Tall Micro Structure Fabrication via Integrated Mask Electroplating
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Solution Overview
Problem
Conventional micro fabrication techniques face challenges in achieving high aspect ratios and maintaining precise lateral dimensions for micro structures, often resulting in variations and limitations in height and width ratios, particularly due to acidic electroplating baths that can erode photo resist and widen openings.
Innovation Solution
The method involves forming a seed electrode layer on a substrate with multiple conductive layers, using an opaque structure as a photo mask to define lateral dimensions, and iteratively adding layers through photo mask patterning and electroplating, allowing for precise control of lateral dimensions and increased height without the need for additional photo masks, suitable for both transparent and semi-transparent substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photo resist masking techniques are used to define lateral dimensions, then the fabrication process is simple, but the lateral dimensions vary significantly for structures taller than 100 microns
Solution Approach 1:
The patent transitions from defining lateral dimensions at the top surface (2D photo resist masking) to defining them at the base (3D structured substrate with integrated mask). The mask is formed as part of the substrate structure itself, extending vertically to support the microstructure, thereby maintaining lateral precision throughout the height of the structure.
Solution Approach 2:
The mask structure is prepared in advance as part of the substrate fabrication process, before the microstructure is grown. This preliminary formation of the mask with precise lateral dimensions ensures that subsequent electroplating or deposition processes maintain consistent lateral boundaries throughout the entire height of the microstructure.
2Manufacturing precision
If photo resist is used to define sidewalls, then the process is straightforward, but the sidewalls show variations and cannot maintain precise lateral dimensions for heights greater than 100 microns
Solution Approach 1:
The patent introduces a structured substrate with an integrated mask as an intermediary element that mediates between the growth process and the final lateral dimensions. This mask structure acts as a permanent template that guides material deposition, ensuring consistent lateral dimensions regardless of the structure's height.
Solution Approach 2:
The fabrication process is segmented into distinct stages: first forming the mask structure with precise lateral dimensions, then separately growing the microstructure through electroplating or deposition. This segmentation allows each process to be optimized independently, with the mask ensuring lateral precision and the growth process achieving the desired height.
3Manufacturing precision
If additional photo masks are applied at different heights to control lateral dimensions, then precision can be maintained, but the fabrication process becomes complex and time-consuming
Solution Approach 1:
The structured substrate with integrated mask serves multiple functions simultaneously: it provides mechanical support, defines lateral dimensions, and acts as a permanent mask throughout the entire height of the microstructure. This multi-functionality eliminates the need for multiple separate masking operations at different heights.
Solution Approach 2:
The mask function and substrate support function are merged into a single integrated structure. Rather than applying separate masks to the substrate surface, the mask is formed as an integral part of the substrate structure, combining multiple functions into one element and simplifying the overall fabrication process.
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 enables the creation of micro structures with well-defined lateral dimensions and high aspect ratios up to 1:100, overcoming conventional limitations by maintaining dimensional tolerance and avoiding variations in lateral dimensions, while allowing for easy height increase through repeated layer formation.
Implementation Method 1
irradiating the first layer of photo-patternable material with photons from the underside of the substrate. The substrate is at least partially transparent to photons and the first layer of conductive material is substantially opaque to the photons. A portion of the first layer of photo-patternable material is removed from on the first layer of conductive material
Data Source
AI summary
A micro structure includes a seed electrode layer on a substrate and a plurality of conductive layers on the seed electrode layer. The combined thickness of the seed electrode layer and the plurality of conductive layers can be more than 0.1 mm and the lateral dimensions of the seed electrode layer and the plurality of conductive layers vary less than 20% along the direction normal to a surface of the substrate and the micro structure has striations on an outer surface.