SiC Substrate Pit Contacts for Lower Electrical and Thermal Resistance
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Solution Overview
Problem
Silicon carbide (SiC) semiconductor power switching devices face limitations in reducing substrate resistance, which affects device performance and cost, as thinning the substrate below a certain thickness is impractical due to mechanical integrity issues.
Innovation Solution
A pattern of pits is etched partially through the SiC substrate, filled with ohmic metal to create low-resistance contacts, reducing both electrical and thermal resistance without compromising mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the substrate is thinned to reduce resistance, then electrical resistance decreases, but mechanical integrity deteriorates
Solution Approach 1:
The substrate surface is segmented into multiple pits distributed across the surface. Each pit creates a localized low-resistance contact region, and collectively these segmented regions reduce the overall substrate resistance without requiring thinning the entire substrate, thus maintaining mechanical integrity while improving electrical performance
Solution Approach 2:
Instead of uniformly thinning the entire substrate, the invention applies local modification by forming pits only in specific regions where low-resistance contacts are needed. The ohmic metal is placed locally within these pits, creating high-conductivity pathways only where required, preserving the mechanical strength of the bulk substrate while reducing resistance at critical contact points
2Reliability
If conventional thinning techniques are used to reduce substrate resistance, then electrical resistance decreases, but the substrate thickness becomes impractically thin
Solution Approach 1:
Instead of reducing resistance by decreasing substrate thickness in the vertical dimension, the invention transitions to a different dimensional approach by creating pits and filling them with conductive material. This lateral/dimensional approach to resistance reduction allows maintaining practical substrate thickness while achieving low resistance through alternative conduction pathways formed by the pit structures
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 effectively reduces substrate resistance below the limits of conventional thinning techniques, enhancing device performance and reducing manufacturing costs while maintaining mechanical integrity.
Implementation Method 1
an ohmic metal disposed at least in the pits to form low-resistance ohmic contacts
Implementation Method 2
The presence of the pattern of pits and ohmic contacts provides a reduced on resistance which improves the device operation
Data Source
AI summary
A power semiconductor device includes a silicon carbide substrate and has at least a first layer or region formed above the substrate. The silicon carbide substrate has a pattern of pits formed thereon. The power semiconductor device further includes an ohmic metal disposed at least in the pits to form low-resistance ohmic contacts. Each pit of the pattern of pits has a depth that extends short of the first layer.