SiC Substrate Structure to Suppress Junction Interface Defects
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Solution Overview
Problem
The existing methods for manufacturing semiconductor substrates using SiC face challenges such as high manufacturing costs, low throughput, and defects at the junction interface due to the need for high-quality single crystal substrates, which are costly to produce and require complex processing. Additionally, polycrystal substrates often have surface concavities that reduce device reliability and withstand voltage.
Innovation Solution
A semiconductor substrate structure comprising a single crystal SiC layer and a polycrystal SiC layer, where the polycrystal layer is grown on the single crystal layer using CVD, eliminating the need for a junction interface and reducing defects. This structure includes a drift layer, a buffer layer, and a substrate layer, all connected without an interface, allowing for high-speed CVD growth and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single crystal SiC substrate is bonded to a polycrystal SiC substrate to reduce manufacturing costs, then manufacturing cost is reduced, but defects occur at the junction interface
Solution Approach 1:
The patent merges the single crystal SiC layer and polycrystal SiC substrate into a unified structure where the single crystal layer is grown directly on the polycrystal substrate via CVD. This eliminates the need for separate bonding processes and the associated junction interface defects, while maintaining cost benefits by using polycrystal substrate as the base.
Solution Approach 2:
The patent introduces a buffer layer as an intermediary between the single crystal SiC layer and the polycrystal SiC substrate. This buffer layer mediates the transition between the two different crystal structures, reducing defects at the interface and improving overall device reliability while maintaining the cost advantages of using polycrystal substrate.
2Manufacturing precision
If high-quality single crystal substrates are used to ensure crystal quality, then epitaxial growth quality is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies local quality by ensuring high crystal quality only in the specific region where epitaxial growth occurs (the single crystal SiC layer), while the underlying substrate can be polycrystal with lower cost. This localized approach to quality control maintains the necessary crystal quality for device performance without requiring the entire substrate to be expensive single crystal material.
Solution Approach 2:
The patent segments the substrate structure into two distinct parts: a polycrystal SiC substrate for mechanical support and cost efficiency, and a single crystal SiC layer for high-quality epitaxial growth. This segmentation allows each part to fulfill its specific function optimally while balancing cost and quality requirements.
3Manufacturing precision
If polishing processes are applied to ensure surface roughness for bonding, then bonding quality is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the complex polishing process from the manufacturing sequence by using CVD growth to directly form the single crystal SiC layer on the polycrystal substrate. The CVD process inherently produces a smooth, high-quality surface without requiring separate polishing steps, thereby reducing manufacturing complexity while maintaining surface quality.
4Ease of manufacture
If remote epitaxy with graphene film is used to grow SiC epitaxial layer, then epitaxial growth is facilitated, but process complexity increases
Solution Approach 1:
The patent replaces the complex remote epitaxy process with graphene film with a simpler direct CVD growth method. The direct CVD approach uses readily available precursors and standard equipment to grow the single crystal SiC layer directly on the polycrystal substrate, eliminating the need for graphene film deposition and the associated process complexity.
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 approach reduces manufacturing costs, enhances throughput, and improves the reliability of semiconductor devices by eliminating junction interface defects and the need for costly polishing processes, while maintaining desired physical properties and mechanical strength.
Implementation Method 1
a second layer that is formed on the first layer and is formed of a SiC semiconductor which includes a polycrystalline structure, in which the second layer is a formed on the surface of the first layer by means of CVD growth
Data Source
AI summary
A semiconductor substrate includes a drift layer of a first layer formed of a single crystal SiC semiconductor and a buffer layer and a substrate layer of a second layer that is formed of a SiC semiconductor which includes a polycrystalline structure and is formed on the surface of the first layer, in which the second layer (12) is formed on the surface of the drift layer of the first layer by means of CVD growth, the drift layer of the first layer is formed by means of epitaxial growth, and accordingly, defects occurring at a junction interface of the semiconductor substrate including the single crystal SiC layer and the polycrystal SiC layer are suppressed, and manufacturing costs are also reduced.