MEMS Transducer Integrating Capacitive Humidity Sensor and Microphone
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Solution Overview
Problem
The integration of additional sensors in mobile devices is limited by physical size and increased cost, necessitating innovative solutions for adding functionality without significant space or cost increments.
Innovation Solution
A microelectromechanical systems (MEMS) transducer is developed, integrating a capacitive MEMS humidity sensor with a microphone on the same semiconductor die, using a substrate with a cavity and perforated electrode plates separated by a gas-sensitive material, allowing for simultaneous fabrication and increased device functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional sensors are integrated in mobile devices, then functionality is improved, but device size and cost increase
Solution Approach 1:
The patent combines a humidity sensor and a microphone into a single integrated MEMS device structure. The humidity sensor utilizes the same capacitive plate structure as the microphone, with the gas-sensitive material filling the cavity between the plates. This merging allows both sensors to share common components including the substrate, electrode plates, and packaging structure, thereby adding functionality without proportionally increasing device size.
Solution Approach 2:
The capacitive plate structure serves dual functions: it acts as both the sensing element for the microphone (detecting sound pressure waves) and the electrode for the humidity sensor (detecting gas concentration). The cavity space is universally utilized for both acoustic wave transmission and gas-sensitive material placement, enabling one structural element to support multiple sensing functions simultaneously.
2Adaptability or versatility
If additional sensors are integrated in mobile devices, then functionality is improved, but fabrication complexity and cost increase
Solution Approach 1:
The patent merges the fabrication processes of the humidity sensor and microphone into a single integrated manufacturing flow. Both sensors are formed using the same sequence of steps including substrate preparation, electrode plate deposition, cavity formation, and sealing. This unified approach eliminates the need for separate fabrication lines and reduces overall manufacturing complexity compared to producing discrete sensors.
Solution Approach 2:
The patent utilizes parameter changes in the gas-sensitive material's electrical properties in response to humidity variations. The material's dielectric constant or resistance changes predictably with moisture concentration, enabling the sensor to detect humidity levels through electrical measurement. This physical parameter change provides a direct transduction mechanism that simplifies the sensing mechanism compared to mechanical or optical alternatives.
3Measurement precision
If gas sensitive material is placed in the spacing region, then humidity sensing capability is improved, but device complexity increases
Solution Approach 1:
The spacing region between the capacitive plates, which is already a necessary structural component for the microphone function, is simultaneously utilized as the housing for the gas-sensitive material. This universal use of the inter-plate space eliminates the need for separate sensor chambers or additional structural elements, thereby enhancing humidity sensing capability without proportionally increasing device complexity.
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 integration provides enhanced functionality with a small device size and simple fabrication, enabling multiple sensor types like humidity and acoustic sensors within a single package, reducing fabrication complexity and cost while offering improved performance.
Implementation Method 1
a gas sensitive material in the spacing region between the perforated first electrode plate and the second electrode plate. The gas sensitive material has an electrical property that is dependent on a concentration of a target gas.
Implementation Method 2
the membrane and backplate are made out of conductive materials and form 'plates' of a capacitor. Thus, as the distance separating the membrane and backplate changes in response to the incident sound wave, the capacitance changes between the 'plate' and an electrical signal is generated.
Data Source
AI summary
According to an embodiment, a microelectromechanical systems (MEMS) transducer includes a substrate with a first cavity that passes through the substrate from a backside of the substrate. The MEMS transducer also includes a perforated first electrode plate overlying the first cavity on a topside of the substrate, a second electrode plate overlying the first cavity on the topside of the substrate and spaced apart from the perforated first electrode plate by a spacing region, and a gas sensitive material in the spacing region between the perforated first electrode plate and the second electrode plate. The gas sensitive material has an electrical property that is dependent on a concentration of a target gas.