Ring Gate MOSFET Isolation Routing for High-Frequency Noise
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Solution Overview
Problem
Conventional high-frequency MOSFETs suffer from increased unnecessary gate capacities due to gate drawing wires crossing active regions, which hinder improvements in noise, maximum oscillation frequency, and characteristic stability.
Innovation Solution
The gate drawing wires are arranged outside the active region on an isolation region, and the bending portions of the ring-shaped gate electrode are formed on the isolation region, preventing unnecessary gate capacities and ensuring stable machining shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If gate drawing wires are arranged inside the active region to connect to the ring-shaped gate electrode, then the device complexity is reduced, but unnecessary gate capacities increase which deteriorates high-frequency characteristics
Solution Approach 1:
The gate drawing wires are routed in a different spatial dimension (outside the active region) rather than crossing through it. The wires extend laterally along the isolation region to connect to contact holes, eliminating vertical crossings through the active region and the associated parasitic gate capacities.
2Ease of manufacture
If gate drawing wires cross the active region, then the manufacturing process is simplified, but manufacturing precision deteriorates due to unstable machining shapes at crossing portions
Solution Approach 1:
The gate drawing wires are extracted from the active region and relocated to the isolation region. This separation removes the wires from areas where precise shape control is critical, eliminating the machining instability that occurs at wire crossing portions within the active region.
3Reliability
If gate drawing wires are arranged outside the active region on isolation region, then high-frequency characteristics are improved by eliminating unnecessary gate capacities, but device complexity increases
Solution Approach 1:
The gate electrode connection is segmented into distinct functional zones: the ring-shaped gate electrode in the active region for electrical function, and the gate drawing wires in the isolation region for interconnection. This segmentation allows each component to be optimized independently for its specific function.
4Area of stationary object
If gate drawing wires cross the active region, then the layout is more compact, but noise increases due to unnecessary gate capacities
Solution Approach 1:
The isolation region serves as an intermediary space that accommodates the gate drawing wires, separating them from the active region where noise-sensitive transistor operations occur. This intermediary zone prevents direct coupling between the wires and active devices, reducing noise interference.
Data Source
AI summary
In a semiconductor device, such as a MOSFET or the like, which is a high-frequency LSI achieving a low noise figure and a high maximum oscillation frequency and which has unit cells with a ring-shaped gate electrode arranged in an array, gate drawing wires connecting together the gate electrode and gate contact pad portions are arranged on a region excluding a drain region and a source region, that is, on an isolation region. Bending portions of the ring-shaped gate electrode are all formed on the isolation region. This therefore permits an improvement in high frequency characteristics such as noise, the maximum oscillation frequency, and the like while eliminating unnecessary gate capacity addition, and also permits small characteristic variation even if a machining shape of the bending portions of the gate electrode is unstable.