Fragmented Ohmic Contacts for HEMT Design Flexibility
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Solution Overview
Problem
The manufacture of high-electron-mobility transistors (HEMTs) faces challenges in creating low resistance ohmic contacts, particularly due to the need for precise metal alloy composition and high-temperature annealing, which limits design flexibility and requires extensive redesigning of the metal deposition process.
Innovation Solution
A fragmented ohmic contact structure is introduced, where the ohmic contact is split into multiple sections with increased perimeter-to-area ratio, allowing for local control of alloy composition without altering the metal deposition process, by forming trenches in the dielectric and semiconductor layers and filling them with a metal stack that anneals to form a specific alloy composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional ohmic contact structure with a single metal stack is used, then the contact can provide low resistance, but the manufacturing process requires precise control of metal alloy composition and high-temperature annealing, which limits design flexibility and requires extensive redesigning
Solution Approach 1:
The ohmic contact is divided into multiple discrete metal contact fragments instead of using a single continuous metal stack. Each fragment can be independently formed in trenches, allowing different compositions and annealing conditions for different contacts on the same chip, thereby improving design flexibility while maintaining low resistance through optimized local alloy formation
2Reliability
If high-temperature annealing is used to form the required metal alloy composition, then low resistance ohmic contact is achieved, but the manufacturing process becomes complex and requires extensive redesigning of the metal deposition process
Solution Approach 1:
Different regions of the chip can have metal contact fragments with different alloy compositions formed by selective annealing. The annealing process is applied locally to specific trench regions rather than uniformly across the entire chip, allowing optimization of each contact's resistance characteristics independently while simplifying the overall manufacturing process
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 enhances current flow efficiency, allows for multiple contacts with different compositions on the same chip, and optimizes contact design without changing the established metal deposition process, thereby improving the performance and flexibility of HEMT manufacturing.
Implementation Method 1
high temperature annealing
Implementation Method 2
During annealing a chemical reaction between the ohmic metal stack and semiconductor takes place providing a low resistance ohmic contact
Implementation Method 3
a metallic connector layer electrically connecting the metal contact fragments
Data Source
AI summary
A semiconductor arrangement including a substrate, a dielectric layer, and a semiconductor layer disposed between the substrate and the dielectric layer. The arrangement further includes an ohmic contact including a plurality of metal contact fragments located in a plurality of trenches formed in the dielectric layer, and a metallic connector layer electrically connecting the metal contact fragments. The ohmic contact electrically connects the metallic connector layer to the semiconductor layer.