MEMS Sensor Mass Tuning via Embedded Metal Wells
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Solution Overview
Problem
Conventional methods for increasing the mass of MEMS sensor elements, such as thickening silicon layers, enlarging the die, or depositing substances on top, face challenges like fabrication errors, increased cost, stress sensitivity, and misalignment of the center of mass, which affect the accuracy and stability of MEMS devices.
Innovation Solution
Embedding tungsten or tantalum-filled wells into the surface of silicon-based MEMS sensor elements to increase their effective mass without inducing stress, allowing for precise fabrication and improved signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If silicon layers are thickened to increase mass, then the mass of MEMS sensor elements increases, but fabrication errors increase and manufacturing precision deteriorates
Solution Approach 1:
The patent divides the mass increase function into two independent parts: the silicon sensor element structure and the added mass component. The heavy metal wells are segmented and embedded within the silicon structure, allowing each to be optimized independently - the silicon for fabrication precision and the metal for mass increase.
Solution Approach 2:
The patent creates a composite structure combining silicon (for precise fabrication and sensor functionality) with heavy metals like tungsten or tantalum (for mass increase). This composite approach allows each material to contribute its superior properties without compromising the other.
2Weight of moving object
If the die size is enlarged to increase mass, then the mass of MEMS sensor elements increases, but device complexity and manufacturing cost increase
Solution Approach 1:
Instead of uniformly enlarging the entire die, the patent applies local quality enhancement by embedding heavy metal wells only in specific locations where mass increase is needed. This localized approach increases mass without proportionally increasing overall device complexity.
Solution Approach 2:
The patent changes the density parameter of the sensor element by introducing high-density metal materials (tungsten, tantalum) into the structure. This allows mass increase through material property modification rather than geometric scaling, avoiding the complexity associated with larger die sizes.
3Weight of moving object
If substances are deposited on top of the sensor element to increase mass, then the mass increases, but stress is induced and stability deteriorates
Solution Approach 1:
The patent embeds the heavy metal wells inside the silicon sensor element structure, nesting the mass-increasing component within the structural framework. This internal placement allows the metal to contribute to mass without being deposited on the external surface, thereby avoiding stress induction and maintaining structural stability.
4Weight of moving object
If conventional methods are used to increase mass, then the mass increases, but the center of mass becomes misaligned and measurement precision deteriorates
Solution Approach 1:
The patent performs preliminary positioning of the heavy metal wells during the fabrication process, placing them at predetermined locations that ensure proper center of mass alignment before the sensor element is completed. This preliminary action prevents misalignment issues that would otherwise require costly post-fabrication adjustments.
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 approach enhances the signal output and reduces Brownian noise by increasing the mass of MEMS sensor elements, improving their stability and accuracy while maintaining precise micro-machining capabilities and avoiding stress-related issues.
Implementation Method 1
Each well is filled with at least one metal so as to increase the effective mass of the movable MEMS sensor element
Data Source
AI summary
In one aspect, the disclosure is directed to a MEMS device. The MEMS device includes a silicon-based movable MEMS sensor element. The MEMS device also includes a plurality of wells formed into at least one surface of the movable MEMS sensor element. Each well is filled with at least one metal so as to increase the effective mass of the movable MEMS sensor element. The metal may be tungsten or tantalum, or an alloy with tungsten or tantalum.