Micromechanical Moisture Sensor with Substrate Trenches
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Solution Overview
Problem
Current micromechanical moisture and pressure sensors, when integrated into a single substrate, face challenges in enhancing moisture sensitivity and simplifying packaging and evaluation due to shared media access requirements, leading to suboptimal performance and increased costs.
Innovation Solution
Extending the moisture-sensitive polymer layer into the substrate trenches or wells surrounding the interdigital printed conductor tracks, allowing for increased capacitance and sensitivity, and integrating both sensor types on a shared substrate for synergy in signal evaluation and manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the moisture-sensitive polymer layer is extended into substrate trenches or wells, then moisture sensitivity is enhanced, but device complexity increases
Solution Approach 1:
The moisture-sensitive polymer layer is extended from the surface into the substrate depth by forming trenches or wells, utilizing the third dimension (depth) to increase the interaction area between the polymer layer and moisture, thereby enhancing sensitivity without increasing lateral footprint
Solution Approach 2:
The moisture-sensitive polymer layer is nested within the substrate structure by forming trenches or wells that are filled with the polymer material, creating a nested configuration where the sensing layer is embedded within the substrate, increasing sensitivity while maintaining compact device geometry
2Ease of manufacture
If both moisture sensor and pressure sensor are integrated in the same substrate, then manufacturing cost is reduced, but packaging complexity increases
Solution Approach 1:
The moisture sensor and pressure sensor are merged into a single substrate, with both sensor structures fabricated using integrated processes that share common steps such as substrate preparation, trench formation, and polymer layer deposition, thereby reducing manufacturing cost through consolidation
Solution Approach 2:
The substrate serves multiple functions by accommodating both the moisture sensor structure (with trenches filled with moisture-sensitive polymer) and the pressure sensor structure (with diaphragm and piezoresistive elements), creating a multi-functional integrated sensor device
3Measurement precision
If the moisture-sensitive polymer layer is extended into the substrate, then capacitance is increased, but manufacturing precision requirements increase
Solution Approach 1:
The trenches or wells are pre-formed in the substrate before depositing the moisture-sensitive polymer layer, providing predefined structures that guide the polymer deposition process and ensure consistent capacitance values across devices
Solution Approach 2:
The capacitance is increased by changing the geometric parameters of the polymer layer, specifically by extending it into the substrate depth through trenches or wells, thereby increasing the volume and surface area of the capacitive sensing element
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 enhances moisture sensitivity, simplifies packaging, and offers significant cost advantages by enabling a single package and combined evaluation unit for both sensors, while minimizing direct mechanical and thermal interactions with the pressure sensor.
Implementation Method 1
Using a capacitance measurement, it is possible to determine the moisture content of moisture-sensitive polymer layer 10
Implementation Method 2
the moisture-sensitive polymer layer extends into trenches in the substrate situated in the gaps of the interdigital printed conductor track arrangement
Data Source
AI summary
A micromechanical moisture sensor device includes: a substrate having a front side and a rear side; an interdigital printed conductor track arrangement provided above and/or below the front side of the substrate; and a moisture-sensitive polymer layer situated above and in the gaps of the interdigital printed conductor track arrangement. The moisture-sensitive polymer layer extends below the front side into the substrate.