MEMS Cavity Height Control via Partially Buried Insulating Pads
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Solution Overview
Problem
Existing methods for producing MEMS and NEMS devices struggle to independently adjust the height of cavities between suspended elements and substrates while maintaining significant insulating pad height, and cannot produce cavities of varying heights efficiently.
Innovation Solution
A method involving the production of insulating pads on a semiconductor substrate, where the height of these pads is fixed by burying them partially in the substrate, and then adjusting the cavity height by etching or adding semiconductor material, allowing for the formation of cavities with low heights and varying heights between 10 nm and 5 μm, while maintaining insulating pad thickness between 0.1 μm and 10 μm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulating pads of significant height are produced to ensure good insulation and reduce parasitic capacitance, then insulation performance is improved, but cavity height becomes dependent on pad height and cannot be independently adjusted
Solution Approach 1:
The invention divides the height determination into two independent segments: insulating pad height is determined by oxidation depth, while cavity height is independently determined by subsequent etching depth. This segmentation allows each parameter to be controlled separately without mutual dependency.
Solution Approach 2:
The insulating pads are formed in advance through oxidation before the cavity formation step. This preliminary action establishes the pad height first, then allows independent adjustment of cavity height through controlled etching, enabling flexible parameter optimization.
2Productivity
If low cavity height is produced to enable efficient actuation with low control voltages and improve signal detection, then operational efficiency is improved, but insulating pad height must be reduced compromising insulation
Solution Approach 1:
The process separates pad height control (via oxidation) from cavity height control (via etching), allowing the cavity to be made very thin for efficient actuation while the insulating pads maintain sufficient height for proper electrical insulation and reduced parasitic capacitance.
Solution Approach 2:
The invention changes the control parameter for cavity height from pad height to etching depth, enabling independent optimization of cavity dimensions for operational efficiency while maintaining pad dimensions for insulation reliability.
3Ease of manufacture
If uniform insulating pads are produced across the substrate, then manufacturing simplicity is maintained, but cavities of different heights cannot be produced
Solution Approach 1:
The etching step applies local quality by allowing different etching depths in different regions of the substrate. Masking patterns enable selective etching, creating cavities of varying heights in different areas while maintaining uniform insulating pad formation across the entire substrate.
Solution Approach 2:
Insulating pads are formed uniformly across the substrate in advance through oxidation before any selective etching occurs. This preliminary uniform formation maintains manufacturing simplicity, while subsequent selective etching introduces local variations for different cavity heights.
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 MEMS and NEMS devices with low cavity heights and significant insulating pad thickness, facilitating efficient actuation and signal detection, and allowing for the creation of cavities of different heights, enhancing operational efficiency and signal quality.
Implementation Method 1
Document US 2009/0142872 presents a method of manufacturing a cMUT transducer in which the insulating pads intended to hold the membrane are formed by oxidation of the semiconductor substrate.
Implementation Method 2
b) modification, by at least one etching and /or at least one addition of material, of the distance between at least one given zone among said zones of said upper face and the top of insulating pads
Implementation Method 3
b) modification, by at least one etching and /or at least one addition of material, of the distance between at least one given zone among said zones of said upper face and the top of insulating pads
Data Source
Figure 1~2D
Figure 2E~3D
Figure 4A~4E
AI summary
The invention relates to an improved process for producing a device comprising a plurality of cavities (150a, 150b) defined between a substrate (100) based on at least one given semiconductor material and a membrane (140) resting on the tops of insulating pads (104a, 104b, 104c) that protrude from the substrate, the process allowing the height of the one or more cavities to be adjusted independently of that of the insulating pads and cavities of different heights to be produced.