MEMS Bilayer Stopper Mitigating Charge-Induced Stiction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS packages face issues with stiction due to oxide stoppers accumulating charges and having high surface energy, leading to reliability and operational problems during fabrication and operation.
Innovation Solution
The use of bilayer stoppers with a conductive layer and an underlying insulating layer, where the conductive layer serves as a buffer and reduces charge accumulation and surface energy, and additional stoppers are placed to enhance structural strength and withstand colliding forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxide stoppers are used to prevent movable element overextension, then the stoppers can stop or mitigate stiction during shock events, but the oxide stoppers accumulate charges and have high surface energy leading to charge-induced and Van Der Waals stiction
Solution Approach 1:
The patent applies composite materials by combining a soft material layer (first material) and a hard material layer (second material) in a bilayer stopper structure. The soft material layer has low surface energy and does not accumulate charges, while the hard material layer provides structural strength. This composite structure resolves the contradiction by eliminating charge accumulation and low surface energy issues of oxide stoppers while maintaining stopper functionality.
Solution Approach 2:
The patent changes the material parameters of the stopper by selecting materials with specific properties: the soft material layer is chosen for its low surface energy and charge-free characteristics, while the hard material layer is selected for its high strength. This parameter change approach transforms the stopper from a single-material oxide structure to a multi-material structure with optimized properties that prevent stiction without generating harmful effects.
2Ease of manufacture
If a single-layer stopper structure is used, then the manufacturing process is simpler, but the stopper lacks sufficient structural strength to withstand colliding forces
Solution Approach 1:
The patent uses composite materials with a soft material layer deposited first followed by a hard material layer. The soft layer provides a base structure that is easier to form, while the hard layer adds the necessary strength to withstand colliding forces. This layered composite approach maintains relative manufacturing simplicity while significantly improving strength compared to a single-layer structure.
Solution Approach 2:
The patent segments the stopper into two distinct functional layers: a soft material layer for ease of formation and a hard material layer for strength. This segmentation allows each layer to be optimized for its specific function while maintaining a relatively simple overall manufacturing process using sequential deposition techniques.
3Reliability
If the contact area between stopper and movable element is increased, then the stiction mitigation during shock events is improved, but the surface energy and charge accumulation effects are amplified
Solution Approach 1:
The patent applies composite materials where the soft material layer has low surface energy and does not accumulate charges, allowing for increased contact area without amplifying harmful effects. The hard material layer provides structural support. This composite structure enables larger contact area for better shock mitigation while the inherent properties of the soft material prevent charge accumulation and reduce Van Der Waals forces.
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 bilayer stoppers improve the reliability and strength of the MEMS package by mitigating charge-induced and Van Der Waals stiction, while additional stoppers enhance the structural integrity, resulting in improved operational reliability and reduced stiction risks.
Implementation Method 1
the conductive layer serves as a buffer and reduces charge accumulation
Implementation Method 2
mitigating charge-induced and Van Der Waals stiction
Data Source
AI summary
Microelectromechanical systems (MEMS) packages and methods for forming the same are provided. The MEMS package includes a semiconductor substrate having a metallization layer over the semiconductor substrate. The MEMS package also includes a first planarization layer and an overlying second planarization layer over the metallization layer. The planarization structure has a first cavity therein exposing the metallization layer. The MEMS package also includes a MEMS device structure bonded to the second planarization layer. The MEMS device structure includes a moveable element over the first cavity. The MEMS package also includes a first stopper placed on the exposed metallization layer in the first cavity. The first stopper includes a patterned conductive layer and an underlying patterned insulating layer.