Semiconductor Device Withstand Capability Reverse Recovery
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Solution Overview
Problem
Conventional semiconductor devices face challenges in improving withstand capability during reverse recovery, as they struggle to simultaneously reduce carrier injection during forward bias and differentiate the location of electric field focus from the current focus during reverse recovery, leading to easy breakdown.
Innovation Solution
A semiconductor device structure is implemented with a semiconductor substrate having distinct regions of varying impurity concentrations, where a p-type second region and a higher concentration p-type third region are formed adjacent to an n-type first region, with an insulating film covering the third region, allowing for reduced carrier injection and separating the electric field and current focus locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the anode region is covered with an insulating film to isolate end portions, then the withstand capability during reverse recovery is improved, but the device complexity increases due to additional manufacturing steps
Solution Approach 1:
The patent applies local quality by creating regions with different impurity concentrations (first region with 3.5×10^16 to 4.5×10^16 cm^-3, second region with 1.0×10^17 to 2.0×10^17 cm^-3, third region with 3.5×10^18 to 4.5×10^18 cm^-3) at specific locations. The high-concentration second and third regions are positioned where electric field concentration occurs during reverse recovery, providing localized field control without requiring complete insulating film coverage, thus improving reliability while reducing manufacturing complexity.
2Reliability
If the impurity concentration in the anode region is increased to reduce carrier injection, then the reverse recovery performance improves, but the forward voltage drop increases
Solution Approach 1:
The patent implements local quality by concentrating high impurity concentrations (second region: 1.0×10^17 to 2.0×10^17 cm^-3, third region: 3.5×10^18 to 4.5×10^18 cm^-3) only in specific areas where electric field concentration occurs during reverse recovery, rather than uniformly throughout the entire anode region. This localized approach reduces carrier injection at critical points while maintaining lower overall impurity concentration, thereby improving reverse recovery performance without significantly increasing forward voltage drop.
Solution Approach 2:
The anode region is segmented into multiple regions with different impurity concentrations: the first region (3.5×10^16 to 4.5×10^16 cm^-3), second region (1.0×10^17 to 2.0×10^17 cm^-3), and third region (3.5×10^18 to 4.5×10^18 cm^-3). This segmentation allows each region to serve different functions - the lower concentration first region maintains good forward conduction, while the higher concentration second and third regions control reverse recovery behavior, thus resolving the contradiction between forward voltage drop and reverse recovery performance.
Data Source
AI summary
To improve withstand capability of a semiconductor device during reverse recovery, provided is a semiconductor device including a semiconductor substrate having a first conduction type; a first region having a second conduction type that is formed in a front surface of the semiconductor substrate; a second region having a second conduction type that is formed adjacent to the first region in the front surface of the semiconductor substrate and has a higher concentration than the first region; a third region having a second conduction type that is formed adjacent to the second region in the front surface of the semiconductor substrate and has a higher concentration than the second region; an insulating film that covers a portion of the second region and the third region; and an electrode connected to the second region and the first region that are not covered by the insulating film.