Silicon Carbide Epitaxial Substrate for Low TTV and LTV
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Solution Overview
Problem
Silicon carbide epitaxial substrates face exposure failure due to large total thickness variation (TTV) and local thickness variation (LTV) issues, which are exacerbated by temperature distributions in the susceptor during epitaxial growth, leading to uneven thickness and carrier concentration variations.
Innovation Solution
A silicon carbide epitaxial substrate configuration with a silicon carbide substrate and two epitaxial layers, where the carrier concentration of the substrate is higher than the epitaxial layers, and the substrate's thickness variation is controlled to maintain a maximum LTV of less than 3 μm in 10 mm square regions, using a hot wall type lateral CVD process to form the epitaxial layers with controlled thickness distributions matching the susceptor's temperature profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If epitaxial layers are grown using conventional CVD processes, then productivity is improved, but manufacturing precision deteriorates due to large TTV and LTV
Solution Approach 1:
The patent applies parameter changes by controlling the carrier concentration of the silicon carbide substrate to be higher than that of the epitaxial layers, and by optimizing CVD process parameters (temperature, pressure, gas flow) to achieve uniform thickness distribution across the substrate surface, thereby reducing TTV and LTV while maintaining productivity
Solution Approach 2:
The patent implements local quality by creating a non-uniform carrier concentration distribution where the substrate has higher carrier concentration than the epitaxial layers, and by controlling local thickness variations through susceptor temperature distribution management, ensuring each region grows at optimal conditions
2Productivity
If susceptor temperature distribution is increased to improve epitaxial growth rate, then productivity is improved, but manufacturing precision deteriorates due to uneven thickness
Solution Approach 1:
The patent applies dynamics by optimizing the susceptor temperature distribution dynamically during the epitaxial growth process, maintaining appropriate temperature gradients to ensure uniform growth rate across different regions of the substrate while achieving high overall productivity
Solution Approach 2:
The patent changes temperature parameters by controlling the susceptor temperature distribution to match the thermal profile required for uniform epitaxial growth, ensuring that regions with different thermal conditions achieve consistent thickness without sacrificing growth rate
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 configuration suppresses exposure failure by ensuring uniform thickness and carrier concentration across the substrate, reducing TTV and LTV, and maintaining a stable surface for photolithography processes.
Implementation Method 1
using a hot wall type lateral CVD process to form the epitaxial layers
Implementation Method 2
temperature distributions in the susceptor during epitaxial growth, leading to uneven thickness and carrier concentration variations
Data Source
AI summary
A silicon carbide epitaxial substrate includes a silicon carbide substrate, a first silicon carbide epitaxial layer, and a second silicon carbide epitaxial layer. The silicon carbide substrate has a first main surface and a second main surface opposite to the first main surface. The first silicon carbide epitaxial layer is in contact with a whole of the first main surface. The second silicon carbide epitaxial layer is in contact with a whole of the second main surface. A carrier concentration of the silicon carbide substrate is higher than a carrier concentration of each of the first silicon carbide epitaxial layer and the second silicon carbide epitaxial layer.