Stacked RF Switch Layout With Shared Capacitors for High Voltage
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Solution Overview
Problem
Conventional stacked RF switches face challenges in managing high voltages due to parasitic effects, leading to increased capacitor sizes that enlarge the tuner's overall footprint.
Innovation Solution
A stacked RF switch design with shared capacitors between top and bottom substrates, utilizing high-resistivity and low-resistivity substrates, metal vias for electrical connections, and metal-oxide-metal capacitors to compensate for parasitics, reducing the need for larger capacitors and minimizing the overall size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If larger capacitors are used at the front end of the transistor stack to compensate for parasitics and provide voltage swing, then voltage handling capability is improved, but the overall size of the tuner increases
Solution Approach 1:
The patent transitions from a planar capacitor layout to a three-dimensional stacked architecture where capacitors are distributed across multiple layers (top substrate, bottom substrate, and intermediate layers). This vertical stacking enables voltage handling improvement without proportional increase in footprint area, as the capacitive elements utilize the third dimension (height) rather than only horizontal space.
Solution Approach 2:
The capacitor system is segmented into multiple discrete capacitor elements distributed across different substrates and layers. Instead of using a single large capacitor, the total capacitance is achieved through series and parallel combinations of smaller capacitor units (e.g., first capacitor on top substrate, second capacitor on bottom substrate, third capacitor in intermediate layer), allowing optimized voltage distribution and reduced individual capacitor sizes.
2Reliability
If a stack of transistors in series is used to handle high voltage, then voltage handling capability is improved, but parasitic effects increase causing Pmax saturation
Solution Approach 1:
Capacitor elements are introduced as intermediary components between the series-connected transistors. These capacitors serve multiple functions: they provide voltage swing compensation for the transistor stack, isolate parasitic effects between adjacent transistors, and distribute voltage stress across multiple dielectric interfaces. The capacitive elements act as buffers that mitigate the harmful parasitic interactions inherent in high-voltage transistor stacks.
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to a stacked high-power radio frequency (RF) switch and methods of manufacture. The structure includes: a top substrate having at least one top transistor and metal wiring structures; and a bottom substrate having at least one bottom transistor and metal wiring structure. The bottom substrate is attached to the top substrate with the at least one top transistor being electrically connected to the at least one bottom transistor. A portion of the metal wiring structures of the top substrate and a portion of the metal wiring structures of the bottom substrate being at least one shared capacitor between the at least one top transistor and the at least one bottom transistor. Airgaps may be formed above the transistor.