RF Switch Air-Gap Interconnect Layout for Lower Parasitic Capacitance
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Solution Overview
Problem
As semiconductor devices become more integrated, the proximity of metal interconnects leads to increased parasitic capacitance, which slows signal propagation and degrades device characteristics in RF switch devices, with existing solutions either increasing costs or reducing parasitic capacitance inefficaciously.
Innovation Solution
An RF switch device with an air gap over a gate electrode and metal interconnects positioned higher than the air gap, where the metal interconnects at least partially overlap the air gap vertically, preventing exposure and maintaining the air gap's width and height to reduce parasitic capacitance without the need for thick insulating layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the height of the air gap is increased to reduce parasitic capacitance, then parasitic capacitance decreases and device characteristics improve, but the upper end of the air gap may be exposed in subsequent processing
Solution Approach 1:
The patent introduces a floating metal layer at a higher elevation dimension to cover the air gap, transitioning from a two-dimensional planar structure to a three-dimensional stacked structure. This allows the air gap height to be increased for parasitic capacitance reduction while the floating metal layer prevents exposure during subsequent processing steps.
Solution Approach 2:
The floating metal layer acts as an intermediary element between the air gap and the subsequent processing steps. It mediates the conflict by providing physical coverage over the air gap to prevent exposure, while allowing the air gap to maintain its height for parasitic capacitance reduction.
2Reliability
If a thick insulating film is deposited to cover the air gap, then air gap exposure is prevented, but the via depth increases and manufacturing complexity increases
Solution Approach 1:
The patent uses a floating metal layer instead of a thick insulating film to cover the air gap. This alternative approach achieves air gap coverage without increasing via depth, as the floating metal layer is formed through standard deposition and patterning processes without requiring deep via formation.
3Reliability
If the air gap height is decreased to prevent exposure, then processing reliability improves, but parasitic capacitance reduction effectiveness decreases
Solution Approach 1:
The patent resolves this contradiction by adding a vertical dimension with the floating metal layer. This allows the air gap to maintain its full height for effective parasitic capacitance reduction, while the floating metal layer at a higher elevation prevents exposure during processing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration prevents air gap exposure, simplifies the via-forming process, reduces costs, and improves on-resistance by effectively covering adjacent air gaps with metal interconnects, thereby lowering parasitic capacitance and enhancing device performance.
Implementation Method 1
as the width W and the height H of the air gap 980 increase, the parasitic capacitance may decrease
Data Source
AI summary
Disclosed is an RF switch device and, more particularly, an RF switch device having an air gap over a gate electrode and a metal interconnect at a position higher than the air gap and that at least partially overlap the air gap in the vertical direction, thereby preventing exposure of an upper portion of the air gap in subsequent processing.