Power MOSFET Super Junction Structure for Breakdown Voltage
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Solution Overview
Problem
Existing semiconductor devices with super junction structures face challenges in achieving both low conduction resistance and high junction breakdown voltage, particularly in the outer peripheral parts, where existing methods often require complex manufacturing processes and do not consistently deliver stable results.
Innovation Solution
A semiconductor device is designed with a p-type epitaxial layer on an n-type substrate, featuring trenches that define active regions and a drain offset layer, along with a channel region connected by p-type and n-type diffusion regions, allowing for a simple manufacturing method that achieves low conduction resistance and high breakdown voltage without adding complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer peripheral part is formed with the same conductivity type as the conduction layer and lower impurity concentration, then high breakdown voltage is obtained, but conduction resistance increases
Solution Approach 1:
The patent applies local quality by forming a p-type diffusion region specifically in the outer peripheral part of the epitaxial layer, creating a localized p-type region that terminates electric field lines. This local modification allows the outer peripheral part to have different electrical properties (p-type conductivity) from the main active region, enabling high breakdown voltage at the periphery without compromising the low conduction resistance in the active super junction cells.
2Reliability
If various methods are used to obtain high breakdown voltage in the outer peripheral part, then breakdown voltage improves, but manufacturing complexity increases
Solution Approach 1:
The patent merges the formation of the p-type diffusion region in the outer peripheral part with the existing manufacturing processes for forming the super junction structure. The p-type diffusion is performed using the same ion implantation or diffusion steps already required for creating the p-n junction cells, thereby achieving high breakdown voltage in the outer peripheral part without adding separate manufacturing steps or increasing process complexity.
3Reliability
If the outer peripheral part uses non-super junction structure, then high breakdown voltage is achieved, but conduction resistance cannot be reduced
Solution Approach 1:
The patent applies local quality by confining the p-type diffusion region to only the outer peripheral part of the epitaxial layer, while maintaining the super junction structure (alternating n-type and p-type columns) in the active region. This localized approach allows the outer peripheral part to provide high breakdown voltage through field termination, while the active region maintains low conduction resistance through the super junction configuration, thus resolving the contradiction between these two requirements.
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 enables a semiconductor device with both low conduction resistance and high junction breakdown voltage, improving performance and simplifying the manufacturing process by optimizing the impurity concentration and structure of the epitaxial layer and diffusion regions.
Implementation Method 1
an n-type diffusion region that functions as a drain offset layer of a power MOSFET is formed, and, in the epitaxial layer between the side wall of the trench and the n-type diffusion region, a p-type diffusion region connected with a channel region of the power MOSFET is formed
Data Source
AI summary
To realize a semiconductor device having a power MOSFET satisfying both a low conduction resistance and a high junction breakdown voltage by a simple and easy manufacturing method. Over an n-type substrate, a p-type epitaxial layer of a low concentration is formed, and, in an active part, a plurality of active regions is defined by a plurality of trenches that is formed in the epitaxial layer and extends in a first direction with first intervals in a second direction orthogonal to the first direction. In the epitaxial layer between the adjacent trenches, an n-type diffusion region that functions as a drain offset layer is formed, and, in the epitaxial layer between a side wall of the trench and the n-type diffusion region, a p-type diffusion region connected with a channel region (the p-type diffusion region) is formed, to constitute a super junction structure. Further, by forming an n-type diffusion region in the epitaxial layer, having a prescribed width from a side wall of a trench lying in the end part of the active part toward an outer periphery part, to achieve the improvement of a drain breakdown voltage.