversion into electrical signals, particularly in backside illuminated devices where flat mirrors can cause light loss or crosstalk.
Innovation Solution
Integration of curved micro-mirrors over the photodiode active area in CMOS image sensors to reflect passthrough light back onto the photodiode, enhancing light capture and signal generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the size of image sensors and pixels is reduced to achieve further integration, then device complexity and integration density are improved, but light capture efficiency deteriorates
Solution Approach 1:
The patent applies curvature to the mirror surface, transitioning from a flat mirror to a curved mirror structure. This curvature enables the mirror to reflect light that passes through the photodiode back onto the photodiode surface, thereby improving light capture efficiency in smaller pixels while maintaining high integration density.
2Loss of energy
If a flat mirror is used in backside illuminated devices to reflect light back through the photodiode, then light reflection is achieved, but light loss and crosstalk increase
Solution Approach 1:
The curved mirror surface is designed to reflect light back onto the photodiode surface more effectively than a flat mirror. The curvature allows for better control of light paths, reducing light loss and minimizing crosstalk between adjacent pixels by directing reflected light precisely onto the intended photodiode region.
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 curved micro-mirrors effectively redirect and capture more incident light, increasing the electrical signal generated by the photodiode, thereby improving the efficiency of light utilization in image sensors.
Implementation Method 1
The curved micro-mirrors reflect light that has passed through the collection area back into the photodiode
Data Source
AI summary
The invention involves the integration of curved micro-mirrors over a photodiode active area (collection area) in a CMOS image sensor (CIS) process. The curved micro-mirrors reflect light that has passed through the collection area back into the photo diode. The curved micro-mirrors are best implemented in a backside illuminated device (BSI).