Indium Phosphide Substrate Crack Reduction via Dopant Control
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Solution Overview
Problem
Indium phosphide crystal substrates produced by the vertical gradient freeze method suffer from high defect ratios due to cracking in flat and notch portions, which complicates substrate manufacturing and epitaxial layer growth.
Innovation Solution
The indium phosphide crystal substrate is designed with specific dimensions and dopant concentrations, including sulfur, tin, and iron, to maintain average dislocation densities and residual strains within prescribed ranges in flat and notch regions, thereby reducing crack defect ratios during substrate manufacturing and epitaxial layer growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the vertical gradient freeze method is used to grow indium phosphide crystal substrates, then large diameter substrates (100-205 mm) can be produced, but high defect ratios due to cracking occur in flat and notch portions
Solution Approach 1:
The patent applies parameter changes by precisely controlling dopant concentrations (sulfur: 2.0×10^18 to 8.0×10^18 cm^-3, tin: 1.0×10^18 to 4.0×10^18 cm^-3, iron: 5.0×10^15 to 1.0×10^17 cm^-3) and dimensional parameters (flat portion width: 1-5 mm, notch portion dimensions) to reduce crack defect ratios while maintaining large substrate diameter production
2Ease of operation
If flat portions and notch portions are added to the substrate outer edge for orientation and handling, then ease of operation is improved, but manufacturing complexity and defect ratios increase
Solution Approach 1:
The patent applies local quality by creating specific structural features (flat portions and notch portions) at localized areas of the substrate outer edge while maintaining uniform dopant distribution in the bulk material. The flat portion has a width of 1-5 mm and the notch portion has specific dimensional parameters, providing localized functionality for orientation and handling without compromising overall substrate integrity
3Manufacturing precision
If dopant concentrations are increased to control dislocation density, then manufacturing precision is improved, but the risk of cracking in flat and notch portions increases
Solution Approach 1:
The patent resolves this contradiction through parameter changes by establishing optimal dopant concentration ranges (sulfur: 2.0×10^18 to 8.0×10^18 cm^-3, tin: 1.0×10^18 to 4.0×10^18 cm^-3, iron: 5.0×10^15 to 1.0×10^17 cm^-3) that simultaneously achieve low dislocation densities (10-500 cm^-2 in flat region, 500-5000 cm^-2 in notch region) and reduced crack defect ratios, rather than using excessively high dopant concentrations
Data Source
AI summary
An indium phosphide crystal substrate has a diameter of 100-205 mm and a thickness of 300-800 μm and includes any of a flat portion and a notch portion. In any of a first flat region and a first notch region, when an atomic concentration of sulfur is from 2.0×1018 to 8.0×1018 cm−3, the indium phosphide crystal substrate has an average dislocation density of 10-500 cm−2, and when am atomic concentration of tin is from 1.0×1018 to 4.0×1018 cm−3 or an atomic concentration of iron is from 5.0×1015 to 1.0×1017 cm−3, the indium phosphide crystal substrate has an average dislocation density of 500-5000 cm−2.