Superjunction Semiconductor Device Peripheral Structure
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Solution Overview
Problem
Superjunction semiconductor devices face a trade-off between breakdown voltage characteristics and voltage drop characteristics, and their charge resistance is insufficient for resin mold seal structures, leading to potential drops in breakdown voltage reliability.
Innovation Solution
The device incorporates parallel pn layers with a smaller repeating pitch in the peripheral portion and a surface layer with lower impurity concentration, along with reduced depth of p-type partition regions in the outer peripheral portion, to enhance charge resistance and prevent depletion layer overspreading, especially under negative surface charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the drift layer impurity concentration is increased to reduce on-resistance, then voltage drop characteristics improve, but breakdown voltage decreases
Solution Approach 1:
The drift layer is segmented into multiple thin drift regions separated by partition regions, creating a parallel pn layer structure. Each segment has small width allowing complete depletion at low voltage, while the series connection of multiple segments achieves high breakdown voltage. This segmentation enables the drift layer to have higher overall impurity concentration (lower on-resistance) while maintaining high breakdown voltage through the segmented architecture.
Solution Approach 2:
The patent applies different impurity concentrations to different regions: the drift regions have higher impurity concentration to reduce on-resistance, while the partition regions have alternating conductivity types. This local differentiation of properties allows simultaneous optimization of both voltage drop and breakdown voltage characteristics that cannot be achieved with a uniform structure.
2Reliability
If the repeating pitch of parallel pn layers in the peripheral portion is reduced to improve charge resistance, then device complexity increases
Solution Approach 1:
The patent implements local quality by applying the smaller repeating pitch only to the element peripheral portion where charge resistance is needed, while the element active portion maintains the larger first repeating pitch. This localized approach improves charge resistance without unnecessarily complicating the entire device structure, optimizing the trade-off between performance and complexity.
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 configuration significantly improves charge resistance and long-term breakdown voltage reliability, even under high surface charge conditions, such as those encountered in resin mold seal environments.
Implementation Method 1
when the depletion layer spreads from the pn junction between each region in the parallel pn structure when turning off, each region of the parallel pn structure is of a width small enough to be completely depleted at a low withstand voltage
Implementation Method 2
a depletion layer caused by a reverse bias voltage applied to a main junction when turning off extends in the vertical direction between the main surfaces
Implementation Method 3
The electrical field concentration reduction function is a function that reduces the electrical field concentration which is liable to occur at the drift layer terminal when applying an off-state voltage, thus preventing a low breakdown voltage breakdown
Implementation Method 4
Charge resistance is a function that prevents a drop in breakdown voltage reliability, wherein a charge applied to the surface affects the extension of the depletion layer below the surface, and the breakdown voltage decreases along with the passing of time
Data Source
AI summary
A superjunction semiconductor device is disclosed in which the trade-off relationship between breakdown voltage characteristics and voltage drop characteristics is considerably improved, and it is possible to greatly improve the charge resistance of an element peripheral portion and long-term breakdown voltage reliability. It includes parallel pn layers of n-type drift regions and p-type partition regions in superjunction structure. PN layers are depleted when off-state voltage is applied. Repeating pitch of the second parallel pn layer in a ring-like element peripheral portion encircling the element active portion is smaller than repeating pitch of the first parallel pn layer in the element active portion. Element peripheral portion includes low concentration n-type region on the surface of the second parallel pn layer. The depth of p-type partition region of an outer peripheral portion in the element peripheral portion is smaller than the depth of p-type partition region of an inner peripheral portion.