Nitride Semiconductor Substrate Stress Mapping for Crack Suppression
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Solution Overview
Problem
Existing Group-III element nitride semiconductor substrates face challenges in suppressing cracks and fractures due to residual stress, which cannot be adequately evaluated by surface evaluation methods like Raman analysis and cathode luminescence, leading to insufficient control over stress distribution across the substrate.
Innovation Solution
A Group-III element nitride semiconductor substrate with a thickness of 200 μm or more, characterized by a high number of light-and-dark switching events in crossed-Nicols images observed under a polarizing microscope, indicating reduced stress fluctuations, and a bonded substrate configuration to enhance structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If surface evaluation methods like Raman analysis and cathode luminescence are used, then surface stress can be evaluated, but internal stress and stress distribution throughout the substrate cannot be adequately assessed
Solution Approach 1:
The patent transitions from surface-only evaluation (2D) to three-dimensional evaluation by observing the substrate from both front and back surfaces. This dimensional expansion enables assessment of internal stress distribution throughout the substrate thickness, not just at the surface level.
Solution Approach 2:
The patent introduces a new evaluation methodology using polarized light observation as an intermediary technique. This method serves as a bridge between surface evaluation and internal stress assessment, enabling visualization of stress distribution throughout the substrate volume through optical interference patterns.
2Strength
If substrate thickness is increased to suppress cracks and fractures, then structural integrity improves, but device manufacturing complexity and processing difficulty increase
Solution Approach 1:
The patent applies preliminary stress relief measures during substrate fabrication, including controlled cooling processes and annealing treatments. These preliminary actions prevent stress accumulation that would otherwise require complex post-processing steps to address.
Solution Approach 2:
The patent optimizes substrate thickness as a critical parameter, establishing specific thickness ranges that balance mechanical strength with processability. By carefully controlling thickness parameters during fabrication, the patent achieves adequate structural integrity without excessive processing complexity.
3Reliability
If residual stress in the substrate is reduced, then crack and fracture occurrence decreases, but manufacturing precision and stress control requirements become more stringent
Solution Approach 1:
The patent implements a feedback mechanism through dual-surface observation using polarized light. By monitoring stress distribution patterns on both front and back surfaces, manufacturers can adjust processing parameters in real-time to maintain stress within acceptable ranges, ensuring reliable crack suppression.
Solution Approach 2:
The patent applies preliminary stress control measures during fabrication, including controlled cooling rates and annealing processes. These preliminary actions prevent excessive stress accumulation before it becomes a problem, reducing the need for corrective measures and simplifying manufacturing precision requirements.
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 approach effectively suppresses cracks and fractures by visualizing and managing stress distribution throughout the substrate, providing a freestanding substrate suitable for various semiconductor devices with improved reliability and reduced device variability.
Implementation Method 1
the number N of times of light-and-dark switching in a line segment having a length of 2 mm, which is drawn in a crossed-Nicols image obtained by observation of a region including a central portion of a surface of the first surface with a polarizing microscope
Data Source
AI summary
A Group-III element nitride semiconductor substrate includes: a first surface; and a second surface. The Group-III element nitride semiconductor substrate has a thickness of 200 μm or more. In one embodiment, the number N of times of light-and-dark switching in a line segment having a length of 2 mm, which is drawn in a crossed-Nicols image obtained by observation of a region including a central portion of a surface of the first surface with a polarizing microscope, is 50 or more.