Micromechanical Motion Sensor Height Reduction via Wafer Orientation
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Solution Overview
Problem
Existing micromechanical motion sensors face challenges in reducing the height of sensor components while maintaining performance, as the sealing wafers increase the height and sensitivity to thermal stress and environmental disturbances.
Innovation Solution
A method for manufacturing micromechanical motion sensors by joining and dicing wafers to create components with a smaller area and height, where electrical connections are deposited on the largest dice cutting surface, and the seismic mass is designed as a long beam-like or triangular structure supported by thin springs, allowing for reduced height and increased performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sealing wafers are used to hermetically seal the wafer plane, then reliability is improved, but height of the sensor component increases
Solution Approach 1:
The patent changes the orientation of the seismic mass from a planar configuration to a three-dimensional configuration that utilizes the thickness direction of the wafer. The seismic mass is formed as a beam-like structure extending in the thickness direction, allowing the sensor to achieve its function with reduced lateral dimensions while maintaining acceptable height through the wafer stack.
Solution Approach 2:
The patent modifies the geometric parameters of the seismic mass, specifically designing it as a long beam-like structure with dimensions optimized for the thickness direction. This parameter change allows the seismic mass to achieve sufficient mass for inertia sensing while minimizing the lateral footprint, thereby reducing the overall component height when sealed between wafers.
2Length of stationary object
If sealing wafers are made thinner to reduce component height, then height is improved, but sensitivity to thermal stress and environmental disturbances increases
Solution Approach 1:
By orienting the seismic mass to extend primarily in the thickness direction rather than laterally, the patent enables the use of thinner sealing wafers. The seismic mass achieves its required mass through increased thickness rather than lateral expansion, allowing the sealing wafers to be thinner while maintaining structural integrity and reducing sensitivity to thermal stress.
Solution Approach 2:
The patent employs a composite structure where the seismic mass is formed from the wafer material itself (silicon) rather than being a separate component. This integration creates a composite structure where the wafer serves both as the structural support and as part of the sensing element, improving thermal matching and reducing sensitivity to thermal stress.
3Productivity
If the area of motion sensor component is reduced, then productivity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes the thickness dimension of the wafer to accommodate the seismic mass, allowing for larger effective sensing mass without increasing the lateral footprint. This enables more components to be diced from each wafer (improving productivity) while the three-dimensional structure of the seismic mass maintains the required mass properties without demanding excessive manufacturing precision in the lateral dimensions.
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 method results in significantly reduced component height, improved performance, and reduced sensitivity to thermal stress, enabling the use of micromechanical motion sensors in smaller form factors with enhanced reliability.
Implementation Method 1
the micro systems formed on the central wafer 1 are sealed by attaching two hermetically sealing wafers 2, 3 on the top and bottom sides of the wafer, by, for example, anodic bonding
Implementation Method 2
the measuring is based on, for example, the capacitive principle, wherein a change in the motional state of the sensor causes a displacement of a spring suspended seismic mass. The position of the mass can be detected by means of the capacitance between a pair of electrodes
Data Source
AI summary
The present invention relates to measuring devices used in measuring physical quantities, such as acceleration, angular acceleration, or angular velocity, and, more precisely, to micromechanical motion sensors. The area, in the wafer plane, of a motion sensor component according to the present invention is smaller than the area of the motion sensor component having been dice cut and turned by 90°. Correspondingly, the height of the motion sensor component according to the present invention, the component having been turned by 90°, is smaller, in the direction of the joint, than the thickness of the wafer stack formed by the joined wafers. The object of the invention is to provide an improved method of manufacturing a micromechanical motion sensor, and to provide a micromechanical motion sensor suitable, in particular, for use in small micromechanical motion sensor solutions.