MEMS Pressure Sensor Using FET Gate Electrode Contact
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Solution Overview
Problem
Existing micro electro mechanical system (MEMS) sensors face challenges in sensitivity due to parasitic capacitance and complex manufacturing processes, particularly in pressure and acceleration sensing applications.
Innovation Solution
A micro electro mechanical device with a semiconductor layer, source/drain regions, a gate insulating film, and a movable gate electrode that contacts the insulating film to detect pressure, utilizing a temporary FET structure and comb-teeth shaped source-drain regions for improved accuracy and simplified manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the electrode area is increased to enhance sensitivity, then the sensitivity is improved, but the parasitic capacitance increases and the device area increases
Solution Approach 1:
The patent replaces the conventional electrostatic capacitance-based pressure detection mechanism with a FET-based detection mechanism. Instead of measuring changes in capacitance between electrodes, the invention uses a FET where pressure applied to the gate electrode modulates the channel current. This substitution eliminates the parasitic capacitance issues inherent in electrostatic sensors while maintaining high sensitivity through the FET's signal amplification capability.
Solution Approach 2:
The patent changes the detection parameter from electrostatic capacitance to FET channel current. By applying pressure to the gate electrode, the channel current is modulated according to the contact area between the gate electrode and gate insulating film. This parameter change enables high sensitivity detection without the parasitic capacitance problems that limit electrostatic sensor performance.
2Measurement precision
If a FET structure is used to achieve downsizing and sensitivity enhancement, then sensitivity and miniaturization are improved, but the steric structure becomes complicated and the manufacturing process becomes long and complicated
Solution Approach 1:
The patent merges the pressure sensor structure with a FET structure into a single integrated device. The gate electrode of the FET serves dual purposes: as the control electrode for the FET operation and as the pressure-sensitive element. This merging eliminates the need for separate sensor and FET structures, thereby simplifying the overall device structure and reducing manufacturing complexity while maintaining high sensitivity and miniaturization benefits.
Solution Approach 2:
The gate electrode is designed to serve multiple functions: it acts as the control electrode for FET operation, the pressure-sensitive element for detection, and the movable element that contacts the gate insulating film. This multi-functionality reduces the number of separate components needed, simplifying both the device structure and the manufacturing process while achieving high sensitivity and miniaturization.
3Measurement precision
If the electrode area is increased to enhance sensitivity, then the sensitivity is improved, but the device area increases
Solution Approach 1:
The patent replaces the electrostatic capacitance-based detection mechanism with a FET-based mechanism, eliminating the need for large electrode areas. The FET's current amplification capability provides high sensitivity even with minimal gate electrode area, as the channel current is strongly modulated by the gate voltage. This substitution allows high sensitivity detection in a compact area, resolving the contradiction between sensitivity and device area.
Solution Approach 2:
The patent changes the detection mechanism from electrostatic capacitance measurement to FET channel current measurement. This parameter change enables high sensitivity with small gate electrode areas because the FET provides signal amplification through its transconductance characteristic. The channel current changes significantly in response to small gate voltage changes, achieving high sensitivity without requiring large electrode areas.
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
Enhances sensitivity and miniaturization while simplifying the manufacturing process, allowing for accurate pressure detection and integration with semiconductor elements on a single chip, reducing complexity and increasing performance.
Implementation Method 1
a technique detecting pressure or the like by the change of the electrostatic capacitance between two electrodes
Data Source
AI summary
A micro electro mechanical device includes: a semiconductor layer; a source/drain region formed on both sides of a channel region within the semiconductor layer; a gate insulating film formed on the semiconductor layer; a cavity formed on the gate insulating film; and a gate electrode formed on the cavity, the gate electrode being movable so as to contact with the gate insulating film. In the device, a pressure applied on the gate electrode is detected by a contact area of the gate electrode and the gate insulating film.