Power Diode Junction Structure for High Breakdown in Smaller Dies
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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 limited by guard ring number and area occupancy, which affects electrical performance and manufacturing cost.
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 limitations of guard rings, allowing for reduced device size and lower manufacturing costs.
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 thin thickness
Solution Approach 1:
The patent transitions from a conventional planar mesa structure to a three-dimensional protruding structure where the termination region extends vertically beyond the active region. This dimensional change allows the termination structure to provide mechanical support without reducing the active region thickness, thereby maintaining wafer strength while achieving proper structural definition.
Solution Approach 2:
The patent employs a composite structure combining different doped regions (n-type active region, p-type termination region, and n-type drift region) in a vertical stack. This composite arrangement creates a multi-functional structure where each layer contributes differently to both mechanical strength and electrical performance, with the thicker termination region providing structural support.
2Reliability
If guard rings are increased to increase breakdown voltage in high voltage power diodes, then the breakdown voltage is improved, but the device area increases and manufacturing cost increases
Solution Approach 1:
The patent moves the electric field management from a two-dimensional planar guard ring approach to a three-dimensional vertical structure. The protruding termination region with its extended depth creates additional field control in the vertical dimension, achieving high breakdown voltage without requiring multiple lateral guard rings that would increase device area.
Solution Approach 2:
The patent changes the geometric parameters of the termination region by extending its depth beyond the active region and adjusting the doping concentration gradient. This parameter modification allows the termination structure to provide both mechanical support and electrical field control, achieving high breakdown voltage in a more compact area compared to conventional guard ring approaches.
3Reliability
If guard rings are increased to increase breakdown voltage, then the breakdown voltage is improved, but the manufacturing cost increases
Solution Approach 1:
The patent achieves high breakdown voltage through a vertical three-dimensional structure rather than multiple lateral guard rings. This dimensional transformation simplifies the manufacturing process by requiring fewer photolithography steps and doping zones, thereby reducing manufacturing cost while maintaining or improving breakdown voltage performance.
Solution Approach 2:
The patent optimizes the doping concentration and geometric parameters of the termination region to achieve high breakdown voltage in a single integrated structure. This parameter optimization reduces the number of manufacturing steps compared to multiple guard rings, lowering process complexity and manufacturing cost.
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 die size and manufacturing complexity, making it suitable for high-voltage applications.
Implementation Method 1
forming a heavily doped region of the second conductivity type in the second diffusion layer. The heavily doped region has a first surface and a second surface opposite to the first surface of the heavily doped region. The second surface of the heavily doped region is coplanar with the second surface of the second diffusion layer, and the heavily doped region extends toward the core layer such that the first surface of the heavily doped region reaches the second surface of the core layer
Data Source
Figure 1
Figure 2A
Figure 2B
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.