Rough Polysilicon Layer Reduces MEMS Stiction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS devices face stiction issues due to capillary, molecular van der Waals, and electrostatic forces, which can lead to reduced sensitivity and reliability, as the existing methods to mitigate stiction, such as reducing movable element size or increasing spring stiffness, compromise device sensitivity.
Innovation Solution
A polysilicon layer with a rough surface is deposited on the movable element and surrounding structures to reduce contact area and stiction forces, preventing sticking and allowing for softer springs to maintain sensitivity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the movable element size is reduced to prevent stiction, then stiction forces are reduced, but device sensitivity is compromised
Solution Approach 1:
The patent applies a rough surface coating specifically to the movable element's surface, creating local structural variation that reduces stiction forces without changing the overall device geometry or sensitivity characteristics. This localized modification allows the movable element to maintain its size while reducing harmful adhesion forces.
Solution Approach 2:
The patent modifies the surface parameters of the movable element by introducing a rough surface structure with specific topography. This parameter change in surface characteristics reduces the contact area and stiction forces while preserving the functional parameters of the device such as sensitivity and mechanical properties.
2Reliability
If spring stiffness is increased to prevent sticking, then reliability is improved, but device sensitivity is reduced
Solution Approach 1:
Instead of globally increasing spring stiffness, the patent applies a localized rough surface treatment to the movable element that specifically addresses stiction at the contact interface. This allows the springs to maintain their original, softer stiffness settings while still preventing sticking through reduced adhesion forces at the surface level.
3Ease of manufacture
If a smooth surface is used on the movable element, then manufacturing is easier, but stiction forces increase
Solution Approach 1:
The patent deliberately changes the surface parameter from smooth to rough by applying a specific coating or treatment process. Although this adds a manufacturing step, it dramatically reduces stiction forces by minimizing contact area and adhesion, making the overall device more reliable and functional.
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 polysilicon layer effectively reduces stiction forces, enhancing the reliability and sensitivity of MEMS devices by preventing sticking between movable elements and substrates or other components, while allowing for softer springs that improve device performance.
Implementation Method 1
A polysilicon layer with a rough surface is deposited on the semiconductor substrate
Implementation Method 2
MEMS devices face stiction issues due to capillary, molecular van der Waals, and electrostatic forces
Implementation Method 3
MEMS devices face stiction issues due to capillary, molecular van der Waals, and electrostatic forces
Data Source
AI summary
Embodiments of mechanisms for forming a micro-electro mechanical system (MEMS) device are provided. The MEMS device includes a substrate and a MEMS substrate disposed on the substrate. The MEMS substrate includes a movable element, a fixed element and at least a spring connected to the movable element and the fixed element. The MEMS device also includes a polysilicon layer on the movable element.