Curved Mirror BSI CMOS Image Sensor Quantum Efficiency
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Solution Overview
Problem
Conventional backside illumination (BSI) CMOS image sensors have limitations in quantum efficiency due to the inability to effectively reflect incident light back to the light sensing area, which restricts their sensitivity and performance.
Innovation Solution
A BSI CMOS image sensing process that forms curved mirrors on the active side of a substrate, allowing incident light to be reflected back to the light sensing area by curving the substrate and forming a reflective layer, thereby enhancing quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional BSI image sensor structure is used, then the sensor can be integrated into conventional semiconductor processes with low cost and high integration, but the quantum efficiency is limited due to inability to effectively reflect incident light back to the light sensing area
Solution Approach 1:
The patent applies curvature to the active side of the substrate to form a curved reflective surface. This curved mirror structure reflects incident light that penetrates the light sensing area back onto the photodiodes, increasing the probability of photon absorption and thereby improving quantum efficiency without adding complex external optical components
Solution Approach 2:
The patent introduces a reflective layer as an intermediary element on the active side of the substrate. This reflective layer acts as a mediator to redirect light that would otherwise be lost, bouncing it back through the light sensing area to enhance the interaction between light and photodiodes, thus improving quantum efficiency
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 process significantly increases the quantum efficiency of the light sensing area by reflecting incident light back onto the photodiodes, improving the sensor's sensitivity and performance.
Implementation Method 1
forms at least a curved mirror on an active side of a substrate, so that incident light penetrating a light sensing area in the substrate can be reflected back to the light sensing area
Data Source
AI summary
A backside illumination (BSI) CMOS image sensing process includes the following steps. A substrate having an active side is provided. A curving process is performed to curve the active side. A reflective layer is formed on the active side, so that at least a curved mirror is formed on the active side.