Differential Microstructure Wet Etching via Mask Cooling
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Solution Overview
Problem
Conventional wet etching methods face challenges in achieving smooth vertical vias or grooves and processing microstructures of different sizes on the same workpiece, particularly with single crystal silicon, due to anisotropic etching directions and limited size versatility.
Innovation Solution
A method involving selective temperature control during wet etching by using a mask with a light shielding and base layer, cooled by liquid nitrogen, to create a temperature difference on the workpiece, allowing for differential etching rates across the surface and enabling the processing of micro vias and grooves with higher depth-to-width ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional wet etching is performed on single crystal silicon, then etching can be achieved, but the etching direction is fixed at 54.7° making it difficult to obtain smooth vertical vias or grooves
Solution Approach 1:
The patent applies local quality by cooling specific regions of the mask with liquid nitrogen to create localized temperature differences. This causes different etching rates in different areas, enabling vertical etching in cooled regions while maintaining the ability to control etching direction locally rather than being constrained by the global 54.7° crystallographic direction.
Solution Approach 2:
The patent changes the temperature parameter of the etching process by introducing liquid nitrogen cooling to the mask. This temperature change modifies the etching rate and etching direction, allowing deviation from the standard 54.7° angle to achieve vertical vias and grooves with improved manufacturing precision.
2Adaptability or versatility
If conventional wet etching is performed on a workpiece, then etching can be achieved, but micro vias and grooves with different sizes cannot be processed on the same workpiece
Solution Approach 1:
The patent uses selective cooling of different regions of the mask to create spatially varying temperature distributions. This enables different etching rates across the workpiece surface, allowing micro structures of different sizes to be processed simultaneously on the same workpiece while maintaining appropriate etching uniformity for each region.
Solution Approach 2:
The patent introduces dynamic temperature control by continuously cooling the mask with liquid nitrogen during the etching process. This dynamic cooling system allows real-time adjustment of etching conditions across different areas, enabling versatile processing of various microstructure sizes while maintaining manufacturing precision through active thermal management.
3Manufacturing precision
If a mask is cooled with liquid nitrogen to create temperature differences, then differential etching rates can be achieved, but the mask must have good thermal conductivity and structural stability
Solution Approach 1:
The patent employs a composite mask structure combining a metal substrate (providing thermal conductivity and structural stability) with a photoresist pattern layer (providing etching selectivity). This composite construction satisfies the demanding requirements for thermal conductivity, structural stability, and differential etching control without excessive device complexity.
Solution Approach 2:
The mask serves as an intermediary element that transfers the cooling effect from liquid nitrogen to the workpiece while maintaining structural integrity. The mask's composite structure mediates between the thermal management requirements and the etching precision requirements, enabling differential etching control without overly complicating the overall device structure.
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 precise and efficient processing of micro vias and grooves with depth-to-width ratios greater than 5, surpassing the limitations of conventional wet etching by controlling etching rates through temperature differences, resulting in higher processing accuracy and versatility.
Implementation Method 1
a base layer, made of stainless steel or copper which are not easily etched and have good thermal conductivity
Implementation Method 2
continuously cooling the mask affixed to the surface of the workpiece to be processed
Implementation Method 3
Chemical reagents are adopted in the wet etching to etch or dissolve the material to be processed so as to remove the materials
Implementation Method 4
performing photoetching on a processing surface of a workpiece to be processed to develop the workpiece; wherein a pattern area to be processed on the processing surface of the workpiece is exposed
Data Source
AI summary
A method for synchronous wet etching processing of differential microstructures, including the following steps: step a: performing photoetching on a processing surface of a workpiece to be processed to develop the workpiece; step b: affixing a mask to a surface opposite to the processing surface of the workpiece; step c: continuously cooling the mask; step d: placing the cooled mask and the workpiece in a wet etching device; and adding an etchant to the processing surface of the workpiece to start etching; step e: removing the mask and the workpiece from the wet etching device after the set etching time; separating the mask and the workpiece to obtain a workpiece with a etching structure. A temperature difference is formed between the pattern area to be processed and the retaining area.