GaN Crystal Substrate Rear Surface Warpage Control
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Solution Overview
Problem
GaN crystal substrates with reduced warpage and surface roughness on the crystal growth surface are hindered by significant warpage and high surface roughness on the rear surface, leading to uneven heat distribution and poor semiconductor layer formation, which impairs the crystallinity and performance of semiconductor devices.
Innovation Solution
A GaN crystal substrate with a rear surface warpage of -35 µm ≤ w (R) ≤ 45 µm and surface roughness of Ra (R) ≤ 10 µm, achieved through precise measurement and processing techniques using laser displacement meters and Gaussian filters, combined with grinding, lapping, and etching methods, to ensure even heat distribution and improved crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the rear surface of the GaN crystal substrate has high surface roughness, then the manufacturing process is simpler, but the heat distribution becomes uneven and semiconductor layer formation is poor
Solution Approach 1:
The patent applies preliminary action by performing rear surface processing (grinding, lapping, and/or etching) before semiconductor layer formation. This ensures the rear surface has appropriate flatness and surface roughness (Ra(R) ≤ 10 µm, warpage w(R) within -35 µm to 45 µm) before the substrate is placed on the susceptor, preventing heat distribution issues during subsequent semiconductor layer formation.
2Manufacturing precision
If the rear surface warpage is large, then the substrate structure is easier to form, but the gap between substrate and susceptor increases causing uneven heat distribution
Solution Approach 1:
The patent applies parameter changes by controlling specific parameters of the rear surface: warpage w(R) within -35 µm to 45 µm and surface roughness Ra(R) ≤ 10 µm. These parameter specifications ensure optimal contact between the substrate and susceptor, achieving uniform heat distribution while maintaining structural integrity of the GaN crystal substrate.
3Manufacturing precision
If the crystal growth surface has reduced warpage and surface roughness, then the semiconductor layer quality improves, but the rear surface may have significant warpage and roughness
Solution Approach 1:
The patent applies local quality by differentiating the quality requirements for different surfaces of the GaN crystal substrate. The crystal growth surface is optimized for semiconductor layer formation with reduced warpage and surface roughness, while the rear surface is processed to have controlled flatness (warpage w(R) within -35 µm to 45 µm, Ra(R) ≤ 10 µm) for proper susceptor contact. This local differentiation allows each surface to fulfill its specific functional requirement.
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 results in stable and even semiconductor layer growth on the crystal growth surface, enhancing the properties and yield of semiconductor devices by optimizing the rear surface warpage and roughness, thereby improving the heating efficiency and crystallinity of the GaN crystal substrate.
Implementation Method 1
a plurality of displacement values respectively corresponding to a plurality of measurement points on the rear surface are detected using a laser displacement meter
Implementation Method 2
a plurality of displacement values for calculation are smoothed to calculate a warped surface
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
In a GaN crystal substrate (10), a rear surface (10r) opposite to a crystal growth surface (10c) can have a warpage w(R) satisfying -50 µm ≤ w(R) ≤ 50 µm, a surface roughness Ra(R) satisfying Ra(R) ≤ 10 µm, and a surface roughness Ry(R) satisfying Ry(R) ≤ 75 µm. Further, a method of manufacturing a semiconductor device (99) includes the step of preparing the GaN crystal substrate (10) as a substrate and growing at least one group-III nitride crystal layer (20) on a side of the crystal growth surface (10c) of the GaN crystal substrate (10). Thereby, a GaN crystal substrate having a rear surface with a reduced warpage and allowing a semiconductor layer having good crystallinity to be formed on a crystal growth surface thereof, a method of manufacturing the same, and a method of manufacturing a semiconductor device are provided.