Laterally Doped MEMS Resonator With Low-Temperature Vent Sealing
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Solution Overview
Problem
Conventional MEMS fabrication methods using epitaxial silicon lids degrade temperature-sensitive materials and result in undesired deposition, particularly in MEMS structures with piezoelectric layers.
Innovation Solution
The use of metal-sealed oxide-release vents at lower temperatures and narrow passageways to plug vents without degrading piezoelectric layers, combined with lateral doping techniques to enhance doping depth and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If epitaxial silicon lid growth is used to seal MEMS chambers, then hermetic sealing is achieved, but temperature-sensitive materials are degraded and undesired deposition occurs
Solution Approach 1:
The patent changes the temperature parameter from high-temperature epitaxial growth (>1000°C) to low-temperature metal deposition (<400°C), thereby achieving hermetic sealing without degrading temperature-sensitive materials like piezoelectric layers
Solution Approach 2:
The patent introduces metal seals as an intermediary substance to achieve hermetic sealing, replacing the direct epitaxial growth process. The metal seals are deposited through oxide-release vents to plug them and provide hermetic sealing without requiring high temperatures
2Reliability
If epitaxial silicon lid growth is used to seal MEMS chambers, then hermetic sealing is achieved, but undesired deposition occurs in the chamber
Solution Approach 1:
The patent uses metal seals deposited through oxide-release vents as an intermediary to achieve sealing without requiring line-of-sight deposition into the chamber. The metal is deposited at the vent openings rather than inside the chamber, eliminating undesired deposition
Solution Approach 2:
The patent segments the sealing process by using narrow lateral passageways that are plugged with metal seal, separating the sealing function from the chamber interior. This prevents deposition material from entering the chamber while still achieving hermetic sealing
3Manufacturing precision
If lateral doping is used to enhance doping depth, then doping efficiency is improved, but process complexity increases
Solution Approach 1:
The patent transitions from vertical doping (through-thickness) to lateral doping (through sidewalls of trenches), changing the dimension of dopant delivery. This enables deeper doping without proportionally increasing process complexity by using the sidewall surface area for dopant delivery
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 prevents material degradation and mechanical/electrical disruption while enabling efficient MEMS fabrication with temperature-sensitive materials, reducing process temperatures and improving structural integrity.
Implementation Method 1
a laterally-doped, piezoelectrically-actuated MEMS resonator
Implementation Method 2
metal-sealed oxide-release vents
Data Source
AI summary
A semiconductor device includes a first silicon layer with first and second regions of substantially different dopant concentration and a resonant MEMS member formed in the first region. A piezoelectric layer is disposed over the resonant MEMS member and conductive material is disposed over the piezoelectric layer and patterned to form first and second electrodes.