Semiconductor Substrate Trench Crystallinity Recovery
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Solution Overview
Problem
Existing manufacturing methods for semiconductor substrates with high aspect ratio trenches for PN columns in super junction structures fail to completely prevent crystal defects, leading to leak current issues due to insufficient removal of damage layers during the etching process.
Innovation Solution
A method involving dry etching to form trenches, followed by chemical etching to remove a first damage layer exceeding 50 nanometers and high-temperature heat treatment in non-oxidizing gas to recover the crystallinity of a second damage layer, ensuring the epitaxial film grown in the trench has high crystallinity and minimizes leak current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a trench with high aspect ratio is formed to create PN columns in super junction structure, then the device achieves high breakdown voltage capability, but crystal defects increase due to anisotropic etching process
Solution Approach 1:
The patent applies preliminary action by performing a first heat treatment at 900-1100°C for a few minutes to tens of minutes before epitaxial growth to smooth the rough inner wall of the trench and recover crystallinity. This preliminary recovery of crystal structure prevents subsequent crystal defects during epitaxial film formation, thereby maintaining high breakdown voltage capability while eliminating the reliability issue caused by etching-induced crystal defects
Solution Approach 2:
The patent changes the temperature parameter by performing heat treatment at elevated temperatures (900-1100°C) to recover crystallinity in the trench inner wall. This parameter change transforms the damaged crystal structure caused by anisotropic etching into a recovered structure with proper crystallinity, preventing leak current and ensuring high breakdown voltage performance
2Productivity
If heat treatment is performed at lower temperature for shorter time, then process efficiency is improved, but crystallinity recovery is insufficient leading to leak current
Solution Approach 1:
The patent optimizes the temperature parameter by setting the heat treatment temperature to 1050°C or higher, which is sufficient to recover crystallinity and prevent leak current while maintaining reasonable process time. This parameter optimization balances productivity and reliability by achieving complete crystallinity recovery without excessive processing time
Solution Approach 2:
The patent replaces prolonged low-temperature treatment with high-temperature short-duration treatment, substituting a time-intensive process with a thermally intensive process that achieves the same crystallinity recovery goal more efficiently, thereby improving productivity while ensuring reliability
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 method effectively restricts leak current generation, enabling complete depletion of PN columns and achieving high breakdown voltage in semiconductor devices.
Implementation Method 1
etching a surface portion of an inner wall of the trench by a chemical etching method so that a first damage layer is removed
Implementation Method 2
performing a heat treatment at temperature equal to or higher than 1050° C. in non-oxidizing and non-azotizing gas so that crystallinity of a second damage layer is recovered
Implementation Method 3
performing a heat treatment at temperature equal to or higher than 1050° C. in non-oxidizing and non-azotizing gas so that crystallinity of a second damage layer is recovered
Data Source
AI summary
A manufacturing method of a semiconductor substrate includes: forming a trench in a semiconductor board by a dry etching method; etching a surface portion of an inner wall of the trench by a chemical etching method so that a first damage layer is removed, wherein the surface portion has a thickness equal to or larger than 50 nanometers; and performing a heat treatment at temperature equal to or higher than 1050° C. in non-oxidizing and non-azotizing gas so that crystallinity of a second damage layer is recovered, wherein the second damage layer is disposed under the first damage layer. The crystallinity around the trench is sufficiently recovered.