Silicon Piezoelectric Microbalance Sensor for Odor Detection
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Solution Overview
Problem
Existing integrated chemical sensors face challenges with sensitivity, complexity, and large dimensions, making them unsuitable for wide applications, particularly in the food, cosmetics, pharmaceutical, and automotive sectors, where they are needed for detecting volatile substances and chemical species.
Innovation Solution
A cartridge-like chemical sensor structure is developed, integrating microbalance cells on a semiconductor chip with a buried cavity and piezoelectric region, using a manufacturing process that reduces bulk and cost, enabling high sensitivity and compact dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quartz sensors are used for chemical detection, then sensitivity is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the material parameter from quartz to silicon, enabling the use of standard semiconductor manufacturing processes while maintaining the microbalance sensing mechanism. This material substitution resolves the contradiction by allowing high sensitivity through piezoelectric effects while achieving manufacturing simplicity through established silicon fabrication techniques
Solution Approach 2:
The patent copies the successful microbalance design from quartz to silicon substrates, adapting the proven sensing mechanism to a more manufacturable platform. This copying approach preserves the sensitivity characteristics while enabling scalable production through standard semiconductor industry processes
2Ease of manufacture
If bulk micromachining is used to create sensor cavities, then manufacturing is simplified, but sensor dimensions become large
Solution Approach 1:
The patent employs thin film deposition techniques to create the piezoelectric aluminum nitride layer and electrode structures, enabling miniaturization of the sensor cavity. This thin film approach allows the cavity to be formed within a compact volume while maintaining structural integrity and sensing performance, resolving the contradiction between ease of manufacture and compact dimensions
Solution Approach 2:
The patent transitions from bulk three-dimensional micromachining to thin-film layer-by-layer construction, effectively moving the manufacturing process to a two-dimensional deposition approach. This dimensional change enables precise control over cavity size and sensor thickness, achieving compact dimensions while maintaining manufacturing simplicity through standard thin film processes
3Ease of manufacture
If standard semiconductor processes are used, then manufacturing cost is reduced, but sensor sensitivity decreases
Solution Approach 1:
The patent creates a composite structure using aluminum nitride piezoelectric material combined with aluminum electrode layers on silicon substrate. This composite material approach enables the use of standard semiconductor manufacturing processes while achieving the piezoelectric properties necessary for high sensitivity detection, thus resolving the contradiction between cost reduction and sensitivity maintenance
Solution Approach 2:
The patent replaces mechanical quartz crystal structures with an electro-acoustic system using thin film piezoelectric layers and interdigitated electrodes. This substitution enables the use of standard semiconductor fabrication processes while maintaining the acoustic resonance mechanism for sensitive detection, achieving both cost reduction and sensitivity preservation
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 sensor achieves improved sensitivity and reduced dimensions, allowing for broader applications, including environmental monitoring, food quality control, and automotive air quality assessment, with a cost-effective and compact design.
Implementation Method 1
integrated sensors using piezoelectric layers for detecting acoustic waves have been studied, wherein a piezoelectric material layer, arranged between two electrode layers, overlies a cavity and forms an acoustic resonator
Implementation Method 2
These electro-acoustic resonators have been proposed for manufacturing sensors of different types, such as force, pressure, acceleration, weight, and chemicals detecting sensors, which exploit the variation of the oscillating frequency of the acoustic resonator following a variation of its mass
Data Source
AI summary
A cartridge-like chemical sensor is formed by a housing having a base and a cover fixed to the base and provided with an input opening, an output hole and a channel for a gas to be analyzed. The channel extends in the cover between the input opening and the output hole and faces a printed circuit board carrying an integrated circuit having a sensitive region open toward the channel and of a material capable to bind with target chemicals in the gas to be analyzed. A fan is arranged in the housing, downstream of the integrated device, for sucking the gas after being analyzed, and is part of a thermal control system for the integrated circuit.