Superjunction Gradient Doping Epitaxy for Void-Free Trench Filling
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Solution Overview
Problem
Super-junction MOSFETs with smaller vertical pn junctions face challenges in filling trenches without voids while maintaining charge balance, leading to electromagnetic interference and degradation in breakdown voltage.
Innovation Solution
A method involving epitaxial growth to deposit an n-doped silicon layer with increasing dopant concentration from bottom to top, followed by etching to form tapered trenches, and filling these trenches with p-doped material to form pillars, which helps in reducing void formation and achieving charge balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the size of multiple vertical pn junctions is reduced, then the ON-resistance is reduced, but filling the trenches without voids becomes difficult
Solution Approach 1:
The patent applies parameter changes by implementing a gradient doping profile in the n-doped layer, where the dopant concentration varies continuously from the bottom to the top of the layer. This gradual change in doping parameters enables better control of the epitaxial growth process, allowing complete trench filling without voids while maintaining the reduced junction size needed for low ON-resistance.
Solution Approach 2:
The patent employs preliminary action by pre-forming the n-doped layer with a specific gradient doping profile before the trench etching and p-doped material deposition steps. This preparatory doping structure creates optimal conditions for subsequent trench filling, ensuring that the trenches can be completely filled without voids from the outset.
2Strength
If the size of multiple vertical pn junctions is reduced, then the ON-resistance is reduced, but maintaining charge balance between p and n regions becomes difficult
Solution Approach 1:
The patent resolves the charge balance issue through parameter changes by implementing a gradient doping profile where the dopant concentration in the n-doped layer varies from bottom to top. This continuous parameter variation compensates for the reduced junction size, maintaining the necessary charge balance between p and n regions while preserving the low ON-resistance characteristic.
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 approach effectively reduces void formation and improves charge balance between n-doped and p-doped regions, enhancing breakdown voltage and preventing electromagnetic interference.
Implementation Method 1
depositing, via a first epitaxial growth process, an n-doped silicon material onto a substrate to form an n-doped layer
Implementation Method 2
depositing, via a first epitaxial growth process, an n-doped silicon material onto a substrate
Implementation Method 3
etching the n-doped layer to form a plurality of trenches having sidewalls that are tapered
Data Source
AI summary
Embodiments of processing a substrate are provided herein. In some embodiments, a method of processing a substrate includes: depositing, via a first epitaxial growth process, an n-doped silicon material onto a substrate to form an n-doped layer while adjusting a ratio of dopant precursor to silicon precursor so that a dopant concentration of the n-doped layer increases from a bottom of the n-doped layer to a top of the n-doped layer; etching the n-doped layer to form a plurality of trenches having sidewalls that are tapered and a plurality of n-doped pillars therebetween; and filling the plurality of trenches with a p-doped material via a second epitaxial growth process to form a plurality of p-doped pillars.