Resonator Recess Fabrication With Laser-Selective Vertical Etching
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Solution Overview
Problem
Chemical etching techniques for producing microtechnical parts, such as resonators, fail to create recesses with straight flanks, resulting in inclined sides and variations in surface area with depth, leading to inaccuracies in theoretical calculations and characteristics.
Innovation Solution
A manufacturing method using a femtosecond laser to modify the substrate, making it transparent to chemical etching, allowing for the creation of complex internal recesses with straight and vertical sides by selectively targeting areas for chemical attack, preserving the original shape and improving piezoelectric coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If chemical etching is used to produce recesses, then the manufacturing process is simple, but the recesses cannot have straight flanks and the surface area varies with depth
Solution Approach 1:
The patent applies preliminary action by first depositing a sacrificial layer (such as silicon dioxide) over the recess area before chemical etching. This sacrificial layer is then selectively removed through the mask openings, allowing the chemical etchant to access and etch the substrate vertically downward. This preliminary preparation enables straight-flanked recesses that cannot be achieved by chemical etching alone.
Solution Approach 2:
The patent introduces an intermediary sacrificial layer (silicon dioxide or other materials) between the mask and the substrate. This intermediary layer acts as a mediator that controls the etching process: it is deposited conformally, patterned through the mask, and then selectively removed to create vertical sidewalls. The intermediary enables the chemical etchant to proceed vertically without the inclined sidewalls that would result from direct etching.
2Device complexity
If direct chemical etching is used, then the process is straightforward, but theoretical calculations do not match practical results due to profile variations
Solution Approach 1:
The patent changes the physical and chemical parameters of the etching process by introducing controlled intermediate steps. The sacrificial layer deposition, patterning, and selective removal transform the etching from a direct single-step process into a multi-step process with controlled parameters. This allows precise control over recess depth, width, and sidewall angle, making the actual etched profile match theoretical calculations.
3Reliability
If complex internal recesses are required, then functional performance improves, but traditional manufacturing methods cannot achieve the required precision
Solution Approach 1:
The patent segments the recess formation process into distinct stages: sacrificial layer deposition, mask patterning, selective removal, and controlled etching. This segmentation allows each step to be optimized independently for precision. The sacrificial layer is deposited conformally to ensure uniform thickness, the mask is patterned with precise dimensions, and the selective removal creates well-defined etching paths, all contributing to high geometric precision for complex internal recesses.
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 production of resonators with increased piezoelectric coupling and reduced power consumption, achieving a 30% gain in motional capacitance and precise structural modifications, while maintaining the integrity of the original shapes and reducing material loss.
Implementation Method 1
modifying the structure of the component by the action of a laser whose pulse duration is of the order of a femtosecond
Implementation Method 2
locally causing a modification of the structure by absorption of several photons
Implementation Method 3
bringing a chemical agent which makes it possible to dissolve the zones whose structure has been modified
Data Source
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Figure 3a~3e
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AI summary
The present invention relates to a method for manufacturing a resonator in a substrate, characterized in that it comprises the following steps: a) modifying the structure of at least one zone of the substrate in order to make said at least one zone more selective; b) etching said at least one zone in order to selectively manufacture said resonator.