Semiconductor Microbalance With Molybdenum Electrodes
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Solution Overview
Problem
Existing microbalances, particularly those using quartz and silicon substrates, face challenges with sensitivity, complexity in manufacturing, and large dimensions, limiting their application in fields like food quality control and environmental monitoring.
Innovation Solution
A semiconductor-based microbalance with a buried cavity diaphragm, integrated electronic high-frequency circuit, and piezoelectric region, utilizing molybdenum electrodes and aluminum nitride for enhanced sensitivity and reduced dimensions, fabricated using microelectronic techniques.
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 dimensions increase
Solution Approach 1:
The patent changes the material parameter from quartz to piezoelectric material layers deposited on silicon substrates, and changes the operational frequency parameter to high-frequency range (1-10 GHz), thereby achieving high sensitivity while enabling compatibility with standard semiconductor manufacturing processes
Solution Approach 2:
The patent replaces the mechanical quartz resonator structure with an electro-acoustic resonator system using piezoelectric material layers between electrode layers, allowing integration with electronic circuits and semiconductor fabrication techniques while maintaining high detection sensitivity
2Measurement precision
If quartz sensors are used for chemical detection, then sensitivity is improved, but overall dimensions increase
Solution Approach 1:
The patent embeds the piezoelectric material layers and electrode structures within a silicon substrate platform, nesting the sensing function within the semiconductor device architecture, thereby reducing overall dimensions while maintaining sensitivity
Solution Approach 2:
By changing to high-frequency operation (1-10 GHz) and using thin piezoelectric material layers, the patent achieves high sensitivity with reduced physical dimensions compared to traditional quartz sensors operating at lower frequencies
3Ease of manufacture
If bulk micromachining is used to create sensor cavities, then manufacturing is simplified, but device dimensions increase
Solution Approach 1:
The patent extracts only the essential sensing function by creating localized piezoelectric material layers and electrode structures on the silicon substrate surface, rather than using bulk micromachining to create large cavities, thereby reducing device dimensions while maintaining manufacturability
Solution Approach 2:
The patent transitions from three-dimensional bulk micromachining cavities to two-dimensional surface-based piezoelectric material layer structures, achieving compact dimensions while preserving the resonant sensing function through high-frequency operation
4Productivity
If multiple sensors are integrated on a single chip, then productivity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent creates a universal platform using standard semiconductor manufacturing processes that can produce multiple identical piezoelectric resonator sensors on a single silicon wafer, achieving high integration density while maintaining consistent precision through process standardization
Solution Approach 2:
By operating at high frequencies (1-10 GHz) and using thin piezoelectric material layers, the patent reduces the critical dimensions that need to be controlled, thereby enabling multiple sensors per chip while maintaining achievable manufacturing precision with standard semiconductor fabrication techniques
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 semiconductor microbalance achieves high sensitivity and compact size, enabling integration of multiple sensors in a single chip with reduced manufacturing costs and improved performance for chemical detection applications.
Implementation Method 1
a piezoelectric material layer, arranged between two electrode layers, overlies a cavity and forms an acoustic resonator
Implementation Method 2
the resonator forms an integrated microbalance based upon the piezoelectric effect... the quartz forms, with an associated oscillating circuit, an electrical resonator having a natural resonance frequency
Data Source
AI summary
An electronic microbalance made in a semiconductor body accommodating an oscillating circuit adjacent to a diaphragm. A stack formed by a first electrode, a second electrode, and a piezoelectric region arranged between the first and the second electrode extends above the diaphragm. Any substance that deposits on the stack causes a change in the mass of the microbalance and thus in the resonance frequency of a resonator formed by the microbalance and by the oscillating circuit and can thus be detected electronically. A chemical sensor is obtained by forming a sensitive layer of a material suitable for binding to target chemicals on the stack. The sensitivity of the microbalance can be increased by making the first electrode of molybdenum so as to increase the piezoelectric characteristics of the piezoelectric region.