Power Diode Junction Termination for High Breakdown Voltage
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Solution Overview
Problem
Conventional power diodes with mesa or planar structures face challenges in achieving high breakdown voltage and structural strength, with mesa structures being weak and planar structures requiring multiple guard rings that increase manufacturing costs and device size.
Innovation Solution
A power diode device with a substrate structure comprising a core layer and diffusion layers of different conductivity types, where a heavily doped region forms a PN junction with the core layer, enhancing structural strength and electric field distribution without the need for multiple guard rings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a mesa structure is used to define active region and junction termination, then the structural definition is achieved, but the wafer strength is reduced due to thinning of the upper half of the substrate
Solution Approach 1:
The patent inverts the conventional mesa structure by forming the termination region at the bottom surface of the substrate rather than the top surface. This allows the upper half of the substrate to remain thick and strong while the etching and mesa formation occur at the bottom surface, thereby maintaining wafer strength while achieving proper structural definition.
2Ease of manufacture
If the gradient of the side surface of the mesa is not precisely controlled during etching, then the manufacturing process is simpler, but the breakdown voltage is insufficient
Solution Approach 1:
By performing the etching process at the bottom surface to create the termination region, the patent avoids the need for precise gradient control of side surfaces during etching. The inverted approach allows for more tolerant etching parameters while still achieving the required breakdown voltage characteristics.
3Reliability
If multiple guard rings are added to increase breakdown voltage in high voltage power diodes, then the breakdown voltage increases, but the device size increases and manufacturing cost increases
Solution Approach 1:
The patent eliminates the need for multiple guard rings by inverting the termination structure to the bottom surface. This single inverted termination region achieves the breakdown voltage enhancement that would otherwise require multiple guard rings, thereby reducing device area and simplifying the manufacturing process.
4Reliability
If multiple guard rings are added to increase breakdown voltage, then the breakdown voltage increases, but the manufacturing cost increases
Solution Approach 1:
By inverting the termination region to the bottom surface, the patent achieves high breakdown voltage without requiring multiple guard rings. This reduces the number of photomask steps and processing complexity, thereby lowering manufacturing cost while maintaining reliability.
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
The solution improves wafer strength, breakdown voltage, and terminal length while reducing device size and manufacturing costs, making it suitable for high-voltage applications.
Implementation Method 1
diffusing the heavily doped region towards the core layer to form a first PN junction between the heavily doped region and the core layer
Data Source
AI summary
A power diode device includes a substrate. The substrate includes a core layer of a first conductive type, a first diffusion layer of the first conductive type, a second diffusion layer of a second conductive type, and a heavily doped region of the second conductive type. The core layer is located between the first diffusion layer and the second diffusion layer. A thickness of the core layer is greater than that of the second diffusion layer. The heavily doped region is located in the second diffusion layer and extends toward the core layer to form a PN junction between the heavily doped region and the core layer. A method for manufacturing the power diode device is also provided.