SOI Switch with Deep Trench Isolation for RF Linearity
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Solution Overview
Problem
High resistivity silicon substrates used in RF devices suffer from leakage and harmonic distortion due to extended depletion regions, which affect the linearity and performance of wireless communication components in cellular telephones.
Innovation Solution
The introduction of an air gap under the device region bounded by an etch stop layer and deep trench isolation structures, which improves isolation and reduces harmonic distortion by embedding a SiGe etch stop layer and forming cavities and deep trench isolation structures surrounding the device region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high resistivity silicon substrates are used to achieve vertical isolation and linearity, then substrate carrier induced harmonics are reduced, but depletion regions extend deep into the substrate causing leakage between neighboring devices
Solution Approach 1:
The substrate is segmented into isolated regions using deep trench isolation structures that physically divide the continuous substrate into separate zones. These trenches extend through the depleted region and fill the space between device depletion regions, preventing lateral leakage currents while maintaining the high resistivity substrate's vertical isolation and linearity benefits
Solution Approach 2:
An intermediary material (such as conductive fill or insulating material) is introduced into the deep trench isolation structures to actively manage depletion region interactions. This intermediary blocks leakage paths between neighboring devices while allowing the high resistivity substrate to maintain its linearity performance
2Reliability
If triple wells are used to block depletion regions from merging, then DC substrate current interaction is prevented, but merged triple well depletion regions result in harmonic distortion due to coupling between n-type triple well regions
Solution Approach 1:
The isolation approach transitions from two-dimensional planar triple well structures to three-dimensional deep trench isolation that extends vertically through the substrate. This additional vertical dimension allows the trenches to intersect and block depletion region merging more effectively, preventing both DC substrate current interaction and the coupling that causes harmonic distortion between n-type regions
3Reliability
If triple well depletion regions are used to isolate devices, then DC substrate current is blocked, but non-linear capacitance is added with respect to varying voltage resulting in additional harmonic distortion
Solution Approach 1:
The deep trench isolation structures serve as intermediary elements that replace the triple well depletion regions for isolation purposes. By using physically separated trenches filled with appropriate materials, the need for extensive triple well depletion regions is reduced, thereby minimizing the non-linear capacitance effects while maintaining DC substrate current blocking capability
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to a switch with local silicon on insulator (SOI) and deep trench isolation structures and methods of manufacture. The structure a structure comprises an air gap located under a device region and bounded by an upper etch stop layer and deep trench isolation structures.