MEMS Protrusion Fabrication with Corner Lithography for Bending Resistance
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Solution Overview
Problem
Existing MEMS devices with oblong protrusions are vulnerable to bending or breaking, affecting their performance and functionality.
Innovation Solution
A method is developed to create a protrusion with a broad base and a shorter, oblong section using a monocrystalline wafer substrate, involving corner lithography and the use of silicon nitride and silicon oxide layers to form a pyramidal recess, followed by selective etching and deposition of filler material to enhance mechanical strength and reduce vulnerability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a long oblong protrusion is created in MEMS devices, then the protrusion can reach deeper into samples or perform specific functions, but the protrusion becomes vulnerable to bending or breaking
Solution Approach 1:
The protrusion is segmented into two distinct sections: an upper section with a first radius and a lower section with a second radius. This segmentation allows the lower section to be shorter and less vulnerable while the upper section provides the necessary length for sample interaction, effectively resolving the contradiction between length and reliability.
Solution Approach 2:
Different sections of the protrusion are given different local qualities through varying radii. The lower section has a smaller radius (higher curvature) making it more robust, while the upper section has a larger radius providing the needed length. This local differentiation allows each section to optimize for its specific function, resolving the length-vulnerability contradiction.
2Strength
If a broad base is provided for the protrusion, then mechanical strength is improved, but the protrusion length may be reduced
Solution Approach 1:
The protrusion is divided into upper and lower sections with different radii. The lower section provides a broad base with smaller radius for strength, while the upper section extends the length with larger radius. This segmentation allows both strength and length requirements to be satisfied simultaneously.
Solution Approach 2:
The solution transitions from a uniform cylindrical protrusion to a segmented structure with varying radius along its length. This dimensional variation along the protrusion axis allows the base to be broad (for strength) while the overall length is maintained or extended, resolving the strength-length contradiction.
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 method results in a mechanically robust protrusion with reduced vulnerability, suitable for applications like AFM probes, allowing for batch-wise production with oblique ends and minimal damage to cells during sample injection or manipulation.
Implementation Method 1
the opening is produced from the upper side by selective opening of the layer by means of an anisotropic plasma etching method which is matched to the material of the layer
Implementation Method 2
lining the surface of the mould by conformal thin film deposition
Implementation Method 3
a silicon oxide layer is grown on a silicon wafer by thermal oxidation
Implementation Method 4
a first recess is formed in said silicon oxide layer and in said silicon nitride layer by reactive ion etching
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A method of manufacturing a MEMS device comprising a main body and a protrusion. To provide a generic method of manufacturing a protrusion with reduced vulnerability, the method comprises - creating a recess in a wafer substrate, said recess comprising an upper recess section and a lower recess section. The upper recess section is created using anisotropic etching and the lower recess section is formed using corner lithography followed by directional etching. Finally, a filler material is introduced in the recess and at least part of the wafer substrate material is removed so as to expose the filler material introduced in the recess. Additionally, the claimed method allows for the batch-wise production of protrusions having oblique ends.