Superjunction Semiconductor Device Termination Structure Optimization
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Solution Overview
Problem
Conventional superjunction semiconductor devices face challenges in maintaining high breakdown voltage while minimizing on-resistance, as reducing the n-type drift layer thickness to lower on-resistance leads to decreased breakdown voltage, and increasing it to enhance breakdown voltage increases on-resistance, creating a tradeoff relationship.
Innovation Solution
The superjunction semiconductor device incorporates a parallel pn structure with p-type and n-type column regions alternately arranged, where the impurity concentration and width of these columns are optimized in the active and termination regions to balance charge and reduce electric field concentration near the channel stopper, thereby enhancing breakdown voltage without increasing on-resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the thickness of the n-type drift layer is reduced, then the on-resistance is reduced, but the breakdown voltage decreases
Solution Approach 1:
The drift layer is segmented into alternating p-type column regions and n-type column regions, forming a parallel pn structure. This segmentation allows the n-type regions to carry current (reducing on-resistance) while the p-type regions create depletion zones that sustain breakdown voltage during off-state operation.
Solution Approach 2:
Different regions of the drift layer are assigned different conductivity types (p-type or n-type) to perform different functions. The n-type column regions provide low resistance for current conduction, while the p-type column regions create wide depletion layers for voltage sustenance, optimizing both on-resistance and breakdown voltage locally.
2Reliability
If the thickness of the n-type drift layer is increased, then the breakdown voltage is increased, but the on-resistance increases
Solution Approach 1:
Instead of using a uniform thick n-type drift layer, the structure is segmented into alternating p-type and n-type column regions. The n-type regions are made thinner than a conventional drift layer would require, but the overall breakdown voltage is maintained through the cumulative effect of multiple depletion layers formed at the pn junctions.
Solution Approach 2:
The drift layer is constructed as a composite structure with alternating p-type and n-type semiconductor regions. This composite parallel pn structure combines the voltage-blocking capability of wide depletion layers with the low resistance of thin n-type regions, achieving both high breakdown voltage and low on-resistance.
3Reliability
If the impurity concentration in the p-type column regions is increased, then the breakdown voltage is enhanced, but the electric field concentration increases
Solution Approach 1:
The impurity concentration is optimized locally in each p-type column region to create an appropriate balance between depletion layer width and electric field distribution. By controlling the impurity concentration in the p-type regions, the depletion layer extends sufficiently to sustain voltage while avoiding excessive electric field concentration that would cause premature breakdown.
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 effectively mitigates electric field concentration and maintains high breakdown voltage even at high temperatures, suppressing breakdown voltage decreases and ensuring reliable operation under varying conditions.
Implementation Method 1
during an off state, a depletion layer spreads to the n-type drift layer, which has a high resistance, and thus, the depletion layer has a function of sustaining the breakdown voltage
Implementation Method 2
a voltage withstanding structure is formed... This configuration effectively mitigates electric field concentration and maintains high breakdown voltage
Implementation Method 3
an impurity amount contained by the p-type column regions and an impurity amount contained by the n-type column regions are substantially equal, whereby in the off state, a pseudo non-doped layer is created
Data Source
AI summary
A superjunction semiconductor device having a termination structure portion surrounding an active region in a plan view. The device includes: a semiconductor substrate; a first semiconductor layer provided on the semiconductor substrate; and a parallel pn structure and a channel stopper provided in the first semiconductor layer. The channel stopper surrounds the parallel pn structure in the plan view, and contacts the parallel pn structure in the termination structure portion. The parallel pn structure includes a plurality of first columns each having a first width and a plurality of second columns each having a second width that repeatedly alternate one another parallel to the main surface. In a region of the parallel pn structure contacting the channel stopper, a product of the second width and an impurity concentration of the second columns is less than a product of the first width and an impurity concentration of the first columns.