Hermetic Sealing via Segmented Silicon-Insulator Anodic Bonding
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Solution Overview
Problem
Existing methods for manufacturing hermetically sealed micro-electromechanical systems (MEMS) face challenges in achieving a reliable hermetic seal between silicon-insulator interfaces, often requiring specialized tooling to avoid short circuits and gas leaks, which complicates the anodic bonding process.
Innovation Solution
A method involving patterning silicon wafers to create recesses filled with insulator material, allowing for anodic bonding with silicon-only and insulator-only surfaces, enabling a hermetic seal using standard bonding tools and ensuring atomic-level sealing between silicon-insulator interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a composite wafer with both silicon and glass surfaces is used for anodic bonding, then electrical connections can be provided through the wafer, but specialized tooling is required to avoid short circuits
Solution Approach 1:
The wafer surface is segmented into distinct bonding regions: a first bonding surface consisting entirely of insulator material for electrical isolation during bonding, and a second bonding surface with silicon regions for electrical connections. This segmentation allows standard anodic bonding tooling to be used without risk of short circuits, while still providing through-wafer electrical connectivity through the silicon portions.
Solution Approach 2:
The insulator material is extracted to form a continuous first bonding surface that is removed or isolated during the anodic bonding process. This extraction creates a dedicated bonding interface that prevents electrical shorting between contacting electrodes, while the silicon regions remain available for electrical connections after bonding.
2Ease of manufacture
If standard anodic bonding equipment is used with a composite wafer, then the bonding process is simplified, but short circuits occur due to non-uniform wafer patterns
Solution Approach 1:
Different regions of the wafer surface are assigned different material compositions and functions: the first bonding surface is made entirely of insulator material to provide electrical isolation where electrodes contact, while the second bonding surface retains silicon regions for electrical connectivity. This local differentiation ensures both reliable electrical isolation during bonding and proper electrical connections afterward, using standard bonding equipment.
3Reliability
If the insulator-filled recesses do not extend completely through the composite wafer, then a hermetic seal is achieved at the silicon-insulator interfaces, but excess silicon remains on the bonding surface
Solution Approach 1:
The insulator material is filled into recesses that extend completely through the silicon wafer thickness before bonding. This preliminary action ensures that when the wafer is bonded, the insulator material is already in position to provide both hermetic sealing at the silicon-insulator interfaces and a uniform insulator-only first bonding surface for electrical isolation during anodic bonding.
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 ensures a reliable, hermetically sealed join between silicon-insulator interfaces during the manufacturing process, allowing for the creation of high-precision MEMS devices with improved accuracy and stability, such as gyroscopes and accelerometers, by applying an electrostatic field during anodic bonding.
Implementation Method 1
using an anodic bonding technique to bond the composite wafer and the second silicon wafer
Implementation Method 2
applying an electrostatic field during anodic bonding
Data Source
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AI summary
A method for providing hermetic sealing within a silicon-insulator composite wafer for manufacturing a hermetically sealed structure, comprising the steps of: patterning a first silicon wafer to have one or more recesses that extend at least partially through the first silicon wafer; filling said recesses with an insulator material able to be anodically bonded to silicon to form a first composite wafer having a plurality of silicon-insulator interfaces and a first contacting surface consisting of insulator material; and using an anodic bonding technique on the first contacting surface and an opposing second contacting surface to create hermetic sealing between the silicon-insulator interfaces, wherein the second contacting surface consists of silicon.