CMOS ChemFET Array Layout for Dense pH Sensing Pixels
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Solution Overview
Problem
Conventional ISFET arrays face limitations in achieving high pixel density and accurate analyte measurements due to large pixel size and sensitivity issues, particularly in pH range measurements and DNA sequencing applications, where cost and throughput are significant challenges.
Innovation Solution
The development of large-scale chemically-sensitive FET arrays with reduced pixel size and increased pixel density, utilizing CMOS processing technologies to enhance signal-to-noise ratio and data acquisition speed, and incorporating microfluidics for efficient analyte delivery and measurement in nucleic acid sequencing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ISFET array designs are used, then device complexity is reduced and ease of manufacture is improved, but pixel density is limited and measurement precision deteriorates
Solution Approach 1:
The patent divides the sensor array into modular pixel units, each containing an ISFET sensor element with associated readout circuitry. This segmentation allows independent optimization of each pixel while maintaining overall array functionality, enabling higher pixel density without proportionally increasing total device complexity
Solution Approach 2:
The patent combines the ISFET sensor element, gate structure, and readout circuitry into integrated pixel units. This merging reduces the number of discrete components and interconnections required, allowing higher pixel density while controlling overall device complexity through functional integration
2Productivity
If pixel size is reduced to increase pixel density, then productivity is improved, but signal-to-noise ratio deteriorates and measurement precision is affected
Solution Approach 1:
The patent combines multiple functional elements (sensor, gate, readout circuitry) into integrated pixel units, which improves packing density and data acquisition speed while maintaining adequate signal quality through optimized internal connections
Solution Approach 2:
The patent replaces conventional readout methods with field-effect transistor-based electronic readout circuitry integrated at each pixel. This substitution enables parallel readout of multiple pixels, significantly increasing productivity while the electronic design maintains signal-to-noise ratio through low-impedance connections and buffered amplification
3Area of stationary object
If pixel size is reduced to increase pixel density, then area utilization is improved, but sensitivity deteriorates
Solution Approach 1:
The patent applies different design optimizations to different regions within each pixel: the ISFET sensor region is optimized for sensitivity with adequate active area, while the readout circuitry region is optimized for compactness. This local quality differentiation maintains sensitivity despite reduced overall pixel size
Solution Approach 2:
The patent merges the sensor element and readout circuitry into a single integrated pixel unit with optimized spatial arrangement. This merging allows efficient use of pixel area while maintaining sensor sensitivity through proper positioning and connection of the sensing 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
This approach enables high-density, high-speed analyte measurement and DNA sequencing by reducing pixel size, increasing pixel density, and improving measurement accuracy and throughput, addressing the limitations of conventional ISFET arrays in cost and efficiency.
Implementation Method 1
chemically-sensitive field effect transistor (chemFET) configured to detect changes in concentration of an analyte in a chemical or biological process
Implementation Method 2
chemically-sensitive FET arrays with reduced pixel size and increased pixel density, utilizing CMOS processing technologies to enhance signal-to-noise ratio
Data Source
AI summary
Methods and apparatus relating to very large scale FET arrays for analyte measurements. ChemFET (e.g., ISFET) arrays may be fabricated using conventional CMOS processing techniques based on improved FET pixel and array designs that increase measurement sensitivity and accuracy, and at the same time facilitate significantly small pixel sizes and dense arrays. Improved array control techniques provide for rapid data acquisition from large and dense arrays. Such arrays may be employed to detect a presence and/or concentration changes of various analyte types in a wide variety of chemical and/or biological processes. In one example, chemFET arrays facilitate DNA sequencing techniques based on monitoring changes in hydrogen ion concentration (pH), changes in other analyte concentration, and/or binding events associated with chemical processes relating to DNA synthesis.