Guard Ring Diffusion Profile for Depletion Layer Control
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Solution Overview
Problem
Existing semiconductor devices face challenges in controlling the spread of the depletion layer in peripheral areas and achieving high breakdown voltage due to limitations in guard ring properties, which are influenced by the impurity regions within the substrate.
Innovation Solution
The semiconductor device incorporates guard rings of a second conductivity type with a diffusion region wider at the top, forming a superjunction structure that promotes the spread of the depletion layer and increases breakdown voltage, along with specific resistance and impurity concentration optimization to distribute the electric field effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If guard rings are formed at the same time as the impurity region within the cell area, then the manufacturing process becomes more efficient, but the properties of the guard rings are limited by the properties of the impurity region and it becomes difficult to control the spread of the depletion layer in the peripheral area
Solution Approach 1:
The patent applies local quality by creating different diffusion region configurations for guard rings in the peripheral area versus impurity regions in the cell area. Specifically, the guard rings include at least one first ring with a diffusion region wider at the top, while other guard rings have uniform diffusion regions. This local differentiation allows precise control of depletion layer spread in the peripheral area while maintaining manufacturing efficiency through simultaneous formation with cell area structures.
2Device complexity
If guard rings with uniform properties are used in the peripheral area, then the device structure remains simple, but the breakdown voltage in the peripheral area cannot be sufficiently increased
Solution Approach 1:
The patent applies parameter changes by varying the diffusion region width in guard rings to optimize breakdown voltage. At least one first ring among the guard rings has a diffusion region that is wider at the top, which promotes the spread of the depletion layer toward the end face of the semiconductor layer. This parameter variation increases the breakdown voltage in the peripheral area while maintaining reasonable structural complexity.
3Reliability
If the diffusion region of guard rings is made wider at the top, then the depletion layer spread is promoted and breakdown voltage increases, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies partial action by implementing the wider-at-top diffusion region configuration in at least one first ring among the guard rings, rather than requiring all guard rings to have this configuration. This partial implementation achieves the necessary depletion layer spread and breakdown voltage increase while reducing the overall manufacturing precision burden compared to requiring all guard rings to have the complex structure.
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 design allows for precise control of the depletion layer spread and significantly increases breakdown voltage in both peripheral and cell areas, providing a reliable high withstand voltage element.
Implementation Method 1
it is possible to promote the spread of the depletion layer toward an end face of the semiconductor layer via the first ring
Implementation Method 2
appropriate design of the degree to which the depletion layer spreads toward the end face enables an increase in breakdown voltage in the peripheral area
Data Source
AI summary
A semiconductor device that includes: a semiconductor layer of a first conductivity type, having a peripheral area and a cell area inside of the peripheral area; a region of a second conductivity type in the semiconductor layer in the cell area; and a plurality of guard rings of the second conductivity type in the semiconductor layer in the peripheral area, each having a substantially same depth as the region of the second conductivity type in the cell area. The plurality of guard rings include at least one first ring that has a diffusion region in the depth profile in the semiconductor layer that is wider at a top thereof.