Semiconductor Device With Graded Well Region for Electric Field Relaxation
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Solution Overview
Problem
Semiconductor devices face a decrease in withstand voltage due to electric field concentration, particularly in the well region, which affects the reverse recovery safe operation area (RRSOA) resistance.
Innovation Solution
A semiconductor device with a p-type well region having a high concentration portion and a low concentration portion, where the high concentration portion is formed on the active region side and the low concentration portion is formed on the outer region side, both with specific impurity concentration gradients and thicknesses, to demarcate the active and outer regions, and a p-type impurity region is formed on the surface layer to expand the depletion layer during recovery operations, thereby relaxing the electric field concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional well region structure is used, then the manufacturing process is simple, but electric field concentration occurs leading to decreased withstand voltage
Solution Approach 1:
The well region is divided into two distinct concentration portions: a first concentration portion with higher impurity concentration on the active region side, and a second concentration portion with lower impurity concentration on the outer region side. This local differentiation of impurity concentration optimizes the electric field distribution in different regions, suppressing concentration effects while maintaining manufacturing feasibility through a single well formation process.
2Ease of manufacture
If a single concentration well region is formed, then the manufacturing process is simple, but electric field concentration occurs in the outer region
Solution Approach 1:
The well region incorporates a second concentration portion with lower impurity concentration specifically positioned on the outer region side, addressing electric field concentration in areas where high concentration would be detrimental. This localized modification maintains manufacturing simplicity while improving field distribution.
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
The solution effectively suppresses electric field concentration and maintains a high withstand voltage by allowing a wider reverse recovery safe operation area, enhancing the device's non-destructive operation range during recovery current application.
Implementation Method 1
a second conductive type impurity region of the active region which is formed on the surface layer portion of the principal surface... expand the depletion layer during recovery operations, thereby relaxing the electric field concentration
Data Source
AI summary
A semiconductor device includes a first conductive type semiconductor layer which has a principal surface, a second conductive type well region which demarcates an active region and an outer region on the principal surface and is formed on a surface layer portion of the principal surface and includes a high concentration portion high in impurity concentration on the active region side and includes a low concentration portion lower in impurity concentration than the high concentration portion on the outer region side, and a second conductive type impurity region of the active region which is formed on a surface layer portion of the principal surface.