MEMS Pressure Sensor Test Cell Sensitivity Estimation
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Solution Overview
Problem
The calibration of microelectromechanical systems (MEMS) pressure sensors is costly and prone to errors due to process variations affecting diaphragm width, requiring individual calibration with physical pressure stimuli.
Innovation Solution
A pressure sensor with multiple cells of differing sensitivities, where test cells with wider diaphragms are used to estimate the sensitivity of sense cells, allowing calibration without physical stimuli, reducing costs and improving process control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual calibration with physical pressure stimulus is performed, then measurement precision is improved, but manufacturing cost increases and calibration time increases
Solution Approach 1:
The pressure sensor is divided into multiple independent pressure cells on a single die, where at least one cell serves as a test cell with known sensitivity and others as sense cells. This segmentation allows the test cell to provide sensitivity information that can be used to calibrate sense cells without individual physical calibration, reducing manufacturing costs while maintaining measurement precision.
Solution Approach 2:
The test cell within the sensor array performs self-calibration by providing sensitivity information that automatically calibrates the sense cells. This self-service mechanism eliminates the need for external calibration equipment and physical pressure stimuli, reducing both cost and time while maintaining precision through the test cell's known sensitivity characteristics.
2Measurement precision
If individual calibration with physical pressure stimulus is performed, then measurement precision is improved, but calibration time increases
Solution Approach 1:
The test cell is pre-configured during manufacturing with known sensitivity characteristics and wider diaphragm dimensions. This preliminary action establishes a reference sensitivity that can be used to calibrate sense cells without requiring time-consuming physical pressure stimuli during operation, thereby reducing calibration time while maintaining measurement precision.
Solution Approach 2:
The test cell performs automatic self-calibration of sense cells by providing sensitivity information based on its known characteristics. This self-service calibration occurs without external intervention or physical pressure application, dramatically reducing calibration time while maintaining precision through the established sensitivity relationship between test and sense cells.
3Measurement precision
If test cells with wider diaphragms are used, then sensitivity estimation accuracy is improved, but device complexity increases
Solution Approach 1:
The test cell serves multiple functions: it acts as both a pressure sensing element and a calibration reference for sense cells. By making the test cell multi-functional, the patent reduces device complexity compared to having separate calibration equipment, while maintaining sensitivity estimation accuracy through the test cell's wider diaphragm and known sensitivity characteristics.
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 approach enables cost-effective sensitivity estimation and calibration of MEMS pressure sensors, reducing errors and improving feedback for process control without the need for physical stimulus calibration.
Implementation Method 1
Capacitive-sensing MEMS devices designs are highly desirable for operation in miniaturized devices due to their low temperature sensitivity, small size, and suitability for low cost mass production
Data Source
AI summary
A pressure sensor (20) includes a test cell (32) and sense cell (34). The sense cell (34) includes an electrode (42) formed on a substrate (30) and a sense diaphragm (68) spaced apart from the electrode (42) to produce a sense cavity (64). The test cell (32) includes an electrode (40) formed on the substrate (30) and a test diaphragm (70) spaced apart from the electrode (40) to produce a test cavity (66). Both of the cells (32, 34) are sensitive to pressure (36). However, a critical dimension (76) of the sense diaphragm (68) is less than a critical dimension (80) of the test diaphragm (70) so that the test cell (32) has greater sensitivity (142) to pressure (36) than the sense cell (34). Parameters (100) measured at the test cell (32) are utilized to estimate a sensitivity (138) of the sense cell (34).