Segmented RF Switch Channel Regions for Linearity
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Solution Overview
Problem
Radio frequency (RF) switches face a trade-off between insertion loss and isolation, with high power handling requiring large circuit elements that increase capacitance, leading to non-linearities and reduced linearity performance, necessitating an improvement in the figure of merit and trade-off between these parameters.
Innovation Solution
The RF switch design features a substrate with a body layer having multiple diffusion areas and channel regions, with a first current collection diffusion integral to both, and a buried oxide layer, dividing the distance between drain/source diffusions and channel regions to reduce total resistance and enhance power handling while maintaining linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If large circuit elements are used to achieve low insertion loss and high power handling capability, then power handling capability is improved, but isolation deteriorates due to increased capacitance
Solution Approach 1:
The patent divides the channel region into multiple parallel channel regions separated by current collection diffusions. This segmentation reduces the capacitance of individual channel regions while maintaining the overall current handling capability, thereby improving isolation without sacrificing power handling capability
Solution Approach 2:
The patent introduces current collection diffusions that extend in the Y-direction (orthogonal to the X-direction where channel regions are arranged). This dimensional change creates additional current collection paths and reduces the effective capacitance between channel regions, improving isolation while maintaining power handling
2Loss of energy
If large circuit elements are used to achieve low insertion loss, then insertion loss is improved, but linearity deteriorates due to non-linearities in large capacitances
Solution Approach 1:
The patent segments the channel into multiple smaller parallel channel regions. This reduces the capacitance size of each region, thereby reducing non-linearities and improving linearity performance while maintaining low insertion loss through the parallel configuration
Solution Approach 2:
The patent introduces current collection diffusions at specific locations between channel regions to locally collect and redistribute current. This creates more uniform current distribution across the channel, reducing local non-linearities and improving overall linearity
3Power
If the size of circuit elements is increased to reduce ON state resistance, then power handling is improved, but OFF state capacitance increases, worsening the figure of merit
Solution Approach 1:
The patent divides the channel region into multiple smaller channel regions with current collection diffusions between them. This segmentation reduces the OFF state capacitance of each region while the parallel configuration maintains low ON state resistance, thereby improving the figure of merit (RON×COFF)
Solution Approach 2:
The current collection diffusions act as intermediary structures between the channel regions and the source/drain regions. These intermediaries provide additional current collection paths that reduce the effective resistance while the segmented structure reduces capacitance, improving the figure of merit
Data Source
AI summary
An apparatus with a body layer disposed over a substrate is disclosed. The body layer has first and second diffusion areas with a first current collection area between the two. A plurality of first drain/source (D/S) diffusions spaced parallel with one another resides within the first diffusion area. A plurality of first channel regions resides within the first diffusion area such that each of the plurality of first channel regions resides between an adjacent pair of the plurality of the first D/S diffusions. A plurality of second D/S diffusions resides within the second diffusion area and are spaced parallel with one another. A plurality of second channel regions reside within the second diffusion area such that each of the plurality of second channel regions resides between an adjacent pair of the plurality of the second D/S diffusions. A first current collection diffusion resides within the first current collection area.