Periodic Backside Image Sensor Structure for Infrared Absorption
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
CMOS image sensors have a low absorption coefficient for high wavelength radiation due to their large energy bandgap, leading to poor quantum efficiency, and increasing the depth of photodetectors in the semiconductor substrate is costly and increases die size and crosstalk.
Innovation Solution
A high absorption image sensor is developed with a non-porous semiconductor layer on the front side and a porous semiconductor layer with a periodic structure on the back side, incorporating a high absorption layer with a low energy bandgap, which enhances radiation absorption and quantum efficiency without increasing substrate thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the depth of photodetectors in the semiconductor substrate is increased to improve radiation absorption, then quantum efficiency is improved, but manufacturing cost increases and die size increases
Solution Approach 1:
The patent employs a porous semiconductor layer with controlled porosity (30-70%) to enhance radiation absorption. The porous structure increases the effective surface area and light-trapping capability, allowing photodetectors to achieve high quantum efficiency without increasing substrate depth, thereby avoiding increased manufacturing cost and die size
Solution Approach 2:
The patent creates a composite structure combining a non-porous semiconductor layer and a porous semiconductor layer. This composite architecture leverages the advantages of both structures: the non-porous layer provides mechanical strength and standard photodetector functionality, while the porous layer enhances radiation absorption, achieving high quantum efficiency without increasing substrate thickness or manufacturing complexity
2Reliability
If the depth of photodetectors in the semiconductor substrate is increased to improve radiation absorption, then quantum efficiency is improved, but die size increases
Solution Approach 1:
The porous semiconductor layer with 30-70% porosity creates a three-dimensional light-trapping structure that enhances absorption within a compact footprint. This allows the photodetectors to achieve high quantum efficiency for high wavelength radiation without increasing the lateral dimensions or die size of the sensor
3Reliability
If the depth of photodetectors in the semiconductor substrate is increased to improve radiation absorption, then quantum efficiency is improved, but crosstalk increases
Solution Approach 1:
The porous layer enhances absorption of high wavelength radiation at the surface level, reducing the need for deep photodetector structures. This surface-level enhancement minimizes the interaction between adjacent photodetectors, thereby reducing crosstalk while maintaining high 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 solution achieves high quantum efficiency for high wavelength radiation, such as infrared, while maintaining low cost, die size, and crosstalk, enabling effective sensing without the need for a thick semiconductor substrate.
Implementation Method 1
A high absorption layer is formed lining the periodic structure on the back side of the semiconductor substrate. The high absorption layer is a semiconductor material with an energy bandgap less than that of the non-porous semiconductor layer.
Data Source
AI summary
An image sensor with high quantum efficiency is provided. In some embodiments, a semiconductor substrate includes a non-porous semiconductor layer along a front side of the semiconductor substrate. A periodic structure is along a back side of the semiconductor substrate. A high absorption layer lines the periodic structure on the back side of the semiconductor substrate. The high absorption layer is a semiconductor material with an energy bandgap less than that of the non-porous semiconductor layer. A photodetector is in the semiconductor substrate and the high absorption layer. A method for manufacturing the image sensor is also provided.