Capacitive Pressure Sensor with Cavity Structure
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Solution Overview
Problem
Existing silicon-based MEMS pressure sensors have limitations in sensitivity and cost due to the need for special materials like piezoresistive or piezoelectric materials, and they struggle with large-area applications.
Innovation Solution
A pressure sensor design featuring a substrate with a sensing transistor that includes a first active layer, a first sensing gate, and a cavity structure between the active layer and the sensing gate, which enhances sensitivity and reduces production costs by eliminating the need for complex special materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If silicon-based MEMS technology is used to achieve micrometer or nanometer scale internal structure, then manufacturing precision is improved, but sensitivity remains relatively low and material cost increases due to requiring special piezoresistive or piezoelectric materials
Solution Approach 1:
The patent replaces the mechanical piezoresistive or piezoelectric effect-based detection system with a capacitive detection system. The sensing transistor uses capacitance changes between the gate electrode and active layer to detect pressure, eliminating the need for special piezoresistive or piezoelectric materials while maintaining high sensitivity.
Solution Approach 2:
The patent changes the detection parameter from resistance or charge (in piezoresistive/piezoelectric materials) to capacitance. By forming a capacitor structure between the gate electrode and active layer, the system detects pressure through capacitance changes, which provides higher sensitivity without requiring special materials.
2Reliability
If special piezoresistive or piezoelectric materials are used to achieve pressure detection, then detection function is improved, but material cost increases
Solution Approach 1:
The patent replaces expensive special materials (piezoresistive or piezoelectric materials) with inexpensive common materials such as silicon oxide or silicon nitride for the insulating layer, and standard conductive materials for electrodes. This substitution dramatically reduces material cost while maintaining pressure detection functionality through capacitive sensing.
Solution Approach 2:
The patent substitutes the material-based detection mechanism (relying on special piezoresistive or piezoelectric materials) with a structural-based capacitive detection mechanism. The pressure detection function is achieved through physical capacitance changes in a standard transistor structure, eliminating dependence on expensive special materials.
3Manufacturing precision
If silicon-based MEMS technology is used, then manufacturing precision is improved, but device complexity increases due to requiring special materials and processes
Solution Approach 1:
The patent makes the sensing transistor serve multiple functions: it acts as both the pressure sensing element and the signal processing element. The same transistor structure that forms the capacitive sensor also provides the readout circuitry, eliminating the need for separate specialized components and simplifying the overall device architecture.
Solution Approach 2:
The patent replaces the complex material system (requiring piezoresistive or piezoelectric materials with specific properties) with a universal capacitive sensing approach that can be implemented using standard semiconductor materials and processes, thereby reducing device complexity.
4Ease of manufacture
If conventional pressure sensor designs are used, then manufacturing is simplified, but detection sensitivity remains low
Solution Approach 1:
The patent changes the detection parameter to capacitance and optimizes the capacitor structure (gate electrode and active layer separation) to maximize sensitivity. By controlling the distance and area between the gate and active layer, the system achieves high detection sensitivity using standard manufacturing processes.
Solution Approach 2:
The patent substitutes conventional low-sensitivity detection mechanisms with a capacitive detection mechanism that provides higher sensitivity. The capacitive coupling between the gate electrode and active layer creates a more sensitive response to pressure-induced displacement, achieving high sensitivity without complicating the manufacturing process.
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 proposed pressure sensor achieves high detection sensitivity and low production costs by utilizing a cavity structure that deforms under external pressure, changing capacitance and output current, thereby effectively detecting different pressing forces.
Implementation Method 1
a cavity structure, provided between the first active layer and the first sensing gate, and overlapping with the first sensing gate
Data Source
AI summary
A pressure sensor includes a substrate and a sensing transistor, and the sensing transistor includes: a first active layer, a first sensing gate and a cavity structure. The first active layer is provided on the substrate. The first sensing gate is provided on a side of the first active layer away from the substrate. The cavity structure is provided between the first active layer and the first sensing gate and overlaps with the first sensing gate.