Backside-Illuminated CMOS Biosensor for Wavelength-Specific Fluorescence
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Solution Overview
Problem
Existing CMOS image sensors face challenges in efficiently analyzing fluorescence or chemiluminescence for biological or chemical analysis, particularly in DNA sequencing, due to limitations in light detection and separation of wavelengths.
Innovation Solution
A biosensor utilizing a backside illumination (BSI) CMOS image sensor with integrated color filters, microlenses, and optimized photodiodes to enhance light detection and wavelength specificity, enabling efficient measurement of fluorescence or chemiluminescence from biological or chemical samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional CMOS image sensors are used for biological or chemical analysis, then the device structure is simple and manufacturing is easier, but the light detection efficiency and wavelength separation capability are insufficient
Solution Approach 1:
The sensor is divided into distinct functional regions: light sensing area with photodiodes for detecting fluorescence/chemiluminescence signals, and electronic circuit area with MOS transistors and wiring for signal processing. This segmentation allows each region to be optimized for its specific function, improving overall measurement precision while managing device complexity through functional specialization.
Solution Approach 2:
The patent employs backside illumination architecture where light enters the sensor from the opposite side of where electrical connections are made. This dimensional reversal allows photodiodes to be positioned closer to the light source without interference from metal wiring and circuitry, significantly improving light detection efficiency and reducing destructive interference while maintaining manageable device complexity.
2Measurement precision
If backside illumination CMOS sensors are used, then light detection efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The sensor structure is designed and fabricated with backside illumination architecture from the outset, with photodiodes, color filters, and microlenses positioned and optimized for light reception before final assembly. This preliminary configuration ensures that alignment precision requirements are met during manufacturing, allowing the backside illumination design to achieve improved light detection efficiency without compromising manufacturability.
3Measurement precision
If color filters are added to separate wavelengths, then wavelength specificity is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
Color filters are integrated directly into the sensor structure, merging the wavelength separation function with the light detection architecture. This integration allows multiple wavelength channels to be processed simultaneously by different photodiode regions, improving wavelength specificity while reducing manufacturing complexity compared to external filter systems. The filters are fabricated as part of the standard CMOS sensor manufacturing process.
Solution Approach 2:
The sensor design incorporates multiple color filters (e.g., red, green, blue) that can simultaneously detect different wavelength ranges of fluorescence or chemiluminescence signals. This multi-functional approach allows a single sensor device to perform wavelength-specific detection across multiple channels, improving measurement precision while maintaining ease of manufacture through a unified sensor platform.
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 biosensor effectively separates and measures light emissions by wavelength, allowing for accurate identification of biological or chemical samples, particularly in DNA sequencing processes like sequencing-by-synthesis, sequencing-by-ligation, and pyrosequencing.
Implementation Method 1
The light is received by the photodiodes on a substrate and transformed into electrical signals of different intensity
Implementation Method 2
a BSI CMOS image sensor with integrated color filters, microlenses, and optimized photodiodes to enhance light detection and wavelength specificity
Implementation Method 3
microlenses may be placed in front of the photodiodes to direct light into the photodiodes
Data Source
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AI summary
A biosensor comprising a backside illumination CMOS image sensor including an electronic circuit layer and a photo-sensing layer over the electronic circuit layer is disclosed. The photo-sensing layer comprises a substrate layer (115) and a plurality of photodiodes (117), wherein a light receiving surface is defined by a surface of the photodiodes opposite to the electronic circuit layer. According to some embodiments, the biosensor further comprises a plurality of spots sized and functionalized to contain a nucleic acid macromolecule above the light receiving surface, a color filter material (127B) between each photodiode and each spot, a first metal layer (123B) over the substrate layer, wherein the first metal layer has a plurality of first openings over the plurality of photodiodes and the color filter materials are positioned in the plurality of first openings, a passivation layer (130) over the first metal layer and the plurality of color filter materials, a second metal layer (133B) over the passivation layer, wherein the second metal layer has a plurality of second openings over the plurality of color filter materials, and a plurality of micro-lenses (140A) over the second metal layer. Furthermore, a method of manufacturing the biosensor is described.