Three-Sided Pyramidal MEMS Protrusion Mold
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Solution Overview
Problem
Existing methods for manufacturing pyramidal tips for MEMS devices result in protrusions with a four-sided shape, which are less sharp due to multiple apices and larger cone angles, making them less suitable for scanning applications like AFM probes, and are costly and time-consuming to produce.
Innovation Solution
A method using a mold with a sacrificial layer and isotropic etching to create a three-sided pyramidal protrusion with a single apex, allowing for the mass production of MEMS devices with a small half-cone angle and sharp apex, using polycrystalline silicon and silicon oxide layers, and anisotropic etching to separate the device from the base substrate without fully dissolving the silicon base material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a four-sided pyramidal mold is used, then the manufacturing process is simple and well-established, but the resulting protrusion has multiple apices and larger cone angle making it less sharp
Solution Approach 1:
The patent transitions from a symmetric four-sided pyramidal mold to an asymmetric three-sided pyramidal mold. The mold is defined by three plane sections that are not equivalent, with specific orientations relative to the substrate surface. This asymmetric geometry enables the formation of a protrusion with a single sharp apex and smaller half-cone angle, directly addressing the sharpness requirement while maintaining manufacturability through a systematic mold design approach.
Solution Approach 2:
The patent applies different geometric characteristics to different parts of the mold structure. The three plane sections of the mold have specific orientations and slopes that are optimized for creating a sharp apex, while the base of the mold maintains a configuration suitable for mass production. This local optimization of geometric properties allows the mold to produce protrusions with superior sharpness while remaining compatible with existing manufacturing processes.
2Manufacturing precision
If dry etching is used to remove base material, then a three-sided pyramidal tip can be formed, but manufacturing cost and time increase
Solution Approach 1:
The patent introduces a sacrificial layer as an intermediary material between the base substrate and the protrusion structure. This sacrificial layer is deposited over the base substrate and patterned to define the three-sided pyramidal geometry. By using this intermediary layer, the patent avoids the need for time-consuming dry etching of the base material while still achieving the desired precise geometry. The sacrificial layer can be removed through simpler, faster processes, thereby increasing manufacturing productivity.
Solution Approach 2:
The patent performs preliminary actions by depositing and patterning the sacrificial layer before forming the final protrusion structure. The three-sided pyramidal shape is pre-defined in the sacrificial layer, which then serves as a template for subsequent material deposition and processing. This preliminary geometry definition eliminates the need for complex and time-consuming dry etching steps, allowing for faster mass production while maintaining precise geometric control.
3Adaptability or versatility
If silicon etching is used, then a pyramidal tip can be manufactured, but the tip material is limited to silicon
Solution Approach 1:
The patent uses a sacrificial layer as an intermediary that can be removed after transferring the geometry to the desired tip material. This intermediary approach allows the use of various materials (silicon nitride, diamond, metal, polymer) for the final protrusion while maintaining precise geometric control. The sacrificial layer serves as a temporary structure that defines the shape, allowing subsequent material deposition and processing to create the final tip in the desired material without compromising geometric precision.
Solution Approach 2:
The patent changes the material parameter from silicon-specific etching to a more general geometric definition approach. By using a sacrificial layer with specific geometric properties and removing it through controlled processes, the patent enables the formation of pyramidal tips in various materials. This parameter change from material-specific processing to geometry-focused processing provides versatility in tip material selection while maintaining manufacturing precision through controlled geometric parameters.
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
Enables the reliable and speedy manufacturing of sharp, three-sided MEMS devices with a single apex, improving their scanning capabilities and reducing production time and cost compared to existing methods.
Implementation Method 1
isotropically etching the sacrificial layer of the mold with an isotropic etchant capable of etching the sacrificial layer so as to separate the MEMS device from at least the base substrate of the mold
Implementation Method 2
The most common mold geometry is a square (four-sided) pyramid etched into a Si wafer via anisotropic etching
Data Source
AI summary
A method of providing a MEMS device, such as an AFM probe, having a three-sided pyramidal protrusion is made using a multitude of MEMS method steps. To allow the reliable and speedy manufacture of such a MEMS device having a three-sided protrusion on a massive scale, wherein the protrusion has a relatively small half-cone angle and a single apex, a mold is used. The mold includes a sacrificial layer on top of a base substrate. The method of providing the MEMS device includes:providing an area at the first side of the mold which area comprises a pit with a layer of protrusion material,patterning the layer of protrusion material to the desired shape, andisotropically etching the sacrificial layer of the mold with an isotropic etchant capable of etching the sacrificial layer so as to separate the MEMS device from at least the base substrate of the mold.