Composite Contact Reduces Impedance in Semiconductor Devices
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Solution Overview
Problem
High contact resistance in semiconductor devices, particularly in wide bandgap materials, limits their performance, and existing annealing techniques lead to morphology degradation and increased resistance at high frequencies.
Innovation Solution
A composite contact structure incorporating a DC conducting electrode and a capacitive electrode that extends beyond the DC electrode, providing combined resistive-capacitive coupling to reduce impedance at high frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature annealing is used to reduce contact resistance, then contact resistance decreases, but morphology degradation and defect generation increase
Solution Approach 1:
The contact structure is segmented into multiple functional layers: a first contact layer (Ti/Al) providing mechanical adhesion and initial contact, and a second contact layer (Au/Ge/Ni) providing low resistance path. This segmentation allows each layer to be optimized for its specific function without requiring excessive annealing temperature, thus reducing morphology degradation while maintaining low contact resistance
Solution Approach 2:
The invention uses composite contact structures combining different materials (Ti/Al/Au/Ge/Ni) with complementary properties. The Ti/Al layer provides strong adhesion to GaN, while the Au/Ge/Ni layer provides low resistance. This composite approach enables effective contact formation at lower annealing temperatures compared to single-material contacts, thereby reducing thermal damage to the contact morphology
2Reliability
If annealing temperature is increased to achieve lower contact resistance in wide bandgap materials, then contact resistance decreases, but contact edge roughness increases
Solution Approach 1:
By dividing the contact into multiple deposited layers (Ti/Al followed by Au/Ge/Ni), each layer can be formed at controlled temperatures with precise thickness control. This segmentation prevents the need for high-temperature annealing that would cause edge roughness, while still achieving low contact resistance through the optimized multi-layer structure
Solution Approach 2:
The invention changes the material composition parameters of the contact layers rather than relying on temperature parameters. By selecting materials with appropriate work functions and diffusion properties (Ti, Al, Au, Ge, Ni), low contact resistance is achieved through material selection rather than thermal activation, thereby avoiding contact edge roughness
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 composite contact structure significantly reduces contact impedance at high frequencies, improving the performance of semiconductor devices by minimizing access resistance and enabling alignment-free fabrication.
Implementation Method 1
a direct current (DC) conducting electrode attached to a semiconductor layer in the device
Implementation Method 2
a capacitive electrode that is partially over the DC conducting electrode and extends beyond the DC conducting electrode
Implementation Method 3
The composite contact provides a combined resistive-capacitive coupling to the semiconductor layer. As a result, a contact impedance is reduced when the corresponding semiconductor device is operated at high frequencies
Data Source
AI summary
A composite contact for a semiconductor device is provided. The composite contact includes a DC conducting electrode that is attached to a semiconductor layer in the device, and a capacitive electrode that is partially over the DC conducting electrode and extends beyond the DC conducting electrode. The composite contact provides a combined resistive-capacitive coupling to the semiconductor layer. As a result, a contact impedance is reduced when the corresponding semiconductor device is operated at high frequencies.