MEMS Hermeticity Detection via Capacitance-Offset Analysis
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Solution Overview
Problem
Current methods for determining the hermeticity of MEMS devices are difficult to perform and lack sensitivity, as they rely on measuring electronic characteristics like leakage current or frequency response associated with the Q-factor.
Innovation Solution
Applying multiple voltage differences between a movable part and a sensor electrode to measure effective capacitances, calculating the capacitance-to-voltage curve, and evaluating the symmetry by determining if the offset voltage is within a predetermined range to assess hermeticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hermeticity detection is performed by measuring leakage current or frequency response, then the detection can be performed, but the sensitivity and ease of operation are insufficient
Solution Approach 1:
The patent changes the measurement parameter from leakage current or frequency response to capacitance values at different voltage levels. By applying multiple voltage differences and measuring corresponding capacitances, the method transforms the detection approach to achieve higher sensitivity while maintaining operational simplicity through direct capacitance measurements.
Solution Approach 2:
The patent replaces the electrical measurement approach (leakage current) with a capacitive measurement approach. This substitution enables more sensitive detection of hermeticity status by measuring capacitance changes that occur when the MEMS device transitions between hermetic and non-hermetic states, providing clearer detection signals.
2Measurement precision
If multiple voltage differences are applied to measure capacitances, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent uses the existing sensor electrode and movable part structure for dual purposes: normal sensing operations and hermeticity detection. The same capacitive sensing mechanism serves both functional operations and diagnostic testing, eliminating the need for separate dedicated test structures and reducing overall device complexity.
Solution Approach 2:
The MEMS device performs self-diagnosis for hermeticity detection using its own operational components. By utilizing the inherent capacitance characteristics of the sensor electrode and movable part during normal operation, the device can autonomously detect its hermeticity status without requiring external specialized testing equipment or procedures.
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 method provides a more sensitive and accurate means of determining hermeticity, allowing for immediate and self-testing detection of MEMS device integrity with high sensitivity and accuracy.
Implementation Method 1
measuring a capacitance value between the sensor electrode and the movable part
Implementation Method 2
applying a first voltage difference and a second voltage difference between a first sensor electrode and a movable part
Data Source
AI summary
A method of detecting whether a microelectromechanical system (MEMS) device is hermetic includes applying at least three voltage differences between a movable part and a sensor electrode of the MEMS device to measure at least three effective capacitances, calculating a capacitance-to-voltage curve and an offset voltage of the MEMS device according to the at least three effective capacitances; and determining whether the offset voltage is within a predetermined range to determine whether MEMS device is hermetic.