MEMS Vertical Stops and Anchor Structures for Stiction Control
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Solution Overview
Problem
The manufacture of Micro-Electro-Mechanical Systems (MEMS) devices is complex and costly due to the need for strong anchors to support moving elements, which must withstand measurement-induced stresses, and the risk of stiction between moving masses and the semiconductor substrate, leading to reliability and performance issues.
Innovation Solution
The introduction of stops in MEMS devices, formed by growing a device layer with recessed regions and anchor structures, helps to reduce stiction and enhance reliability by limiting the movement of moving masses and preventing contact with the semiconductor substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stops are added to the moving mass to reduce stiction, then reliability is improved, but device complexity increases
Solution Approach 1:
The stop structure is merged with the moving mass as an integrated feature rather than a separate component. The stop is formed as part of the moving mass structure, allowing it to limit movement and prevent stiction without adding independent structural elements that would increase device complexity.
Solution Approach 2:
The moving mass is segmented into functional regions including the stop portion and the main moving element. This segmentation allows the stop to be positioned at specific locations where it is most effective in preventing stiction, while the rest of the moving mass maintains its measurement functionality.
2Strength
If anchors are made stronger to support moving elements, then structural integrity is improved, but manufacturing complexity increases
Solution Approach 1:
The anchor structure is designed with varying thickness and material properties at different locations. The anchor is thicker and stronger at the base where it attaches to the substrate, and tapers or thins toward the moving element. This local variation in quality provides the necessary strength without requiring uniform thickening throughout, simplifying manufacturing.
Solution Approach 2:
The anchor may utilize composite material structures combining different materials with complementary properties. This allows the anchor to achieve high strength-to-weight ratio and excellent mechanical properties while using standard semiconductor manufacturing processes, avoiding complex multi-step fabrication.
3Measurement precision
If the spacing between moving mass and substrate is reduced to improve measurement range, then measurement precision is improved, but risk of stiction increases
Solution Approach 1:
The stop structure is positioned in advance to preemptively prevent stiction before it occurs. By placing the stop at the critical spacing point, it creates a mechanical barrier that prevents the moving mass from contacting the substrate, thereby eliminating stiction risk while maintaining small spacing for improved measurement range.
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 implementation of stops in MEMS devices improves reliability and performance by reducing stiction and enhancing the structural integrity of the moving elements, while also simplifying the manufacturing process.
Implementation Method 1
forming a device layer overlying the intermediate layer... wherein the device layer is configured to fill the one or more recessed regions that form the one or more stops
Data Source
AI summary
A semiconductor device is disclosed having one or more stops that is configured to limit movement of a moving mass. The one or more stops are formed in or on the semiconductor substrate. The one or more stops are attached to the moving mass. An intermediate layer is formed overlying the semiconductor substrate. A device layer is formed overlying the intermediate layer. The device layer, the intermediate layer, and the semiconductor substrate are single crystal. The moving mass is formed in the device layer with the one or more stops. The one or more stops comprises the material of the device layer. The moving mass couples to at least one anchor. Portions of the intermediate layer are removed to free the moving mass in relation to the semiconductor substrate.