Micromechanical Valve Stack Etching for Stable Valve Flaps
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Solution Overview
Problem
Current methods for manufacturing micromechanical devices, such as micropumps and micromembrane pumps, face challenges including unstable valve flaps during handling and processing, high waste rates due to underetching, and limitations in size reduction due to anisotropic etching processes like KOH etching.
Innovation Solution
A method involving the bonding of two substrates with patterned trench structures to form a stable substrate stack, followed by the exposure of cavities within the stack using a CMOS-compatible dry etching process, which allows for the formation of micromechanical structures like valve flaps and ridges without the need for initial processing of individual substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If KOH wet chemical etching is used to pattern microvalves, then the etching process is well-controllable and achieves appropriate etching results, but the anisotropic etching causes underetching leading to higher waste rate and prevents further size reduction
Solution Approach 1:
The patent changes the etching parameter from wet chemical KOH etching to dry plasma etching. This parameter change eliminates the underetching problem inherent in wet etching, achieving precise vertical sidewalls without lateral etching, thereby reducing waste material while maintaining manufacturing precision.
Solution Approach 2:
The patent replaces the chemical wet etching process with a physical plasma-based dry etching process. This substitution eliminates the capillary action and surface tension effects that cause underetching in wet processes, enabling precise pattern transfer without material waste.
2Ease of manufacture
If substrates are processed independently before bonding, then valve flaps and ridges can be patterned, but the valve flaps are unstable and prone to breakage during handling and processing
Solution Approach 1:
The patent inverts the conventional processing sequence by bonding the substrates first and then patterning the valve structures. This inversion provides mechanical support during processing, preventing valve flap breakage while maintaining ease of manufacture through standard bonding procedures.
Solution Approach 2:
The patent provides beforehand cushioning by bonding the substrates together before processing the delicate valve structures. This creates a mechanically robust assembly that protects the valve flaps from breakage during subsequent handling and processing steps.
3Manufacturing precision
If KOH etching process is used, then appropriate etching results are achieved, but particles are generated through sharp edges causing cross contamination
Solution Approach 1:
The patent replaces wet chemical etching with dry plasma etching, which eliminates the generation of particulate contamination. The plasma process provides clean etching without the sharp edge formation and particle generation characteristic of wet chemical processes, thereby preventing cross contamination.
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 enhances the stability of the valve flaps, reduces the risk of breakage during processing, and enables the manufacture of smaller, more efficient micromechanical devices with reduced dead volume and material usage.
Implementation Method 1
exposing the at least one cavity by patterning a recess into the upper and/or lower surface of the substrate stack, wherein, in the method, the step of exposing the at least one cavity is performed after arranging the two substrates into the substrate stack
Data Source
AI summary
A method for manufacturing at least one micromechanical device includes:providing a first and a separate second substrate, each having two surfaces spaced parallel to each other with a predetermined thickness;patterning a first trench structure into one of the two surfaces of the first substrate, and a second trench structure into one of the two surfaces of the second substrate;arranging the patterned surfaces of the two substrates with respect to each other such that a substrate stack with an upper and a lower surface is defined and the first and/or second trench structure forms at least one cavity therein;thinning the substrate stack from its upper and/or lower surface;exposing the at least one cavity by patterning a recess into the upper and/or lower surface of the substrate stack,wherein exposing the at least one cavity is performed after arranging the two substrates into the substrate stack.Further embodiments relate to a valve manufactured by means of the method and to a micromechanical pump.