High Resistivity Substrate RF Module Noise Isolation
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Solution Overview
Problem
The high manufacturing cost of RF front-end modules (FEM) is limited by the expensive silicon on insulator (SOI) substrate and SIP/MCM process, which restricts the reduction of RF noise coupling and increases production costs.
Innovation Solution
A passive device and RF module are developed using a high resistivity substrate with shallow and deep trench device isolation regions, insulating layers, and passive components, along with noise blocking layers and guard rings to reduce RF noise coupling and improve electrical characteristics, while utilizing a high resistivity substrate that is less expensive than SOI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If SOI substrate is used, then RF noise coupling is reduced, but manufacturing cost increases
Solution Approach 1:
The patent replaces the expensive SOI substrate with a cheaper high resistivity silicon substrate. The shallow trench isolation and deep trench isolation structures are introduced to achieve the noise isolation function that would otherwise require the expensive SOI substrate, thereby reducing manufacturing cost while maintaining RF noise coupling reduction.
Solution Approach 2:
The patent employs a nested isolation structure where shallow trench isolation regions are combined with deep trench isolation regions. The deep trenches extend into the substrate beneath the shallow trenches, creating a multi-level isolation architecture that effectively blocks RF noise coupling paths without requiring the expensive SOI substrate structure.
2Adaptability or versatility
If SIP/MCM process is used, then RF module integration is achieved, but manufacturing cost increases
Solution Approach 1:
The patent combines multiple devices (passive devices, active devices, switching devices) onto a single high resistivity silicon substrate, integrating them into one unified structure. This monolithic integration approach eliminates the need for separate SIP/MCM packaging processes, reducing manufacturing complexity and cost while achieving the desired RF module integration.
Solution Approach 2:
The high resistivity silicon substrate serves multiple functions simultaneously: it provides the base for device fabrication, acts as a noise isolation medium through the trench structures, and enables integration of multiple device types. This multi-functionality reduces the need for additional specialized processes that would increase manufacturing cost.
3Object-affected harmful factors
If high resistivity substrate with deep trenches is used, then RF noise coupling is reduced, but device complexity increases
Solution Approach 1:
The isolation structure is segmented into two distinct components: shallow trench isolation regions near the surface and deep trench isolation regions extending deeper into the substrate. This segmentation allows each trench type to address specific noise coupling paths at different depths, achieving effective noise reduction through a systematic divided approach rather than a single complex structure.
Data Source
AI summary
In embodiments, a radio frequency (RF) module includes an RF switching device, an RF active device, a passive device and a control device formed on a high resistivity substrate. The passive device can include a shallow trench device isolation region having a plate shape and formed at a surface portion of the high resistivity substrate, deep trench device isolation regions extending downward from a lower surface of the shallow trench device isolation region so as to define at least one isolated region therebetween, at least one insulating layer formed on the high resistivity substrate, and at least one passive component formed on the insulating layer.