Substrate Surface Cleaning via Sacrificial Oxide Growth
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Solution Overview
Problem
Existing methods for removing native oxides and contaminants from semiconductor substrate surfaces are not effective, leading to suboptimal quality of epitaxial layers due to residual contaminants.
Innovation Solution
Exposing the substrate to an oxidizing source to increase the thickness of the oxide layer, which then encompasses and removes contaminants, followed by a thermal process to clean the surface, allowing for the formation of a high-quality epitaxial layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional cleaning methods are used to remove native oxides and contaminants, then some contaminants are removed, but residual contaminants remain on the substrate surface
Solution Approach 1:
The patent applies preliminary action by intentionally forming an additional oxide layer on the substrate surface before epitaxial growth. This sacrificial oxide layer is created through thermal oxidation or plasma oxidation, then selectively removed to expose a clean substrate surface free of contaminants that would otherwise remain after conventional cleaning
Solution Approach 2:
The patent employs strong oxidants by using plasma oxidation with reactive species such as oxygen plasma, ozone plasma, or nitric oxide plasma to rapidly form and thickening the oxide layer. These highly reactive oxidizing sources enable controlled formation of substantial oxide layers that can be subsequently removed to reveal ultra-clean surfaces
2Manufacturing precision
If the oxide layer thickness is increased to remove more contaminants, then more contaminants are removed, but the removal process becomes more complex
Solution Approach 1:
The patent merges multiple functions into a single integrated process sequence: oxide layer formation through oxidation, contaminant entrapment within the oxide, and selective removal through etching. This combination of steps achieves superior cleaning effectiveness while managing process complexity through systematic integration
Solution Approach 2:
The patent applies parameter changes by controlling oxidation conditions (temperature, time, oxidizing atmosphere) to form oxide layers of specific thicknesses, and by adjusting etching parameters to selectively remove the oxide layer with trapped contaminants while preserving the underlying substrate and any desired epitaxial layers
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 method significantly reduces interfacial contamination, resulting in cleaner substrate surfaces and improved quality of subsequently deposited epitaxial layers with enhanced uniformity and performance.
Implementation Method 1
exposing the substrate to an oxidizing source. The oxidizing source oxidizes an upper portion of the substrate beneath the oxide layer to form an oxide layer having an increased thickness
Implementation Method 2
The thickness of the native oxide layer is increased by exposing the substrate to an oxidizing source selected form the group consisting of oxygen, ozone, and steam. The substrate is positioned in a second chamber, and the oxide layer is removed from the substrate during a thermal process
Data Source
AI summary
Embodiments of the present invention generally relate to methods for removing contaminants and native oxides from substrate surfaces. The methods generally include exposing a substrate having an oxide layer thereon to an oxidizing source. The oxidizing source oxidizes an upper portion of the substrate beneath the oxide layer to form an oxide layer having an increased thickness. The oxide layer with the increased thickness is then removed to expose a clean surface of the substrate. The removal of the oxide layer generally includes removal of contaminants present in and on the oxide layer, especially those contaminants present at the interface of the oxide layer and the substrate. An epitaxial layer may then be formed on the clean surface of the substrate.