Multilayer Fused Silica RF Circuits Without Wafer Fragility
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Solution Overview
Problem
Current methods for fabricating radio-frequency (RF) multi-layer circuits on fused silica are challenging due to the mechanical fragility of thin fused silica wafers, which can crack or break during layering, limiting the formation of multi-layer fused silica circuits with good RF properties.
Innovation Solution
A method involving deep silicon etching of a silicon wafer to create perforations and vias, followed by oxidation and conversion into fused silica, allows for the formation of robust multilayer RF circuits. This method includes filling the perforations with fused silica, metalizing the vias, and bonding multiple fused silica wafers to create interconnected RF circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thin fused silica wafers are used for RF circuits, then good RF properties are achieved, but mechanical strength deteriorates causing cracks or breaks during layering
Solution Approach 1:
The patent uses silicon oxide as a composite material that combines the superior RF properties of fused silica with the mechanical strength of silicon. The silicon oxide layer is formed through oxidation of silicon, creating a material that maintains structural integrity while providing excellent RF performance characteristics.
Solution Approach 2:
The patent changes the physical and chemical parameters of the substrate by oxidizing silicon to form silicon oxide. This transformation modifies the material properties to achieve both mechanical strength and RF performance, converting a mechanically strong but RF-suboptimal material (silicon) into a material with both desired properties (silicon oxide).
2Ease of manufacture
If conventional fabrication methods are used on fused silica, then manufacturing simplicity is maintained, but manufacturing precision deteriorates due to fragility limitations
Solution Approach 1:
The patent performs preliminary oxidation of the silicon substrate before proceeding with standard semiconductor fabrication processes. This preliminary action creates a mechanically robust silicon oxide layer that can withstand subsequent layering and processing steps, enabling precise manufacturing without the fragility issues of fused silica.
Solution Approach 2:
The silicon oxide layer acts as an intermediary material between the silicon substrate and the final RF circuit structure. It provides a stable, mechanically strong foundation that enables precise fabrication while maintaining the RF properties needed for the final device.
3Adaptability or versatility
If device range is extended to include more RF bands, then adaptability improves, but fabrication complexity increases due to material limitations
Solution Approach 1:
The silicon oxide material provides universal compatibility across multiple RF frequency bands (K, Ka, V, W, and G bands). By using this single material platform, the patent enables fabrication of diverse RF devices without requiring different material systems, thereby extending device range while maintaining relatively simple fabrication processes.
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 method enables the fabrication of RF circuits with improved mechanical strength and RF performance, extending the range of devices that can be fabricated, reducing costs, and enhancing yield by utilizing the superior RF properties of fused silica while overcoming its microfabrication limitations.
Implementation Method 1
oxidizing the silicon wafer to provide a fused silica wafer
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
A method of fabricating a radio-frequency multi-layer circuit includes perforating a silicon wafer to form a plurality of perforations, forming a plurality of vias spaced apart by the plurality of perforations, oxidizing the silicon wafer to provide a silicon oxide wafer, after forming the plurality of vias, filling the plurality of perforations with a fused silica layer to convert the silicon oxide wafer into a fused silica wafer, depositing within the plurality of vias and between the plurality of vias a metal layer connector to connect the plurality of vias, and bonding two or more fused silica wafers together such that the vias of the two or more fused silica wafers are connected to each other to form a radio-frequency circuit.