Semiconductor Field Electrode Contact Structure for On-State Resistance
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Solution Overview
Problem
Power semiconductor devices, such as IGFETs and IGBTs, face challenges in reducing switching losses due to the limitations in dopant concentrations in the drift zone, which affect the on-state resistance and blocking capabilities.
Innovation Solution
The semiconductor device incorporates a field electrode structure with a field dielectric, a transistor section with a source zone, a drift zone, and a body zone, along with a gate structure and contact structures that minimize horizontal hole current paths to reduce the risk of parasitic BJT ignition, thereby enhancing avalanche ruggedness and reducing on-state resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If higher dopant concentrations are used in the drift zone, then on-state resistance is reduced, but blocking capabilities are adversely impacted
Solution Approach 1:
The drift zone is divided into multiple sections with different dopant concentrations. The first drift zone section has a higher dopant concentration to reduce on-state resistance, while the second drift zone section has a lower dopant concentration to maintain blocking capabilities. This segmentation allows each zone to be optimized for its specific function.
Solution Approach 2:
Different regions of the drift zone are assigned different dopant concentrations based on their functional requirements. The region closer to the source zone (first drift zone section) has higher doping to reduce resistance, while the region closer to the drain zone (second drift zone section) has lower doping to enhance blocking capability. This local quality variation resolves the contradiction between low resistance and high blocking capability.
2Reliability
If longer horizontal hole current paths are present, then parasitic BJT ignition risk increases, but device complexity increases
Solution Approach 1:
The contact structure is designed to directly adjoin both the source zone and the body zone, effectively extracting or removing the horizontal hole current path that would otherwise exist through the drift zone. This direct adjunction eliminates the need for complex additional structures to control hole paths, as the contact structure itself serves this function.
Solution Approach 2:
The contact structure performs multiple functions: it provides electrical contact to both the source and body zones simultaneously, and it serves to minimize horizontal hole current paths to prevent parasitic BJT ignition. This multi-functionality reduces device complexity by combining what could have been separate structures into one integrated contact structure.
3Loss of energy
If switching losses are reduced, then energy efficiency improves, but device performance may be compromised
Solution Approach 1:
The dopant concentration parameter is changed across different sections of the drift zone. By increasing the dopant concentration in the first drift zone section, the on-state resistance is reduced, which directly reduces conduction losses and improves energy efficiency during switching operations, while the second drift zone section maintains lower doping to preserve blocking capabilities.
Data Source
AI summary
A semiconductor device includes a field electrode structure with a field electrode and a field dielectric surrounding the field electrode. A semiconductor body includes a transistor section surrounding the field electrode structure and including a source zone, a first drift zone section and a body zone separating the source zone and the first drift zone section. The body zone forms a first pn junction with the source zone and a second pn junction with the first drift zone section. A gate structure surrounds the field electrode structure and includes a gate electrode and a gate dielectric separating the gate electrode and the body zone. A contact structure directly adjoins the source and body zones and surrounds the field electrode structure equably with respect to the field electrode structure.