SOI Substrate Surface Flattening via Pre-Cleaning and Vapor-Phase Etching
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Solution Overview
Problem
Conventional methods for manufacturing SOI substrates using vapor-phase etching result in microprotrusions on the surface due to residual organic substances and native oxide films, leading to surface roughness and crystal defects, which are not effectively addressed by existing cleaning processes.
Innovation Solution
A method that involves removing organic substances from the surface using ozone water, sulfuric acid, plasma of oxygen gas, or radicals of oxygen gas before vapor-phase etching, followed by the use of hydrofluoric acid to remove native oxide films, ensuring complete removal and preventing microprotrusions and cracked particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If vapor-phase etching is performed directly after bonding without removing organic substances, then the process is simple, but microprotrusions occur on the surface due to residual organic substances and native oxide films
Solution Approach 1:
The patent applies preliminary action by removing organic substances and native oxide films from the semiconductor substrate surface before performing vapor-phase etching. This pre-cleaning step ensures that the etching process operates on a clean surface, preventing microprotrusions and achieving the desired surface flatness without compromising process simplicity
Solution Approach 2:
The patent segments the surface preparation process into distinct steps: first removing organic substances, then removing native oxide films, and finally performing vapor-phase etching. This segmentation allows each step to be optimized independently, ensuring complete removal of contaminants while maintaining overall process efficiency and surface quality
2Ease of manufacture
If conventional cleaning methods are used, then the process is simple, but crystal defect layers exist in the upper portion of the SOI layer
Solution Approach 1:
The patent replaces conventional mechanical cleaning methods with vapor-phase etching, which uses chemical reactions to remove surface contaminants and crystal defect layers. This substitution achieves superior crystal quality by eliminating defect layers that conventional cleaning cannot remove, while maintaining process simplicity through a single integrated etching step
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 method effectively flattens the surface of the active layer without generating microprotrusions, reducing surface roughness and crystal defects, and prevents the formation of cracked particles by ensuring thorough removal of organic substances and native oxide films.
Implementation Method 1
removing the organic substance adhering onto the surface of the active layer by cleaning using dissolved ozone water, sulfuric acid, plasma of oxygen gas, or radical of oxygen gas
Implementation Method 2
plasma of oxygen gas, or radical of oxygen gas
Implementation Method 3
the native oxide film which is formed on the surface of the active layer is removed
Implementation Method 4
the surface of the active layer is flattened by the vapor-phase etching
Implementation Method 5
vapor-phase etching process because reactive gas, such as SF 6 , CF 4 , H 2 , etc. used in the vapor-phase etching treatment
Data Source
Figure 1(a)~1(h)
Figure 2(a)~2(h)
Figure 3(a)~3(g)
AI summary
A high quality bonded substrate is obtained in which generation of microprotrusions and cracked particles are restricted on a surface of an active layer of the bonded substrate and the surface of the active layer is flattened. A laminated body is formed by overlapping a first semiconductor substrate serving as an active layer onto a second semiconductor substrate serving as a support substrate via an oxide film or without an oxide film; the active layer is formed by forming a thin film from the first semiconductor substrate; and the surface of the active layer is flattened by vapor-phase etching. After forming a thin film from the first semiconductor substrate and before flattening the surface of the active layer by the vapor-phase etching, an organic substance adhering to the surface of the active layer is removed and a native oxide film generated on the surface of the active layer is removed after removing the organic substance.