MEMS Pressure Sensor Structure for Minute Pressure Detection
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Solution Overview
Problem
Existing semiconductor pressure sensors require thinning of silicon wafers, making it difficult to integrate them with ICs and limiting their ability to accurately measure minute pressures.
Innovation Solution
A MEMS element with a flexible portion on a substrate, a fixation electrode, and a movable electrode, where external pressure causes bending that changes the resonator's vibration characteristics, allowing for precise pressure detection by analyzing frequency changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a strain sensing element is formed on a silicon wafer with thinning of the opposite surface, then pressure detection capability is achieved, but integration with semiconductor devices (IC) becomes difficult
Solution Approach 1:
The patent combines the pressure sensor elements (diaphragm, electrodes) with the semiconductor device (IC) into a single integrated structure. The IC is mounted directly on the substrate with the diaphragm, eliminating the need for separate assembly and achieving both pressure detection capability and easy integration.
Solution Approach 2:
The substrate serves multiple functions: it provides mechanical support for the diaphragm structure, serves as a mounting platform for the IC, and acts as the base for the entire pressure sensor assembly. This multi-functionality simplifies the overall device structure and facilitates integration.
2Measurement precision
If a thin diaphragm portion is formed to detect minute pressure, then detection sensitivity for low pressure is improved, but manufacturing complexity increases
Solution Approach 1:
The patent replaces complex mechanical thinning processes with a simpler approach where the diaphragm is formed by depositing thin films (first and second films) on the substrate. This film deposition method is more easily controlled and manufactured than mechanical thinning, while still achieving the required thinness for minute pressure detection.
Solution Approach 2:
The patent controls the thickness of the diaphragm by adjusting the deposition parameters of the thin films during manufacturing. By changing film thickness parameters, the diaphragm can be optimized for detecting specific pressure ranges, including minute pressures, without increasing manufacturing complexity.
3Measurement precision
If the flexible portion is made extremely thin for high sensitivity, then measurement precision for low pressure improves, but structural stability deteriorates
Solution Approach 1:
The patent creates a composite structure where the flexible portion consists of multiple layers (first film, second film, and substrate). This composite structure provides the necessary flexibility for detecting minute pressures while the layered construction and substrate support maintain structural stability and prevent excessive deformation.
Solution Approach 2:
The patent applies different properties to different parts of the structure: the flexible portion (first and second films) is made thin and flexible for pressure sensitivity, while the substrate and electrode structures provide rigidity and structural support. This local differentiation of mechanical properties allows the system to achieve both high sensitivity and structural stability.
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
Enables accurate detection of minute pressures with simplified manufacturing and integration with ICs, reducing environmental impact and manufacturing costs while preventing diaphragm deformation.
Implementation Method 1
bending is generated in the flexible portion by applying external pressure to the flexible portion
Implementation Method 2
a vibration characteristic of the resonator, that is, a resonant frequency is changed. By deriving a relationship between the external pressure and the change of the frequency characteristic of the resonator
Data Source
AI summary
A MEMS element includes a substrate which includes a flexible portion, a fixation electrode which is provided on a principal surface of the substrate, and a movable electrode which includes a movable portion which is separated from the fixation electrode, overlaps with at least a portion of the fixation electrode in a plan view of the principal surface, and is driven in a direction intersecting the principal surface, and a fixation end connected to the principal surface. The fixation electrode and the movable electrode is disposed to correspond to the flexible portion.