Atmospheric Plasma Substrate Preparation for Epitaxial Growth
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Solution Overview
Problem
The preparation of semiconductor substrates for epitaxial growth is hindered by the difficulty in removing polishing residues and organic contamination without damaging the surface lattice, and the use of oxide passivation layers can introduce stress and imperfections due to non-stoichiometric growth and high desorption temperatures.
Innovation Solution
The use of downstream reactive components from an atmospheric plasma, specifically a reducing gas mixture like helium and hydrogen, to remove contaminants and create a pristine surface without mechanical damage, followed by controlled oxidation or nitridation to form a passivation layer that desorbs uniformly under modest heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional CMP polishing and high-temperature vacuum desorption are used to prepare substrate surfaces, then contamination removal is achieved, but surface lattice damage and process complexity increase
Solution Approach 1:
The patent replaces mechanical CMP polishing with atmospheric pressure plasma treatment to remove polishing residues and organic contamination. The plasma process uses reactive species and ion bombardment to chemically etch and remove contaminants without the mechanical forces that damage the surface lattice, thereby achieving contamination removal while preserving surface integrity.
Solution Approach 2:
The patent changes the temperature parameter from high-temperature vacuum desorption to room temperature or mildly heated atmospheric plasma processing. This parameter change allows effective contamination removal through plasma chemistry rather than thermal desorption, avoiding thermal damage to the surface lattice while maintaining cleaning effectiveness.
2Object-affected harmful factors
If oxide passivation layers are grown on substrate surfaces, then surface protection is achieved, but stress and non-stoichiometric imperfections are introduced
Solution Approach 1:
The patent extracts the oxide passivation step entirely from the process by using atmospheric pressure plasma to create a controlled surface environment that prevents oxidation during storage and transport. The plasma-treated surface forms a thin native oxide or hydroxide layer that is stoichiometric and free from the stress and imperfections associated with thermal oxide growth, thereby protecting the surface without compromising epitaxial layer quality.
Solution Approach 2:
The patent changes the oxidation method from high-temperature thermal oxide growth to low-temperature plasma-induced surface modification. This parameter change produces a thin, uniform, stoichiometric surface layer that provides protection without the stress and non-stoichiometric imperfections of thermally grown oxides, ensuring high epitaxial layer quality.
3Manufacturing precision
If high-vacuum epitaxial growth systems are used, then crystal quality is improved, but equipment cost and complexity increase
Solution Approach 1:
The patent replaces the high-vacuum mechanical system with an atmospheric pressure plasma system for surface preparation. By achieving contamination-free surfaces at atmospheric pressure, the need for complex high-vacuum equipment is reduced or eliminated, simplifying the overall system while maintaining the ability to produce high-quality epitaxial crystals through subsequent growth processes.
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 enables efficient removal of contaminants and passivation of the substrate surface, reducing defects and stress, thereby improving the quality and consistency of epitaxial layer growth while minimizing environmental impact and equipment costs.
Implementation Method 1
atmospheric plasma preparation steps
Implementation Method 2
downstream reactive components from an atmospheric plasma... to remove contaminants
Implementation Method 3
form a passivation layer that desorbs uniformly under modest heating
Data Source
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AI summary
After CMP and before an epitaxial growth step, the substrate is prepared by an atmospheric plasma which includes not only a reducing chemistry, but also metastable states of a chemically inert carrier gas. This removes residues, oxides, and/or contaminants. Optionally, nitrogen passivation is also performed under atmospheric conditions, to passivate the substrate surface for later epitaxial growth.