Vertical Spring Stress Isolation in MEMS Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for stress isolation in MEMS devices are costly and can damage the devices during the release etching process, and may not effectively manage stress in the presence of pressure differences.
Innovation Solution
The use of three-dimensional trenches in the substrate to form vertical springs that provide stress isolation without a through etch, preventing interaction with etching gases and potential damage to the MEMS device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through etching is used to form vertical springs for stress isolation, then stress isolation is achieved, but the MEMS device may be damaged by etching gases
Solution Approach 1:
The patent divides the etching process into two separate non-through etches: one from the front surface and one from the back surface of the substrate. This segmentation prevents etching gases from reaching and damaging the MEMS device while still achieving complete stress isolation through the formation of vertical springs that extend through the substrate thickness without creating open pathways to the device
Solution Approach 2:
The patent introduces a sacrificial layer as an intermediary element between the etching process and the MEMS device. This sacrificial layer protects the device from direct exposure to etching gases while allowing the vertical spring structure to be formed. The sacrificial layer is subsequently removed to complete the stress isolation structure
2Reliability
If existing stress isolation methods are used, then some stress protection is provided, but the process is costly and complex
Solution Approach 1:
The patent combines multiple functions into the vertical spring structure: stress isolation, mechanical support, and stress compensation during pressure differences. By merging these functions into a single integrated structure formed through a unified fabrication process, the patent reduces overall process complexity and cost compared to using separate components for each function
Solution Approach 2:
The vertical spring structure serves multiple purposes: it provides stress isolation from the substrate, acts as a mechanical support for the MEMS device, and compensates for stress during pressure differences. This multi-functionality reduces the need for additional separate structures and processes, thereby reducing fabrication complexity and cost
3Reliability
If existing stress isolation methods are used, then some stress protection is provided, but device integrity cannot be ensured across varying pressure conditions
Solution Approach 1:
The patent designs the vertical spring structure with controlled mechanical properties that allow it to dynamically respond to pressure differences. The spring can compress or extend elastically in response to pressure changes, maintaining device integrity across varying pressure conditions while continuing to provide stress isolation from the substrate
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
This approach effectively isolates MEMS devices from package-induced stress without damaging them, reducing costs and ensuring device integrity across varying pressure conditions.
Implementation Method 1
A vertical spring is etched in the substrate about the device
Data Source
AI summary
In one example, a method comprises etching a vertical spring in a substrate, the vertical spring encompassing a device formed on a front side of the substrate. The method further comprises bonding a cap to the front side of the substrate, the cap disposed over the device and the vertical spring.