Epitaxial Drift Layer Dopant Profile for Soft Switching
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Solution Overview
Problem
Existing semiconductor devices face challenges in achieving soft switch-off behavior and minimizing switching losses, particularly in high-frequency hard-switching applications, where early or sudden reverse recovery current breakdown is a concern.
Innovation Solution
The method involves epitaxial growth of semiconductor layers, including a back side emitter layer and a drift layer with specific dopant concentration profiles, creating a pn-junction and a buffer layer with varying dopant concentrations to optimize switching behavior and reduce electric field stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional drift layer with uniform dopant concentration is used, then the manufacturing process is simple, but the switching behavior is hard and switching losses are high
Solution Approach 1:
The drift layer is designed with non-uniform dopant concentration, where the dopant concentration varies along the vertical direction. Specifically, the dopant concentration is higher near the back side emitter layer and decreases toward the front side, creating local variations in electrical properties that enable soft switching behavior while maintaining low switching losses
Solution Approach 2:
The dopant concentration parameter in the drift layer is changed from a uniform value to a graded profile. This parameter variation along the vertical direction modifies the electric field distribution and carrier transport characteristics, achieving improved switching behavior without excessive complexity in the manufacturing process
2Reliability
If the dopant concentration in the drift layer is increased to improve voltage blocking, then the voltage blocking capability is enhanced, but the switching losses increase
Solution Approach 1:
Different regions of the drift layer have different dopant concentrations optimized for their specific functions: the region near the back side emitter layer has higher dopant concentration for voltage blocking, while the region near the front side has lower dopant concentration for reduced switching losses and improved carrier extraction
Solution Approach 2:
The dopant concentration is varied along the vertical dimension of the drift layer, creating a graded profile that simultaneously satisfies both voltage blocking and switching performance requirements by distributing dopants non-uniformly in the vertical direction
3Reliability
If a buffer layer is added between the back side emitter layer and drift layer, then the electric field stress is reduced and device ruggedness is improved, but the manufacturing process becomes more complex
Solution Approach 1:
A buffer layer is introduced as an intermediate layer between the back side emitter layer and the drift layer. This buffer layer has intermediate dopant concentration that acts as a transition region, reducing electric field stress at the junction and improving device ruggedness while integrating smoothly with the existing layer structure
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 approach enables a semiconductor device with improved soft switching behavior, reduced switching losses, and enhanced ruggedness, while maintaining high voltage blocking capabilities.
Implementation Method 1
epitaxially growing, along a vertical direction perpendicular to the surface, a back side emitter layer on top of the surface
Implementation Method 2
creating, within the drift layer, a dopant concentration profile of dopants of the first conductivity type along the vertical direction, the dopant concentration profile in the drift layer exhibiting a variation of a concentration of dopants of the first conductivity type along the vertical direction
Implementation Method 3
creating, either within or on top of the drift layer, a body region having dopants of the second conductivity type, a transition between the body region and the drift layer forming a pn-junction
Data Source
AI summary
A method of producing a semiconductor device is presented. The method comprises: providing a semiconductor substrate having a surface; epitaxially growing, along a vertical direction (Z) perpendicular to the surface, a back side emitter layer on top of the surface, wherein the back side emitter layer has dopants of a first conductivity type or dopants of a second conductivity type complementary to the first conductivity type; epitaxially growing, along the vertical direction (Z), a drift layer having dopants of the first conductivity type above the back side emitter layer, wherein a dopant concentration of the back side emitter layer is higher than a dopant concentration of the drift layer; and creating, either within or on top of the drift layer, a body region having dopants of the second conductivity type, a transition between the body region and the drift layer forming a pn-junction (Zpn). Epitaxially growing the drift layer includes creating, within the drift layer, a dopant concentration profile (P) of dopants of the first conductivity type along the vertical direction (Z), the dopant concentration profile (P) in the drift layer exhibiting a variation of a concentration of dopants of the first conductivity type along the vertical direction (Z).