GaN Regrown Ohmic Contacts for RF Transistors
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Solution Overview
Problem
There is a need for semiconductor devices with manufacturable, high-performance, and reliable ohmic contacts and control electrodes, particularly for RF and high-speed applications using group-III nitride semiconductors, as existing solutions face challenges in achieving consistent and efficient contact formation.
Innovation Solution
The development of semiconductor devices with regrown ohmic contacts, specifically for GaN heterojunction field effect transistors, involves a process that includes forming a semiconductor substrate with epitaxially grown layers, creating isolation regions, and forming regrown source/drain regions and gate electrodes using dielectric layers and conductive caps, enabling efficient contact formation and improved device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ohmic contact formation methods are used, then manufacturing simplicity is maintained, but contact reliability and performance are insufficient
Solution Approach 1:
The patent applies preliminary action by forming a regrown semiconductor layer before final contact formation. The method includes forming a first opening in a dielectric layer, forming a regrown semiconductor layer over the substrate through the opening, and then forming the ohmic contact. This preliminary regrowth step prepares the contact region with improved crystalline structure and doping, enabling better contact reliability while managing complexity through structured process sequencing.
Solution Approach 2:
The patent segments the contact formation process into distinct stages: forming the first opening in the dielectric layer, forming the regrown semiconductor layer through the opening, and then forming the ohmic contact. This segmentation allows each step to be optimized independently, with the regrown layer serving as an intermediate structure that improves contact properties without requiring complete process redesign.
2Manufacturing precision
If regrown contacts are implemented, then contact performance and electron confinement are improved, but manufacturing process complexity increases
Solution Approach 1:
The regrown semiconductor layer is formed as a preliminary structure before final contact fabrication. This regrown layer provides a precisely controlled interface with improved crystalline quality and doping concentration, enabling manufacturing precision in contact formation. The process manages complexity by integrating this regrowth step into the existing fabrication sequence rather than adding entirely new process modules.
Solution Approach 2:
The patent utilizes parameter changes by controlling the regrowth conditions (temperature, doping concentration, layer thickness) to achieve optimal contact properties. The regrown semiconductor layer is formed with specific doping concentrations and thickness parameters that improve electron confinement and contact characteristics, demonstrating how parameter optimization resolves the trade-off between precision and complexity.
3Reliability
If intimate contact between regrown regions and substrate is achieved, then electron confinement and modulation capabilities improve, but process difficulty increases
Solution Approach 1:
The regrown semiconductor layer is formed in advance to create the intimate contact interface between the contact region and substrate. This preliminary regrowth ensures proper crystalline alignment and doping distribution, achieving superior electron confinement capability. The process maintains manufacturability by using standard epitaxial growth techniques that are already integrated into group-III nitride fabrication workflows.
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 approach results in semiconductor devices with enhanced contact reliability and performance, suitable for high-speed and RF applications, by ensuring intimate contact between the regrown regions and the semiconductor substrate, thereby improving electron confinement and modulation capabilities.
Implementation Method 1
forming a regrown semiconductor layer over the semiconductor substrate through the first opening
Data Source
AI summary
An embodiment of a semiconductor device includes a semiconductor substrate that includes a channel, a first dielectric layer disposed over the semiconductor substrate, and a regrown contact formed through a first opening in the first dielectric layer. The regrown contact includes a regrown region formed over the semiconductor substrate, an overhang region coupled to the regrown region and formed over the first dielectric layer, adjacent the first opening, and a conductive cap formed over the regrown region and the overhang region. A method for fabricating the semiconductor device includes forming the first dielectric layer over the semiconductor substrate, forming the first opening in the first dielectric layer, forming a regrown semiconductor layer within the first opening and over the first dielectric layer, forming a conductive cap over the regrown semiconductor layer, and etching the regrown semiconductor layer outside the conductive cap.