Segmented Electrode Structure for Quadrature Error Reduction in MEMS Gyroscopes
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Solution Overview
Problem
MEMS angular rate sensors, such as gyroscope devices, face issues with quadrature error due to manufacturing imperfections, leading to offset errors, reduced dynamic range, and increased noise, which can result in device damage from electrode collisions.
Innovation Solution
A segmented electrode structure is integrated into the MEMS device, connected through routing layers to a switch structure and active circuit, allowing selective activation of electrode segments to apply electrostatic forces and compensate for quadrature motion and bonding misalignments, thereby reducing quadrature errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If manufacturing processes are simplified, then ease of manufacture improves, but quadrature error increases due to manufacturing imperfections
Solution Approach 1:
The electrode structure is divided into multiple independently controllable segments. Each segment can be selectively activated or deactivated to compensate for quadrature motion in different regions of the proof mass, allowing precise control over the electrostatic forces applied to correct manufacturing imperfections.
Solution Approach 2:
The system dynamically adjusts the voltage parameters applied to different electrode segments to modulate electrostatic forces. By changing voltage magnitudes and polarities across segmented electrodes, the system compensates for quadrature error without requiring tighter manufacturing tolerances.
2Measurement precision
If quadrature compensation is added, then measurement precision improves, but device complexity increases
Solution Approach 1:
The segmented electrode structure serves multiple functions: it provides both the primary drive function for proof mass oscillation and the quadrature compensation function. The same electrode segments that drive the proof mass can be selectively activated to compensate for quadrature error, eliminating the need for separate compensation electrodes and reducing overall device complexity.
Solution Approach 2:
The system dynamically switches between different electrode segment configurations to adapt to varying quadrature error conditions. Control circuitry selectively activates specific segments based on detected quadrature motion, allowing the device to maintain high measurement precision across different operating conditions without requiring a fixed complex compensation structure.
3Reliability
If electrode segments are selectively activated, then reliability improves by preventing collisions, but energy consumption increases
Solution Approach 1:
The control system periodically monitors proof mass position and selectively activates electrode segments only when quadrature motion is detected that would lead to collision risk. This periodic monitoring and selective activation prevents unnecessary energy consumption while maintaining reliability by intervening only when needed to prevent collisions.
Solution Approach 2:
The segmented electrode structure automatically compensates for quadrature motion and prevents collisions through feedback control without requiring external intervention. The system self-regulates by detecting quadrature error and activating appropriate segments, improving reliability while minimizing energy consumption through intelligent, need-based activation rather than continuous operation.
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 solution effectively reduces quadrature motion, enhances device accuracy, and prevents electrode collisions, improving the reliability and sensitivity of MEMS angular rate sensors.
Implementation Method 1
The electrode structure includes a plurality of electrode segments that can be selectively activated or deactivated to apply electrostatic forces to the movable mass of the MEMS device
Data Source
AI summary
An integrated device includes a MEMS device, such as a gyroscope, having a movable mass spaced apart from a substrate, the movable mass being configured to oscillate in a drive direction relative to the substrate. The integrated device further comprises an integrated circuit (IC) die having a surface coupled with the MEMS device such that the movable mass is interposed between the substrate and the surface of the IC die. An electrode structure is formed on the surface of the IC die, the electrode structure including a plurality of electrode segments vertically spaced apart from the movable mass. Openings extend through the movable mass and the electrode segments overlie the openings. Suitably selected electrode segments can be activated to electrostatically attract the movable mass toward sense electrodes vertically spaced apart from the MEMS to reduce quadrature motion of the movable mass.