Selective Isotropic Growth for Crack-Free Nitride Semiconductor Substrates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The growth of high-quality nitride semiconductors on silicon substrates often results in stress-induced cracks due to lattice and thermal expansion coefficient differences, hindering the commercialization of optical and electronic devices.
Innovation Solution
A method involving the formation of stop patterns and transition layers around the substrate edges, using selective isotropic growth to prevent crack formation by ensuring the epitaxial semiconductor layer grows from the transition layer surfaces and sidewalls, not the stop patterns, thereby isolating potential cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high-quality nitride semiconductor is grown on silicon substrate, then manufacturing cost is reduced and mass production is enabled, but stress-induced cracks occur due to lattice constant and thermal expansion coefficient differences
Solution Approach 1:
The patent applies preliminary action by forming a buffer layer and transition layer on the silicon substrate before growing the GaN epitaxial layer. These preliminary layers are designed to gradually transition the lattice structure and reduce thermal stress, preventing crack formation before the main semiconductor layer is grown. The buffer layer with specific thickness and composition is prepared in advance to accommodate the lattice mismatch between silicon and GaN.
Solution Approach 2:
The patent uses intermediary layers (buffer layer and transition layer) that mediate between the silicon substrate and the GaN epitaxial layer. These intermediary layers have graded compositions and structures that gradually bridge the lattice constant difference and thermal expansion coefficient difference, acting as a stress-absorbing interface that prevents direct stress transmission and crack formation.
2Area of stationary object
If epitaxial semiconductor layer is grown from stop pattern, then growth coverage is improved, but crack formation is induced at the edge of the semiconductor substrate
Solution Approach 1:
The patent applies local quality by creating different growth conditions in different regions of the substrate. The stop pattern is designed with specific local properties (material composition, thickness, geometry) that prevent epitaxial growth at the edges while allowing normal growth in the center region. This localized control of growth characteristics prevents edge crack formation while maintaining adequate coverage of the active device areas.
Solution Approach 2:
The patent segments the substrate surface into different functional zones using the stop pattern. The stop pattern creates distinct regions where epitaxial growth is suppressed at the edges and permitted in the center. This segmentation allows independent optimization of edge regions (crack prevention) and center regions (device fabrication), resolving the contradiction between coverage and crack resistance.
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 effectively prevents crack formation in the epitaxial semiconductor layer, enhancing the reliability and manufacturability of semiconductor substrates for applications like LEDs and wireless communication devices.
Implementation Method 1
The epitaxial semiconductor layer may be isotropically grown from a top surface and a sidewall of the transition layer by a selective isotropic growth method, so that the epitaxial semiconductor layer may gradually cover the stop pattern
Implementation Method 2
the transition layer may be formed by a selective anisotropic growth method, so that the transition layer may not be grown from the stop pattern but may be grown from an exposed top surface of the substrate
Implementation Method 3
The silicon oxide may be formed by a selective thermal oxidation process
Data Source
AI summary
The inventive concept provides methods for manufacturing a semiconductor substrate. The method may include forming a stop pattern surrounding an edge of a substrate, forming a transition layer an entire top surface of the substrate except the stop pattern, and forming an epitaxial semiconductor layer on the transition layer and the stop pattern. The epitaxial semiconductor layer may not be grown from the stop pattern. That is, the epitaxial semiconductor layer may be isotropically grown from a top surface and a sidewall of the transition layer by a selective isotropic growth method, so that the epitaxial semiconductor layer may gradually cover the stop pattern.