Vacuum-Resistant Pressure Sensor With Isolated Diaphragm
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Pressure sensors using MEMS technology experience output shifts and accuracy issues when exposed to high vacuum and high temperature conditions, making it difficult to maintain accurate measurements.
Innovation Solution
A pressure sensing device with a support structure, isolated diaphragm, and low vapor pressure working oil, such as perfluoropolyether, that transfers pressure to a MEMS die sensing element within a sealed cavity, preventing outgassing and maintaining measurement accuracy in harsh environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional pressure sensors are used in high vacuum environments, then the device can be compact and accurate under normal conditions, but the measurement accuracy deteriorates due to output shift
Solution Approach 1:
The patent introduces a working fluid (oil or gas) as an intermediary medium between the diaphragm and the MEMS sensor. This working fluid transmits pressure forces from the diaphragm to the sensor while being contained in a sealed cavity, preventing direct exposure of the sensor to vacuum conditions and eliminating the output shift problem
Solution Approach 2:
The pressure sensing device is divided into separate functional zones: a vacuum-sealed cavity containing the MEMS sensor and working fluid, and an external region for pressure application. The diaphragm separates these zones, allowing independent optimization of each region's conditions without affecting the other
2Force
If the sealed cavity is filled with conventional oil, then pressure transfer is achieved, but outgassing occurs in high vacuum conditions causing measurement drift
Solution Approach 1:
The patent specifies selecting working fluids with particular physical parameters - specifically low vapor pressure and low volatility - to minimize outgassing. The working fluid's chemical composition and physical properties are optimized for vacuum compatibility while maintaining effective pressure transmission
Solution Approach 2:
The sealed cavity creates an inert environment isolated from the external vacuum. The working fluid inside the cavity acts as a stable, non-outgassing medium that maintains pressure transmission without degrading the vacuum environment, effectively creating a protective barrier
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 device maintains measurement sensitivity and accuracy within a designated tolerance range even at extreme conditions like 0.001 Pa pressure and 90°C temperature, enabling its use in harsh applications like semiconductor manufacturing.
Implementation Method 1
A pressure exerted on the outer side of the isolated diaphragm by a fluid medium is transferred via the working oil to the MEMS die sensing element to measure the pressure of the fluid medium
Implementation Method 2
The working oil has a low vapor pressure and a low volatility content to avoid (or at least reduce the extent of) outgassing of the working oil (e.g., releasing vapor bubbles) in high vacuum and high temperature conditions
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A pressure sensing device includes a support structure 105, an isolated diaphragm 104, a working oil 126, and a MEMS die sensing element 102. The support structure 105 defines a portion of a sealed cavity 124. The isolated diaphragm 104 is mounted to the support structure 105. The isolated diaphragm 104 has in inner side 134 that defines an end of the sealed cavity 124 and an outer side 136 opposite the inner side 134. The working oil 126 is contained within the sealed cavity 124. The MEMS die sensing element 102 is enclosed within the support structure 105. The MEMS die sensing element 102 is exposed to the working oil 126 within the sealed cavity 124. A pressure exerted on the outer side 136 of the isolated diaphragm 104 by a fluid medium is transferred via the working oil 126 to the MEMS die sensing element 102 to measure the pressure of the fluid medium.