Superjunction Semiconductor Peripheral Section Electric Field Relaxation
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Solution Overview
Problem
Conventional superjunction semiconductor devices face challenges in achieving high breakdown voltage and avalanche withstanding capability due to the tradeoff between on-resistance and breakdown voltage, particularly in the peripheral sections where avalanche breakdown occurs, limiting the current that can be handled before device breakdown.
Innovation Solution
The semiconductor device incorporates a vertical drift section with alternating conductivity type layers and a peripheral section structured with narrower pitch and higher impurity concentration in the p-type regions, along with a channel stopper region and field plate electrode, to relax the electric field and enhance avalanche withstanding capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the n-type drift layer is made thinner to reduce on-resistance, then the on-resistance decreases, but the breakdown voltage decreases because the depletion layer width is reduced and electric field strength reaches critical level sooner
Solution Approach 1:
The drift layer is segmented into alternating n-type and p-type regions (superjunction structure). This segmentation allows the depletion layers from pn-junctions to expand laterally and deplete the entire drift layer, achieving high breakdown voltage even with heavily doped regions that reduce on-resistance.
Solution Approach 2:
Different regions of the drift layer have different conductivity types (n-type and p-type alternating). The n-type regions provide low resistance for current flow, while the p-type regions enable depletion layer formation for high breakdown voltage. This local quality differentiation resolves the tradeoff between on-resistance and breakdown voltage.
2Reliability
If the n-type drift layer is made thicker to increase breakdown voltage, then the breakdown voltage increases, but the on-resistance increases resulting in large losses
Solution Approach 1:
The drift layer is divided into alternating n-type and p-type regions. This segmentation enables the depletion layers to expand laterally from the pn-junctions, depleting the entire drift layer thickness and achieving high breakdown voltage without requiring a uniformly thick low-doped layer, thus reducing on-resistance.
Solution Approach 2:
The alternating conductivity type regions create local variations where n-type regions provide low resistance paths while p-type regions enable depletion formation. This local quality differentiation allows simultaneous achievement of low on-resistance and high breakdown voltage.
3Ease of manufacture
If no peripheral structure is provided to simplify device structure, then manufacturing is simpler, but the breakdown voltage is low in the peripheral portions
Solution Approach 1:
The alternating conductivity type structure is extended into the peripheral sections, creating a segmented pattern of n-type and p-type regions around the active area. This segmentation enables the peripheral regions to form depletion layers similar to the active region, maintaining high breakdown voltage throughout the device.
Solution Approach 2:
The alternating conductivity type structure serves dual functions: in the active section, it reduces the tradeoff between on-resistance and breakdown voltage; in the peripheral section, it provides the necessary breakdown voltage protection. This multi-functionality eliminates the need for separate peripheral structures.
4Reliability
If the pitch of alternating conductivity type layers in peripheral section is narrowed to relax surface electric field, then breakdown voltage is maintained, but device complexity increases
Solution Approach 1:
The peripheral section uses the same alternating conductivity type segmentation as the active section, creating a consistent pattern throughout. This segmentation naturally relaxes the surface electric field through the pn-junction depletion layers without requiring additional complex structures.
Solution Approach 2:
The alternating conductivity type structure performs the dual role of reducing on-resistance/breakdown voltage tradeoff in the active region and providing breakdown voltage protection in the peripheral region. This universal application simplifies the overall device structure by eliminating the need for separate peripheral protection structures.
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 the avalanche withstanding capability, allowing for higher current flow and secure breakdown voltage, even with variations in impurity concentrations, by raising the avalanche voltage and relaxing negative resistance characteristics in the peripheral section.
Implementation Method 1
the depletion layers expand laterally from the pn-junctions extending vertically, to the direction of the alternate arrangement of the constituent regions, depleting the entire drift layer
Implementation Method 2
The proposed structure relaxes the surface electric field near the active section of device to maintain a high breakdown voltage
Implementation Method 3
For improving the avalanche withstanding capability of the drift layer in the superjunction semiconductor device, a structure that improves the negative resistance formed during the avalanche breakdown has been proposed
Data Source
AI summary
The superjunction semiconductor device includes a drain drift section, which includes a first alternating conductivity type layer formed of first n-type regions and first p-type regions arranged alternately. The device also includes a peripheral section around the drain drift section, which includes a second alternating conductivity type layer formed of second n-type regions and second p-type regions arranged alternately. The peripheral section further includes a third alternating conductivity type layer in its surface portion. The third alternating conductivity type layer is formed of third n-type regions and third p-type regions arranged alternately. At least the peripheral section is configured to improve the avalanche withstanding capability over the entire device.