MEMS Cap Structure With Eutectic Dimples Against Stiction
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Solution Overview
Problem
MEMS devices face issues with stiction, where movable elements adhere to the cap structure during movement, potentially damaging the device due to lack of surface roughness, leading to reduced reliability and increased manufacturing costs.
Innovation Solution
Formation of anti-stiction dimples on the movable elements using a eutectic material during the bond ring process, which increases surface roughness and reduces the likelihood of adhesion, combined with a single process step to form both the bond ring and dimples, simplifying manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the movable element has a smooth surface, then the manufacturing process is simpler, but the movable element adheres to the cap structure causing stiction and device damage
Solution Approach 1:
The patent applies local quality by creating dimples only in specific locations on the movable element surface rather than modifying the entire surface. These localized dimples provide the necessary anti-stiction functionality while maintaining simplicity elsewhere in the structure, thus improving reliability without excessive complexity
Solution Approach 2:
The patent uses spherical or curved dimples on the movable element surface. This curvature creates a non-sticking surface geometry that prevents adhesion to the cap structure. The spherical shape is effective at reducing stiction while being relatively simple to manufacture, addressing both reliability and complexity concerns
2Ease of manufacture
If separate processes are used to form the bond ring and anti-stiction features, then the manufacturing precision is higher, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent merges the formation of the bond ring and anti-stiction dimples into a single etching process step. By combining these two features that were previously made separately, the manufacturing process becomes simpler and less costly, while the single-step approach actually maintains adequate precision for both features
Solution Approach 2:
The etching process is designed to perform multiple functions simultaneously: it creates both the bond ring structure and the anti-stiction dimples in one operation. This multi-functionality reduces the total number of process steps and simplifies manufacturing without sacrificing the quality of either feature
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 anti-stiction dimples effectively prevent adhesion of movable elements to the cap structure, enhancing device reliability and reducing manufacturing complexity and costs while maintaining high throughput.
Implementation Method 1
an etch process for forming the bond ring is controlled so that eutectic material redeposits on the upper surfaces of the movable elements to form the dimples
Data Source
AI summary
In some embodiments, a semiconductor device is provided. The semiconductor device includes a semiconductor layer, a micro-electromechanical systems (MEMS) structure defined in the semiconductor layer, a bond ring over the semiconductor layer, and a cap structure over the MEMS structure and bonded to the bond ring. The MEMS structure has an upper surface and the cap structure has a lower surface facing the upper surface of the MEMS structure. Dimples of eutectic material are on the upper surface of the MEMS structure.