SiC Semiconductor Source Electrode Mitigating Bias Temperature Instability
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Solution Overview
Problem
Silicon carbide (SiC) semiconductor devices face significant reliability and performance issues due to negative bias temperature instability (NBTI), which causes threshold voltage shifts, leading to devices becoming conductive without an applied gate-source voltage, and no industry-accepted solution exists to address this.
Innovation Solution
Incorporating a metal source electrode, such as indium or tantalum, in SiC semiconductor devices to limit threshold voltage shifts during operation, thereby mitigating NBTI effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metal source electrodes are used in SiC semiconductor devices, then device manufacturing is straightforward, but negative bias temperature instability causes significant threshold voltage shifts and reliability degradation
Solution Approach 1:
The patent applies composite materials by combining multiple metal layers (e.g., tungsten layer and copper layer) to form a composite source electrode structure. This composite structure leverages the properties of each metal: tungsten provides low diffusion coefficient to prevent metal diffusion into the semiconductor, while copper provides high electrical conductivity. This resolves the contradiction by achieving both reliability (through diffusion prevention) and electrical performance (through high conductivity), without requiring overly complex single-material solutions.
Solution Approach 2:
The patent uses an intermediary approach by introducing a specific metal layer (tungsten) as a barrier between the semiconductor substrate and the conductive metal layer (copper). This intermediary tungsten layer prevents direct interaction between copper and the semiconductor, blocking diffusion pathways while maintaining electrical connectivity. This resolves the reliability issue caused by metal diffusion without requiring complete structural redesign.
2Manufacturing precision
If the source electrode structure is simplified for ease of manufacture, then manufacturing precision may be compromised, leading to increased NBTI effects and threshold voltage instability
Solution Approach 1:
The composite metal layer structure (tungsten + copper) provides precise control over threshold voltage by preventing metal diffusion that would otherwise cause unpredictable threshold shifts. The tungsten barrier layer ensures consistent electrical properties over time and temperature, achieving manufacturing precision in threshold voltage control while using standard semiconductor fabrication processes for ease of manufacture.
Solution Approach 2:
The patent changes the material parameters of the source electrode by selecting specific metals with controlled diffusion coefficients and conductivities. By adjusting the thickness and composition of metal layers (e.g., 50nm tungsten, 100nm copper), the patent optimizes both threshold voltage stability and manufacturing feasibility, resolving the contradiction between precision and ease of manufacture.
Data Source
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AI summary
A semiconductor device (100) is disclosed along with methods (10) for manufacturing such a device. In certain embodiments, the semiconductor device includes a source electrode (124) formed using a metal that limits a shift, such as due to bias temperature instability, in a threshold voltage of the semiconductor device during operation. In certain embodiments the semiconductor device may be based on silicon carbide.