Composite SiC Substrate With Atomic Steps for Thick Epitaxy
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Solution Overview
Problem
Existing silicon carbide substrates fail to meet the stringent requirements for high-voltage power devices, particularly in terms of surface quality and thickness of the epitaxial layer, leading to defects and reduced reliability of semiconductor devices.
Innovation Solution
A composite silicon carbide substrate is developed, comprising a single crystal layer, a bonding layer, and a support layer, with a periodic atomic step structure on the surface of the single crystal layer. This structure facilitates step-flow growth of the epitaxial layer, minimizing defects such as polytype phase transformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the epitaxial layer is increased to meet high-voltage device requirements, then the voltage resistance and power handling capability are improved, but the requirements on substrate surface quality become more stringent, leading to increased manufacturing difficulty
Solution Approach 1:
The patent changes the surface morphology parameters of the substrate by introducing atomic step structures with specific step heights (1-10 nm) and step densities (10^6-10^8 steps/cm). These parameter changes enable the substrate to support thicker epitaxial layers while maintaining uniform growth and avoiding defects, thus resolving the contradiction between increased epitaxial thickness for voltage resistance and substrate surface quality requirements.
Solution Approach 2:
The patent applies local quality by creating specific atomic step structures at the substrate surface rather than requiring uniform high-quality polishing across the entire surface. The atomic steps are concentrated in specific regions and configurations that locally guide epitaxial growth, allowing thicker epitaxial layers to be grown uniformly without requiring the entire substrate surface to meet extremely stringent flatness specifications.
2Manufacturing precision
If conventional polishing methods are used to achieve low surface roughness, then the surface roughness is reduced, but subsurface damage and scratches are introduced, affecting epitaxial layer quality
Solution Approach 1:
The patent converts the harmful effect of mechanical polishing into a beneficial atomic step structure. Instead of attempting to completely eliminate subsurface damage through ultra-fine polishing, the invention uses controlled chemical etching to transform the damaged surface into a patterned atomic step structure. The atomic steps serve as growth guides that promote uniform epitaxial growth and actually reduce the impact of subsurface damage, thus converting a harmful factor into a beneficial feature.
3Manufacturing precision
If ultra-fine polishing is applied to achieve TTV less than 10 μm, then the thickness uniformity is improved, but the manufacturing complexity and time increase
Solution Approach 1:
The patent replaces the mechanical polishing system with a chemical etching system to achieve the desired surface structure. Instead of using multiple stages of mechanical polishing with progressively finer abrasives to achieve TTV < 10 μm, the invention uses chemical etchants that selectively remove material to form atomic step structures. This chemical approach achieves comparable or superior thickness uniformity with simpler process steps and reduced manufacturing time.
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 composite silicon carbide substrate enables the growth of high-quality silicon carbide epitaxial layers with large thickness, meeting the needs of high-voltage power devices by reducing defects and improving surface quality.
Implementation Method 1
grow epitaxially a layer of high-quality monocrystalline silicon carbide on a monocrystalline silicon carbide substrate
Implementation Method 2
A surface of the single crystal layer away from the bonding layer is provided with a periodic atomic step structure... This structure facilitates step-flow growth of the epitaxial layer
Data Source
AI summary
Provided are a composite silicon carbide substrate and a preparation method therefor. The composite silicon carbide substrate comprises a single crystal layer, a bonding layer and a support layer which are stacked in sequence; a surface of the single crystal layer is provided with a periodic atomic step structure; the atomic step structure comprises any one of a four-width step structure, a two-width step structure or a single-width step structure. The preparation method comprises: (1) bonding a support layer with an ion-implanted single crystal substrate, and performing a heat treatment and detaching to obtain an intermediate product of the composite silicon carbide substrate; and (2) subjecting a surface of a single crystal layer of the intermediate product of the composite silicon carbide substrate obtained in step (1) to oxidation modification and polish removal alternately, that is, forming a periodic atomic step structure on the surface of the single crystal layer, to obtain the composite silicon carbide substrate. The composite silicon carbide substrate meets the needs of high-voltage power devices for silicon carbide epitaxial layers with a large thickness and high quality, and the preparation method is simple and efficient, and has good controllability.