ISFET Microwell Formation Using Composite Insulating Layers
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Solution Overview
Problem
Ion-sensitive field effect transistors (ISFETs) used in detecting analytes in fluids face accuracy and sensitivity issues due to pH changes influenced by adjacent environments and buffering interactions, leading to lower sensitivity and higher noise in nucleotide sequencing applications.
Innovation Solution
A method involving the formation of sensor arrays with a first inorganic material layer, a polymeric material layer, and a second inorganic material layer, where the polymeric layer is etched to define microwells over sensor pads, reducing buffering effects and enhancing signal-to-noise ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional sensor array structure is used, then the device complexity is low, but the measurement precision deteriorates due to pH crosstalk and buffering effects from adjacent environments
Solution Approach 1:
The sensor array is segmented into isolated microwell structures, where each well physically separates the detection environment from adjacent regions. This segmentation prevents pH crosstalk between neighboring sensors and eliminates buffering effects from surrounding materials, thereby improving measurement precision without significantly increasing overall device complexity
Solution Approach 2:
The microwell structure provides a localized controlled environment with specific surface properties (low buffering material coating) only at the sensor active area. This local quality modification ensures that pH changes are confined to the immediate detection zone without being influenced by adjacent environments, enhancing detection accuracy while maintaining simple overall device architecture
2Reliability
If micrawells are formed with multiple layers, then the buffering effects are reduced and sensitivity is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The micrawell structure employs a composite multi-layer design consisting of a first inorganic material layer, a polymeric material layer, and a second inorganic material layer. Each layer serves a specific function: the inorganic layers provide structural integrity and etch selectivity, while the polymeric layer provides a low buffering surface. This composite structure reduces buffering effects and improves signal-to-noise ratio while using standard semiconductor manufacturing techniques
Solution Approach 2:
The polymeric material layer acts as an intermediary between the inorganic layers and the sensor pad, providing a low buffering surface that mediates the interaction between the aqueous environment and the sensor. This intermediary layer prevents direct contact between the sensor and high-buffering surfaces, thereby improving reliability and signal quality while maintaining manufacturability through conventional deposition and etching processes
Data Source
AI summary
A method of forming a sensor component includes forming a first layer over a sensor pad of a sensor of a sensor array. The first layer includes a first inorganic material. The method further includes forming a second layer over the first layer. The second layer includes a polymeric material. The method also includes forming a third layer over the second layer, the third layer comprising a second inorganic material; patterning the third layer; and etching the second layer to define a well over the sensor pad of the sensor array.