SOI Substrate Layer Stack for RF Loss and Dislocation Control
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Solution Overview
Problem
Existing semiconductor-on-insulator substrates for RF applications face issues with increased dislocation migration due to low interstitial oxygen content, leading to substrate losses and overlay problems during lithography, which affect the production yield and signal integrity.
Innovation Solution
Introducing a penetration layer with low interstitial oxygen content and higher resistivity between the passivation layer and the silicon support substrate, combined with a passivation layer that reduces parasitic losses and dislocation migration, using materials like monocrystalline or polycrystalline silicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a low interstitial oxygen content silicon support substrate is used to reduce substrate losses, then parasitic signal losses are reduced, but dislocation migration increases leading to slip lines and overlay problems
Solution Approach 1:
The substrate structure is segmented into multiple functional layers: a standard oxygen-content support substrate provides mechanical stability, while separate low-oxygen penetration and passivation layers handle electrical isolation. This segmentation allows each layer to optimize for its specific function without compromising the other.
Solution Approach 2:
Different regions of the substrate structure have different oxygen contents tailored to their specific functions. The support substrate has standard oxygen content for mechanical strength, the penetration layer has low oxygen content for electrical isolation, and the passivation layer has low oxygen content to prevent dislocation migration at critical interfaces.
2Object-generated harmful factors
If the penetration layer thickness is increased to reduce RF signal penetration into the substrate, then substrate losses are reduced, but device complexity increases
Solution Approach 1:
The oxygen content parameter is changed in specific layers (penetration and passivation layers have low oxygen content compared to the support substrate) to achieve electrical isolation and dislocation prevention without requiring excessive layer thickness, thus controlling device complexity.
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
Reduces substrate losses and dislocation migration, maintaining signal integrity while allowing standard CMOS fabrication methods, thereby improving production yield and reducing unwanted slip lines.
Implementation Method 1
A low Oi content makes silicon more sensitive to dislocation migration. Oxygen interstitial atoms tend to attach to silicon atoms and aggregate into small precipitates of SiO2 that prevent migration of dislocations into the crystal lattices.
Implementation Method 2
the penetration layer is a higher resistive silicon layer with lower interstitial oxygen content than the silicon support substrate
Data Source
AI summary
A semiconductor-on-insulator substrate for use in RF applications, such as a silicon-on-insulator substrate, comprises a semiconductor top layer, a buried oxide layer and a passivation layer over a support substrate. In addition, a penetration layer is provided between the passivation layer and the silicon support substrate to ensure sufficient high resistivity below RF features and avoid increased migration of dislocations in the support substrate. RF devices may be fabricated on and/or in such a semiconductor-on-insulator substrate.