RF Switch Airgap Structures for Bulk Silicon Linearity
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Solution Overview
Problem
The high cost of manufacturing radio frequency (RF) switches is largely due to the use of trap-rich silicon on insulator (SOI) wafers, which are expensive and necessary for achieving high linearity, while devices on bulk Si substrates suffer from degraded performance due to noise, harmonics, and leakage currents.
Innovation Solution
The introduction of airgap structures formed in the substrate under the gate structures, extending to the source/drain regions, which improves RF parameters such as linearity and insertion loss, and can be implemented on bulk high resistivity silicon wafers using trench formation and insulator lining techniques, similar to integrated circuit technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SOI wafers are used to achieve high linearity and low harmonic distortion, then RF performance is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent applies local quality by creating airgap structures only in specific regions where needed for performance optimization. The airgaps are formed between the substrate and the device structure in localized areas, providing improved RF performance without requiring the entire wafer to be expensive SOI material. This selective application of airgaps allows bulk Si substrates to achieve performance comparable to SOI while reducing manufacturing costs.
2Ease of manufacture
If bulk Si substrates are used to reduce manufacturing cost, then manufacturing cost decreases, but RF performance degrades due to noise, harmonics, and leakage currents
Solution Approach 1:
The patent introduces airgap structures as intermediary elements between the bulk Si substrate and the RF device structure. These airgaps act as mediators that electrically isolate the device from the substrate, reducing leakage currents and noise while maintaining the cost advantage of bulk Si substrates. The airgaps serve as an intermediate layer that enables bulk Si to achieve RF performance comparable to expensive SOI wafers.
3Reliability
If airgap structures are formed in bulk Si substrates to improve linearity, then RF performance is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the substrate interaction into distinct regions: areas with airgap structures and areas without. The airgap structures themselves are segmented into multiple discrete elements that can be selectively positioned. This segmentation allows the complex function of improving linearity to be achieved through modular, localized structures rather than requiring complex modifications throughout the entire device.
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to radio frequency (RF) switches with airgap structures and methods of manufacture. The structure includes a substrate with at least one airgap structure formed in a well region under at least one gate structure, and which extends to a junction formed by a source/drain region of the at least one gate structure.