MEMS Vibrating Beam Accelerometer Test Actuators for Wafer Screening
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Solution Overview
Problem
Existing MEMS vibrating beam accelerometers face challenges in accurately measuring proof mass motion during wafer-level probe testing due to the inability to induce motion, leading to delayed detection of failures such as broken flexures or stuck devices, and difficulties in measuring the quality factor (Q) associated with the proof mass natural frequency.
Innovation Solution
Incorporation of built-in test actuators within MEMS vibrating beam accelerometers allows for the measurement of proof mass motion at wafer-level probe testing, enabling early screening of failing devices and improving the characterization of the quality factor (Q) by using differential frequency measurements to reject common-mode errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wafer-level probe testing is performed without built-in test actuators, then manufacturing process remains simple, but inability to induce proof mass motion prevents early detection of failures
Solution Approach 1:
The built-in test actuators are integrated into the accelerometer structure during manufacturing, enabling preliminary testing actions to be performed at wafer-level probe testing before packaging. This allows proof mass motion to be induced and failures to be detected early in the manufacturing process, resolving the contradiction between early failure detection and device complexity.
2Productivity
If built-in test actuators are added to enable proof mass motion measurement, then early screening capability is improved, but device complexity increases
Solution Approach 1:
The test actuator electrodes are merged with the existing resonator electrode structures in the MEMS device. The same electrode patterns serve dual purposes: driving the resonators during normal operation and acting as test actuators to induce proof mass motion during screening. This merging approach enables early screening efficiency improvement while minimizing the increase in device complexity.
3Measurement precision
If traditional testing methods are used without proof mass motion induction, then testing process remains simple, but quality factor measurement accuracy deteriorates
Solution Approach 1:
The resonator structures themselves serve as the test objects, and the built-in test actuators enable the device to self-test its own performance characteristics. By inducing proof mass motion through the test actuators and measuring the resonator response, the system can accurately determine quality factor and other performance parameters without requiring external testing equipment, thereby improving measurement precision while keeping the testing structure relatively simple.
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 enhances the accuracy of accelerometer performance by enabling early detection of manufacturing defects and precise measurement of acceleration, reducing bias errors and improving repeatability through differential frequency analysis.
Implementation Method 1
The resonator may be electrically coupled to an oscillator, or other signal generation circuit, which causes the resonator to vibrate at its resonant frequency
Implementation Method 2
Accelerometers function by detecting a displacement of a proof mass under inertial forces
Data Source
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AI summary
An example system comprising: a microelectromechanical system (MEMS) vibrating beam accelerometer (VBA) comprising: a proof mass; and a first resonator mechanically coupled to the proof mass; a first electrode configured to apply a force to the proof mass.