Resonant Pressure Sensor Structure to Prevent Balloon Effect
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Solution Overview
Problem
Conventional resonant pressure sensors experience degraded linearity and measurement precision when high static pressures are applied due to the 'balloon effect', which affects the diaphragm's stress and sensitivity.
Innovation Solution
The resonant pressure sensor employs a pressure sensing unit with a substrate-separated portion and a cantilever structure, incorporating a first and second resonator made of single-crystal silicon with differing impurity concentrations and temperature coefficients, to mitigate substrate strain and maintain high linearity across varying static pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional diaphragm structure is used to measure pressure, then the sensor can detect pressure changes, but the linearity of input-output characteristics is degraded when high static pressure is applied due to the balloon effect
Solution Approach 1:
The substrate is divided into a fixed portion and a separated portion, creating a cantilever structure. This segmentation isolates the resonator from the deforming peripheral regions, preventing the balloon effect from affecting measurement linearity while maintaining pressure detection capability.
Solution Approach 2:
The resonator is extracted from the conventional diaphragm structure and placed on a substrate-separated portion. This separation removes the resonator from the region affected by peripheral deformation, eliminating the harmful balloon effect while preserving the pressure sensing function.
2Measurement precision
If a pressure reference chamber is disposed on one side of the diaphragm to measure absolute pressure, then absolute pressure measurement is enabled, but the device complexity increases
Solution Approach 1:
The substrate-separated portion serves multiple functions: it provides mechanical support, enables pressure transmission to the resonator, and acts as a reference chamber for absolute pressure measurement. This multi-functionality eliminates the need for separate reference chambers, reducing device complexity.
Solution Approach 2:
The support structure and pressure reference chamber are merged into a single integrated substrate structure. This combination simplifies the overall device architecture while maintaining both absolute pressure measurement capability and structural support functions.
3Stability of the object's composition
If the substrate is made rigid to maintain structural stability, then structural stability is improved, but strain mitigation capability is reduced
Solution Approach 1:
The substrate is segmented into fixed and separated portions, creating a cantilever structure. This segmentation allows the fixed portion to provide structural stability while the separated portion isolates the resonator from strain propagation, achieving both stability and strain mitigation.
Solution Approach 2:
The substrate-separated portion acts as an intermediary between the fixed substrate and the resonator. It transmits pressure changes to the resonator while mitigating harmful strains, serving as a buffer that protects the resonator from direct strain exposure.
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 configuration ensures high linearity and excellent measurement precision regardless of the magnitude of static pressure applied, preventing the balloon effect and enhancing accuracy.
Implementation Method 1
a first resonator 4 that is disposed in the substrate-separated portion 32 and has a resonance frequency that changes based on strain that arises according to static pressure applied to the substrate-separated portion 32 by a pressure-receiving fluid
Implementation Method 2
a resonance frequency that changes based on strain that arises according to static pressure applied to the substrate-separated portion 32 by a pressure-receiving fluid
Data Source
Figure 1A~1B
Figure 2
Figure 3~4
AI summary
A resonant pressure sensor (1A; 1B) includes: a housing (50); a housing-fixed portion (2) fixed to the housing; a substrate (3; 3A; 3B; 3C) including a substrate-fixed portion (31) fixed to the housing-fixed portion (2) and a substrate-separated portion (32; 32A; 32B; 32C)) separated from the housing-fixed portion (2) and extending from the substrate-fixed portion (31); a first resonator (4) disposed in the substrate-separated portion (32; 32A; 32B; 32C) and configured to detect a change of a resonance frequency based on a strain in the substrate (3; 3A; 3B; 3C) caused by static pressure applied by a pressure-receiving fluid (F; K); and a processor (1). The pressure-receiving fluid (F: K) is intended to be interposed in a gap defined between the housing-fixed portion (2) and the substrate (3; 3A; 3B; 3C) and envelop the substrate (3; 3A; 3B; 3C). The processor is configured to measure the static pressure based on the detected change of the resonance frequency. The first resonator (4) is made of a semiconductor material comprising an impurity. A concentration of the impurity is 1×1020 cm-3 or higher, and an atomic radius of the impurity is smaller than an atomic radius of the semiconductor material.