Field Stop Doping Profile for Soft-Switching Semiconductor Reliability
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Solution Overview
Problem
Semiconductor devices face challenges in achieving sufficient softness during switching without increasing chip thickness, which affects breakdown voltage and cosmic ray failure rates due to the tradeoffs in device geometry and field stop region design.
Innovation Solution
Incorporating a field stop region with a first and second sub-region, where hydrogen-related donors have a specific concentration gradient, increasing from a pn-junction to a maximum value and then decreasing to a reference value, with a controlled vertical gradient to optimize doping profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the chip thickness is reduced to improve dynamic characteristics and reduce static losses, then the breakdown voltage decreases and cosmic ray failure rate increases
Solution Approach 1:
The field stop region is divided into two sub-regions with different hydrogen-related donor concentration profiles. The first sub-region has a steadily increasing concentration from the pn-junction to a maximum value, while the second sub-region has a steadily decreasing concentration from the maximum value to a reference value at the drift region interface. This segmentation allows optimized control of charge carrier plasma and electric field distribution, enabling thin chip design with maintained reliability.
Solution Approach 2:
Different regions of the field stop structure are assigned different hydrogen-related donor concentration characteristics. The first sub-region provides strong plasma protection near the pn-junction, while the second sub-region provides controlled field distribution toward the drift region. This local differentiation enables the thin chip to achieve both soft switching and adequate breakdown voltage.
2Ease of operation
If a deep field stop region is introduced to improve softness during switching, then the maximum electric field increases but breakdown voltage decreases and cosmic ray FIT rate increases
Solution Approach 1:
The hydrogen-related donor concentration is precisely controlled with specific gradient requirements: steadily increasing in the first sub-region, steadily decreasing in the second sub-region, with the maximum concentration in the second sub-region being at most 20% larger than the reference value. This parameter optimization enables soft switching characteristics while maintaining adequate breakdown voltage and reducing cosmic ray sensitivity.
3Productivity
If device geometries are shrunk to reduce costs and increase device functionalities per unit area, then costs decrease but tradeoffs and challenges increase in meeting device functionalities
Solution Approach 1:
By optimizing the hydrogen-related donor concentration parameters (steady increase then steady decrease profiles, maximum concentration limits, gradient ratios), the patent enables advanced device functionalities in shrunk geometries while managing the complexity through well-defined concentration constraints that balance multiple performance requirements.
Data Source
AI summary
A semiconductor device includes: a drift region of a first conductivity type between first and second surfaces of a semiconductor body; a first region of a second conductivity type at the second surface; and a field stop region of the first conductivity type between the drift region and first region. The field stop region includes first and second sub-regions with hydrogen related donors. A p-n junction separates the first region and first sub-region. A concentration of hydrogen related donors, along a first vertical extent of the first sub-region, steadily increases from the pn-junction to a maximum value, and steadily decreases from the maximum value to a value at a first transition between the sub-regions. A second vertical extent of the second sub-region ends at a second transition to the drift region where the concentration of hydrogen related donors equals 10% of the value at the first transition.