SiC Epitaxial Substrate Flatness Under High-Temperature Processing
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Solution Overview
Problem
Silicon carbide semiconductor substrates with large diameters exhibit low flatness during high-temperature heat treatment, leading to difficulties in processing and increased defects such as cracking and variations in impurity regions, which hinder efficient production of semiconductor devices.
Innovation Solution
A manufacturing method involving chemical mechanical polishing (CMP) of the backside surface of a silicon carbide substrate to remove damaged layers, ensuring a high degree of flatness even at elevated temperatures, allowing for precise ion implantation and reduced defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If silicon carbide crystals are cultivated using conventional methods, then production cost is reduced, but crystal quality deteriorates due to high dislocation density
Solution Approach 1:
The patent changes the physical-chemical parameters of the crystal cultivation process by introducing a silicon oxide layer and controlling oxygen partial pressure during sublimation, transforming conventional low-cost methods into a high-quality production process that reduces dislocation density while maintaining economic feasibility
Solution Approach 2:
A silicon oxide layer is introduced as an intermediary substance between the silicon carbide crystal and the cultivation environment. This intermediate layer controls oxygen diffusion and protects the crystal during growth, enabling high-quality crystal formation without requiring expensive conventional techniques
2Manufacturing precision
If conventional crystal cultivation methods are used, then production cost is low, but metal contamination increases
Solution Approach 1:
The patent creates an inert atmosphere by controlling oxygen partial pressure and introducing a silicon oxide barrier layer, which prevents metal contamination from the cultivation environment while maintaining a cost-effective process compared to ultra-high vacuum or purified atmosphere methods
3Manufacturing precision
If conventional methods are used to cultivate silicon carbide crystals, then production is economical, but crystal defects increase
Solution Approach 1:
The silicon oxide layer is formed in advance before crystal cultivation, and oxygen partial pressure is pre-controlled during the sublimation process. This preliminary preparation prevents defect formation during crystal growth, achieving low defect density without requiring complex real-time intervention systems
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 produces silicon carbide semiconductor substrates with a high degree of flatness and reduced warpage, enabling efficient and high-yield production of semiconductor devices by minimizing cracking and variations in impurity regions.
Implementation Method 1
it has been found that a silicon oxide layer formed on a silicon carbide crystal suppresses diffusion of oxygen into the crystal
Implementation Method 2
By controlling the partial pressure of oxygen gas during sublimation, formation of graphite and silicon oxide on the crystal surface can be prevented
Implementation Method 3
During cultivation of silicon carbide crystals by sublimation
Data Source
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AI summary
A silicon carbide semiconductor substrate (10) includes: a base substrate (1) that has a main surface having an outer diameter of not less than 100 mm and that is made of single-crystal silicon carbide; and an epitaxial layer (2) formed on the main surface (1A). The silicon carbide semiconductor substrate (10) has an amount of warpage of not less than -100 µm and not more than 100 µm when a substrate temperature is a room temperature and has an amount of warpage of not less than -1.5 mm and not more than 1.5 mm when the substrate temperature is 400°C.