MEMS Humidity Sensor Parallel Plate Capacitance Polyimide Film
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Solution Overview
Problem
Humidity sensors face low test sensitivity due to the small fringing capacitance used for measuring humidity, which affects the accuracy of humidity readings.
Innovation Solution
A micro-electro mechanical system (MEMS) humidity sensor utilizing parallel plate capacitance and integrating a polyimide film to enhance sensitivity, along with on-chip pressure and temperature measurement for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fringing capacitance is used for humidity measurement, then the sensor structure is simple, but test sensitivity is too low
Solution Approach 1:
The patent changes the capacitance measurement parameter from fringing capacitance to parallel plate capacitance. This parameter change fundamentally increases the capacitance magnitude and test sensitivity while maintaining a relatively simple MEMS sensor structure, directly resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent integrates a polyimide film with the MEMS sensor structure to form a composite humidity sensing system. The polyimide film enhances the sensitivity of the parallel plate capacitance measurement by responding to humidity changes, thereby improving test sensitivity without significantly increasing structural complexity
2Measurement precision
If parallel plate capacitance is used instead of fringing capacitance, then test sensitivity increases, but device complexity increases
Solution Approach 1:
The patent transitions from fringing capacitance to parallel plate capacitance as the measurement parameter. This change increases the capacitance value and test sensitivity while the MEMS parallel plate structure remains relatively simple to fabricate, effectively resolving the contradiction
Solution Approach 2:
The MEMS parallel plate structure serves multiple functions: it provides the capacitance measurement mechanism, supports polyimide film integration for enhanced sensitivity, and enables on-chip pressure and temperature measurements. This multi-functionality improves test sensitivity without proportionally increasing device complexity
3Measurement precision
If polyimide film is integrated to enhance sensitivity, then test sensitivity increases, but manufacturing complexity increases
Solution Approach 1:
The patent integrates a polyimide thin film with the MEMS sensor structure. The thin film nature of the polyimide layer allows it to be incorporated into the manufacturing process without significantly complicating fabrication, while effectively enhancing test sensitivity through its humidity-responsive properties
Solution Approach 2:
The integration of polyimide film creates a composite structure that combines the mechanical stability of MEMS with the humidity sensitivity of polyimide. This composite approach enhances test sensitivity while the established compatibility of polyimide with standard MEMS processes keeps manufacturing complexity manageable
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 MEMS humidity sensor achieves higher test sensitivity and accurate humidity measurement by leveraging parallel plate capacitance and polyimide film integration, while also measuring on-chip pressure and temperature.
Implementation Method 1
humidity is derived from parallel plate capacitance, such that the MEMS humidity sensor has higher test sensitivity
Implementation Method 2
a polyimide film may be integrated with the MEMS humidity sensor to further increase test sensitivity
Data Source
AI summary
A micro-electro mechanical system (MEMS) humidity sensor includes a first substrate, a second substrate and a sensing structure. The second substrate is substantially parallel to the first substrate. The sensing structure is between the first substrate and the second substrate, and bonded to a portion of the first substrate and a portion of the second substrate, in which the second substrate includes a conductive layer facing the sensing structure, and a first space between the first substrate and the sensing structure is communicated with or isolated from outside, and a second space between the conductive layer and the sensing structure is communicated with an atmosphere, and the sensing structure, the second space and the conductive layer constitute a capacitor configured to measure permittivity of the atmosphere, and humidity of the atmosphere is derived from the permittivity of the atmosphere, pressure of the atmosphere and temperature.