Polycrystalline Silicon Sensor Cavity Sealing for Low Damping
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Solution Overview
Problem
Existing semiconductor components face challenges in maintaining consistent low damping of the oscillating seismic mass over their lifetime, primarily due to outgassing from the cavity, which affects the quality of sensors like acceleration, pressure, and vibration sensors.
Innovation Solution
A method involving the deposition of a polycrystalline silicon layer on an oxide layer, followed by a crystalline silicon layer, and mounting a glass- or silicon-based lid on the crystalline layer to minimize outgassing and ensure optimal imperviousness, thereby reducing friction with gas molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cavity is provided for the seismic mass, then the sensor can detect acceleration, pressure, or vibration, but outgassing from the cavity causes damping to increase over time
Solution Approach 1:
The patent applies a lid made of glass or silicon that is bonded to the substrate, forming a sealed cavity. This thin film/shell structure prevents gas molecules from escaping the cavity while maintaining the necessary vacuum or controlled atmosphere for low damping, thus ensuring long-term reliability of the sensor
Solution Approach 2:
The patent introduces an oxide layer as an intermediary between the substrate and the lid. This oxide layer serves as a bonding interface that ensures hermetic sealing, preventing gas leakage while allowing the lid to be securely attached to the substrate, thereby maintaining cavity integrity over time
2Reliability
If a lid is mounted on the substrate to seal the cavity, then outgassing is prevented, but the bonding between lid and substrate must be perfectly impervious
Solution Approach 1:
The oxide layer acts as an intermediary bonding layer between the substrate and the lid. This intermediate layer compensates for surface irregularities and ensures uniform contact, achieving hermetic sealing without requiring extremely tight tolerances on the lid and substrate surfaces themselves
Solution Approach 2:
The sealing structure uses a composite approach combining the substrate, oxide layer, and lid materials. This multi-material construction leverages the complementary properties of each material to achieve reliable hermetic sealing that is more robust than what any single material could provide alone
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
The solution provides a semiconductor component with reduced damping variability over time, ensuring high-quality sensor performance by minimizing gas molecule interaction with the oscillating seismic mass.
Implementation Method 1
depositing an oxide layer on the substrate
Implementation Method 2
depositing a polycrystalline silicon layer on the oxide layer
Implementation Method 3
depositing a crystalline silicon layer on the substrate
Implementation Method 4
mounting a glass- or silicon-based lid on the crystalline silicon layer
Data Source
AI summary
A semiconductor component includes: a silicon-based substrate; an oxide layer atop the silicon-based substrate; an electronic component based on polycrystalline silicon; a crystalline silicon layer atop the silicon-based substrate and atop lateral faces of the oxide layer; and a lid connected to the crystalline silicon layer. The lid is a glass-based lid, a quartz-based lid or a silicon-based lid.