Semiconductor Device Segmented Finger Electrodes Reduce Drain-to-Source Capacitance
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Solution Overview
Problem
Semiconductor RF switches face a trade-off between low on-state resistance for reduced power loss and low off-state capacitance for improved switching speed, where increasing metal width to reduce resistance also increases capacitance, compromising device performance.
Innovation Solution
The semiconductor device employs a metalization structure with source and drain finger electrodes segmented into main and isolated segments, where the main segments have a normal width and reduced width portions, reducing capacitive coupling without significantly increasing on-state resistance, thereby minimizing off-state capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the width of source and drain metals is increased to reduce on-state resistance, then power loss is reduced, but off-state capacitance is adversely increased
Solution Approach 1:
The source and drain metals are segmented into multiple fingers rather than using a single wide metal structure. This segmentation allows the device to achieve low on-state resistance through multiple parallel conduction paths while reducing off-state capacitance by decreasing the continuous metal area that creates parasitic coupling.
Solution Approach 2:
Different regions of the metal structure have different widths - the metals are wider at the contact regions to reduce resistance but narrower in the finger regions to reduce capacitance. This local variation in metal width optimizes both parameters simultaneously.
2Loss of energy
If the device layout area is increased to reduce on-state resistance, then power loss is reduced, but off-state capacitance is adversely increased
Solution Approach 1:
The device layout is segmented into multiple interdigitated source and drain fingers that are closely spaced. This configuration achieves low on-state resistance through multiple parallel conduction paths within a compact area, avoiding the need for large layout area while preventing excessive capacitance.
Solution Approach 2:
The metal structures extend in multiple dimensions with interdigitated fingers arranged in a planar pattern. This multi-dimensional arrangement maximizes the conduction area for low resistance while minimizing the overlapping area that contributes to parasitic capacitance.
Data Source
AI summary
A semiconductor device includes a source finger electrode coupled to a source region in a semiconductor die, a drain finger electrode coupled to a drain region in the semiconductor die, where the source finger electrode includes at least one isolated segment and a main segment having a first portion and a second portion narrower than the first portion, whereby the source finger electrode reduces a drain-to-source capacitance of the semiconductor device. A common source rail is electrically coupled to the at least one isolated segment and the main segment of the source finger electrode. The drain finger electrode includes at least one isolated segment and a main segment having a first portion and a second portion narrower than the first portion. A common drain rail is electrically coupled to the at least one isolated segment and the main segment of the drain finger electrode.