IGBT Epitaxy via Oxide Passivation for Defect Reduction
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Solution Overview
Problem
The existing low voltage IGBT epitaxy technology faces challenges with consistency in thickness and specific resistance due to surface defects in the substrate material, leading to poor epitaxial layer quality and performance issues, especially as substrate size increases.
Innovation Solution
A method for manufacturing IGBTs that involves forming a field stop layer, growing an oxide layer, and then removing it to reduce surface defects, followed by epitaxial growth, using techniques like dry-oxygen oxidation and wet etching to improve substrate quality and epitaxial layer consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low voltage epitaxy technology is used to eliminate auto-dope of N-type impurities, then the auto-dope effect is reduced, but the temperature gradient increases causing stacking faults and dislocations
Solution Approach 1:
The patent changes the voltage parameter during the epitaxy process. It uses high voltage (900-1100V) for the initial epitaxy growth to reduce temperature gradient and defects, then switches to low voltage (600-700V) for subsequent growth to eliminate auto-dope effects. This dynamic parameter change resolves the contradiction between temperature gradient control and impurity doping control.
2Ease of manufacture
If injection is performed before epitaxy on P-type substrate, then the field stop layer is formed, but surface defects increase leading to poor epitaxial layer quality
Solution Approach 1:
The patent performs preliminary oxidation to grow an oxide layer on the substrate surface before epitaxy. This preliminary action passivates surface defects and provides a cleaner interface for epitaxial growth, reducing defect propagation from the substrate to the epitaxial layer while maintaining the field stop layer structure.
Solution Approach 2:
The oxide layer acts as an intermediary between the substrate with field stop layer and the epitaxial layer. It provides a fresh, defect-free surface for epitaxy to grow on, mediating the interaction between the defective substrate surface and the quality requirements of the epitaxial layer.
3Productivity
If substrate diameter is increased for larger production, then productivity improves, but surface defects increase causing greater parameter deterioration
Solution Approach 1:
The preliminary oxidation step is particularly important for large diameter substrates as it uniformly passivates the entire surface, including edge regions that are more prone to defects. This creates a consistent starting surface across the whole large substrate, enabling uniform epitaxial growth and maintaining parameter consistency despite the increased substrate size.
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 method effectively reduces surface defects and improves the quality of the epitaxial layer, enhancing the overall performance and consistency of the IGBTs, particularly for larger substrates.
Implementation Method 1
growing an oxide layer on the field stop layer
Implementation Method 2
removing the oxide layer on the field stop layer
Implementation Method 3
forming an epitaxial layer on the filed stop layer when the oxide layer is removed
Data Source
AI summary
An insulated gate bipolar transistor (IGBT) manufacturing method comprises the following steps: providing a semiconductor substrate of a first conducting type, the semiconductor substrate having a first major surface and a second major surface (100); forming a field-stop layer of a second conducting type on the first major surface of the semiconductor substrate (200); growing an oxide layer on the field-stop layer (300); removing the oxide layer from the field-stop layer (400); forming an epitaxial layer on the field-stop layer from which the oxide layer has been removed; and then manufacturing an IGBT on the epitaxial layer (600). Before regular manufacturing of an IGBT, the surface defects of a substrate material are eliminated as many as possible before epitaxy is formed, and the quality of an epitaxial layer is improved, thereby improving the quality of the whole IGBT.