Guarding Ring Structure with Embedded N-Type Rings for High Voltage Devices
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Solution Overview
Problem
Conventional high voltage semiconductor power devices require extensive guarding ring structures to achieve desired breakdown voltages, leading to increased area and design time due to inefficient electric field distribution, where more rings are needed to achieve higher voltages, and the ring spacing is not fully utilized.
Innovation Solution
A guarding ring structure for semiconductor power devices featuring a lightly doped N type epitaxial layer and N type diffusion rings embedded in P+ type diffusion rings, altering the electric field distribution from triangular to trapezoidal, allowing for reduced ring spacing or number while maintaining withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional field limiting ring structure with P+ type diffusion rings is used, then the manufacturing process is simple without additional photoetching steps, but the electric field distribution forms a triangle profile which is not fully utilized, requiring more rings and larger area to achieve the same withstand voltage
Solution Approach 1:
The patent changes the doping concentration parameter by introducing a lightly doped N type epitaxial layer with doping concentration lower than the substrate, and modifies the electric field distribution shape from triangular to trapezoidal through the addition of N type diffusion rings embedded in P+ type diffusion rings, thereby improving the utilization of ring spacing and reducing the required guarding ring area
Solution Approach 2:
The patent creates a composite structure by embedding N type diffusion rings within P+ type diffusion rings, forming a multi-layered composite guarding ring structure that combines different doping types and concentrations to achieve optimized electric field distribution and reduced area
2Reliability
If more P+ type diffusion rings are added to increase withstand voltage, then the breakdown voltage requirement is met, but the device complexity and design time increase
Solution Approach 1:
The patent changes the electric field distribution shape from triangular to trapezoidal through parameter modifications in doping concentration and structure configuration, enabling fewer rings to achieve the same withstand voltage and thus reducing device complexity while maintaining reliability
3Area of stationary object
If the ring spacing is reduced to decrease the number of rings, then the guarding ring area is reduced, but the electric field distribution is not optimized and withstand voltage may be compromised
Solution Approach 1:
The composite structure of embedded N type diffusion rings in P+ type diffusion rings creates a trapezoidal electric field distribution that optimizes the utilization of ring spacing, allowing reduced ring spacing without compromising withstand voltage, thereby reducing guarding ring area 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
This approach enables the same withstand voltage to be achieved with less guarding ring area and reduced design time by optimizing each ring spacing, effectively utilizing the ring area more efficiently and reducing the number of rings required.
Implementation Method 1
the small radius of the junction curvature may cause electric field intensity, thereby making the breakdown voltage far below the planar junction breakdown voltage
Implementation Method 2
The PN junction refers to a space charge region formed at the interface between the P-type and N-type semiconductor materials inside a same semiconductor substrate (usually a silicon substrate or a germanium substrate) by doping and diffusion of dopants
Data Source
AI summary
The present invention provides a guarding ring structure of a semiconductor high voltage device and the manufacturing method thereof. The guarding ring structure comprises a first N type monocrystalline silicon substrate (3), a second N type monocrystalline silicon substrate (8), a discontinuous oxide layer (2), a metal field plate (1), a device region (9), multiple P+ type diffusion rings (5) and an equipotential ring (4). The second N type monocrystalline silicon substrate (8) is a single N type crystalline layer epitaxially formed on the first N type monocrystalline silicon substrate (3) and has lower doping concentration than the first N type monocrystalline silicon substrate (3). N type diffusion rings (6) are embedded in the inner side of the P+ type diffusion rings (5) and are fully depleted at zero bias voltage. The guarding ring structure can achieve the same withstand voltage with less area and design time.