Gas-Sensitive FET Floating Gate CMOS Integration
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Solution Overview
Problem
Current FET gas sensors face challenges with high manufacturing costs, difficulty in miniaturization and batch processing, high power consumption, and low sensitivity at room temperature, due to the use of special gate materials and structures.
Innovation Solution
The development of gas-sensitive FET structures using a CMOS process with a floating gate, lateral control gate, and reset switch, integrated with a sensing material layer such as zinc oxide nanorods, and optional heaters and temperature sensors, to enhance sensitivity and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If special gate materials such as porous Palladium or special structures such as suspended control gates are used, then gas sensing capability is improved, but manufacturing cost increases and miniaturization becomes more difficult
Solution Approach 1:
The patent changes the material parameter of the gate from special materials like porous Palladium to standard CMOS-compatible materials such as polysilicon or metal gates. This parameter change maintains gas sensing capability through the floating gate structure while enabling compatibility with standard manufacturing processes, thereby reducing production costs and facilitating miniaturization
Solution Approach 2:
The patent uses a floating gate structure that copies the essential function of special gate materials by trapping charges to modulate the channel conductivity. This floating gate can be charged through tunneling or direct contact with sensing materials, replicating the gas sensing effect without requiring expensive special materials, thus resolving the contradiction between sensing capability and manufacturing cost
2Measurement precision
If special gate materials such as porous Palladium or suspended control gates are used, then gas sensing capability is improved, but miniaturization and batch processing become more difficult
Solution Approach 1:
The floating gate structure serves multiple functions: it acts as the control gate for the FET, stores charge from gas sensing events, and modulates the channel conductivity. This multi-functional design eliminates the need for separate sensing structures and control gates, enabling miniaturization and compatibility with standard CMOS batch processing while maintaining gas sensing capability
Solution Approach 2:
The patent merges the gate control function with the charge storage function into a single floating gate structure. By combining these functions and integrating them with standard CMOS transistor fabrication, the device complexity is reduced, enabling easier miniaturization and batch processing compared to structures with separate sensing elements and control gates
3Measurement precision
If conventional FET gas sensors operate at elevated temperatures, then sensitivity is improved, but power consumption increases
Solution Approach 1:
The floating gate structure enables the sensor to operate at room temperature by utilizing charge trapping and release mechanisms that occur naturally at lower temperatures. The floating gate automatically modulates the channel conductivity in response to gas molecules, eliminating the need for external heating to enhance sensitivity, thus reducing power consumption while maintaining sensing capability
Solution Approach 2:
The patent changes the operating temperature parameter from elevated temperatures to room temperature by modifying the gate structure to a floating gate. This parameter change allows the sensor to achieve adequate sensitivity without thermal activation, thereby significantly reducing power consumption while maintaining functional performance
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 results in a more cost-effective, miniaturized, and sensitive gas sensor array with reduced power consumption, capable of detecting hazardous gases at room temperature, such as acetone in human breath for diabetes diagnosis.
Implementation Method 1
A sensing material layer can be positioned over the floating gate
Implementation Method 2
A floating gate disposed within the body can comprise metal at a top surface of the intermediate layer
Implementation Method 3
The passivation layer can be etched over the control gate, and the control gate can be electrically coupled to a predetermined voltage
Data Source
AI summary
Aspects describe gas sensitive field effect transistor (FET) structures, a gas sensitive FET array including the disclosed gas sensitive FET structures, and methods of manufacturing and using the same. In one example, a gas sensitive FET structure can include a body comprising a substrate layer, an intermediate layer over the substrate layer, and a passivation layer over the intermediate layer. Primary terminals disposed within the body can include at least one source terminal, at least one drain terminal and at least one gate terminal. A floating gate disposed within the body can comprise metal at a top surface of the intermediate layer. The passivation layer can be etched over the floating gate, and the floating gate can be electrically coupled to the gate terminal of the primary terminals. A sensing material layer can be positioned over the floating gate. A reset element can be included for resetting the floating gate.