HEMT Drain Contact Segmentation for Lower Output Capacitance
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Solution Overview
Problem
High-electron-mobility transistors (HEMTs) face performance degradation and reliability issues due to heat generated under the gate, which increases output capacitance when gate-to-gate pitch is increased for improved heat dissipation, degrading the Ft/Fmax figure of merit.
Innovation Solution
A semiconductor structure with a partially blocked drain ohmic contact, featuring a gap or open space in the ohmic contact, which reduces drain capacitance by using smaller, spaced terminal connections and a dielectric material to lower capacitance, and an isolation structure under the ohmic contact to further reduce capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the gate-to-gate pitch is increased to improve heat dissipation, then heat dissipation is improved, but the output capacitance increases which degrades the Ft/Fmax figure of merit
Solution Approach 1:
The drain ohmic contact is segmented into multiple separated contact regions rather than a continuous contact. This segmentation reduces the total capacitance between the drain contact and gate while still providing adequate heat dissipation pathways, thus improving the Ft/Fmax figure of merit without sacrificing thermal performance
Solution Approach 2:
The patent applies different contact configurations to different regions: the ohmic contact is positioned closer to the gate in some areas and farther in others, creating a non-uniform distribution that optimizes both capacitance reduction and heat dissipation locally across the device structure
2Reliability
If the gate-to-gate pitch is decreased to reduce output capacitance, then the Ft/Fmax figure of merit is improved, but heat dissipation deteriorates
Solution Approach 1:
By dividing the drain ohmic contact into separated segments, the patent reduces capacitance effects that would otherwise require larger pitch spacing, allowing tighter gate spacing for improved Ft/Fmax while maintaining adequate thermal pathways through the segmented contact structure
3Reliability
If the ohmic contact is positioned closer to the gate to reduce capacitance, then output capacitance is reduced, but heat accumulation increases
Solution Approach 1:
The segmented ohmic contact configuration allows the contact segments to be positioned closer to the gate structure, reducing drain-to-gate capacitance, while the segmentation itself creates thermal pathways that prevent heat accumulation in any single location
Solution Approach 2:
The segmented contact structure acts as an intermediary between the drain region and the gate, providing electrical connection while maintaining electrical isolation through gaps that also serve as thermal management features
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
The solution effectively reduces drain capacitance, improving the electrical performance and reliability of HEMTs by minimizing heat-related issues while maintaining adequate heat dissipation.
Implementation Method 1
The ohmic contact may include a gap or open space or defective region... using smaller, spaced terminal connections and a dielectric material to lower capacitance
Implementation Method 2
using smaller, spaced terminal connections and a dielectric material to lower capacitance
Implementation Method 3
Power amplifier High Electron Mobility Transistors (HEMTs) generate a large amount of heat that degrades electrical and reliability performance. The heat is generated under the gate
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to high-electron-mobility transistors and methods of manufacture. A structure includes: a semiconductor layer on a semiconductor material; a gate structure on the semiconductor layer; a drain region comprising the semiconductor layer and which is adjacent to the gate structure; an ohmic contact which includes at least one terminal connection connecting to the semiconductor material, the ohmic contact being adjacent to the drain region and spaced away from the gate structure; and a capacitance reducing structure adjacent to the drain region.