Stripe Cell Power Semiconductor Guard Ring Design
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Solution Overview
Problem
The non-uniform distribution of the electrical field around the active area and the compromised voltage tolerance of the guard ring structure in power semiconductor devices with stripe cell geometry due to the presence of poly-silicon gate buses, leading to poor performance and reduced break-down voltage.
Innovation Solution
A power semiconductor device design featuring striped gate conductive structures and a guard ring structure formed on the same conductive layer, with the striped gate conductive structures electrically connected to the ring-shaped conductive structures through a gate metal pad, ensuring uniform electric field distribution and eliminating breaches that affect voltage tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If poly-silicon gate buses are used in stripe cell geometry, then the device can be manufactured with standard processes, but the electrical field distribution becomes non-uniform and break-down voltage decreases
Solution Approach 1:
The patent extracts the gate bus structure from the poly-silicon layer and places it in a separate dedicated layer, removing the harmful interaction between gate buses and guard rings. This allows the gate bus to be positioned without creating breaches in the guard ring structure, thereby maintaining uniform electrical field distribution and high break-down voltage while preserving manufacturability through standard multi-layer processing.
Solution Approach 2:
The patent moves the gate bus from the same plane as the guard rings (2D constraint) to a different layer (3D solution). By utilizing the vertical dimension with separate conductive layers, the gate bus can extend across the device without intersecting or breaching the guard ring structure, eliminating the electrical field distortion caused by planar intersections.
2Ease of operation
If poly-silicon gate buses are used in stripe cell geometry, then gate voltage can be distributed, but breaches are formed in ring-shaped doped regions reducing voltage tolerance
Solution Approach 1:
The patent segments the gate voltage distribution function into two separate components: the poly-silicon gate electrodes in one layer and the gate bus in a separate layer. This segmentation allows the gate bus to distribute voltage without physically breaching the guard ring structure, as the two functions operate in spatially separated layers, maintaining both voltage distribution capability and structural integrity.
Solution Approach 2:
The patent introduces a separate conductive layer as an intermediary between the gate bus and the guard ring structure. This intermediate layer allows electrical connection for gate voltage distribution without the gate bus physically intersecting or breaching the ring-shaped doped regions, thereby maintaining voltage tolerance while enabling voltage distribution.
3Reliability
If striped gate conductive structures are used, then Miller capacitance is improved, but electrical field distribution becomes non-uniform
Solution Approach 1:
The patent applies partial action by positioning the gate bus to connect only to specific points on the guard ring structure rather than continuously intersecting it. The gate bus extends beyond what is strictly necessary for electrical connection, allowing optimal positioning that maintains uniform electrical field distribution while still providing sufficient gate voltage distribution for improved Miller capacitance.
Data Source
AI summary
A power semiconductor device of stripe cell geometry including a substrate, a plurality of striped power semiconductor units, and a guard ring structure is provided. The substrate has an active area and a termination area surrounding the active area defined thereon. The striped semiconductor unit includes a striped gate conductive structure. The striped semiconductor units are located in the active area. The guard ring structure is located in the termination area and includes at least a ring-shaped conductive structure surrounding the striped power semiconductor units. The ring-shaped conductive structure and the striped gate conductive structures are formed on the same conductive layer, and at least one of the striped gate conductive structures is separated from the nearby ring-shaped conductive structure and electrically connected to the nearby ring-shaped conductive structure through the gate metal pad.