Superjunction Device Transition Region Uniformity
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Solution Overview
Problem
Existing superjunction devices face challenges in achieving uniform reverse breakdown voltage and overshoot current handling capability due to variations in trench depths and impurity concentrations, leading to inconsistent device performance.
Innovation Solution
The superjunction device design includes an N+ substrate with an N-type epitaxial layer, featuring parallel P-type pillars and annular columns separated from the substrate by a transition region, which enhances the uniformity of reverse breakdown voltage and current handling by maintaining a consistent distance between the pillars and the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If trenches are etched to form P-type and N-type semiconductor thin layers, then manufacturing cost is reduced and production cycle is shortened, but trench depth variations occur due to process conditions, leading to inconsistent reverse breakdown voltage and current handling capability
Solution Approach 1:
The patent changes the parameter of trench depth by introducing a transition region with graded impurity concentration between the P-type pillars and the N+ substrate. This parameter change compensates for trench depth variations, ensuring that devices with different trench depths achieve uniform reverse breakdown voltage and consistent current handling capability.
2Ease of manufacture
If the distance between semiconductor thin layers and substrate is reduced, then device breakdown voltage may vary according to process conditions, but manufacturing cost is reduced and production cycle is shortened
Solution Approach 1:
The patent introduces a transition region with graded impurity concentration as an intermediate structure between the P-type pillars and the N+ substrate. This parameter change in impurity concentration profile compensates for variations caused by different trench depths, ensuring reliable and uniform device performance while allowing flexible manufacturing.
3Manufacturing precision
If P-type and N-type semiconductor thin layers are formed by repeating epitaxial growth and photolithography, then layer precision is improved, but manufacturing cost increases and production cycle lengthens
Solution Approach 1:
The patent segments the formation process into two main stages: first, forming the N-type epitaxial layer with a transition region in one epitaxial growth process; second, forming P-type pillars through trench etching and filling. This segmentation avoids the need for repeated epitaxial growth and photolithography cycles, reducing production time while maintaining layer precision.
Solution Approach 2:
The transition region is formed in advance during the N-type epitaxial layer growth, before the P-type pillars are created. This preliminary action ensures that the graded impurity concentration profile is already in place to compensate for any future trench depth variations, improving both precision and productivity.
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 design improves the uniformity of reverse breakdown voltage and overshoot current handling capability, resulting in more consistent device performance and increased reliability across multiple devices.
Implementation Method 1
a P-type impurity is filled into the first trenches to form a plurality of P-type pillars
Implementation Method 2
an N-type epitaxial layer formed on the N+ substrate; a transition region exists in the N-type epitaxial layer and is adjacent to the surface of the N+ substrate
Data Source
AI summary
A superjunction device is disclosed, wherein P-type regions in an active region are not in contact with the N+ substrate, and the distance between the surface of the N+ substrate and the bottom of the P-type regions in the active region is greater than the thickness of a transition region in the N-type epitaxial layer. Methods for manufacturing the superjunction device are also disclosed. The present invention is capable of improving the uniformity of reverse breakdown voltage and overshoot current handling capability in a superjunction device.