Epitaxial Surface Preparation Using Cyclic Halogen Removal
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Solution Overview
Problem
Existing methods for surface preparation in semiconductor manufacturing, such as plasma etching and chemical mechanical polishing, often result in damaged surfaces and fail to address strain formation due to lattice mismatch between dissimilar materials.
Innovation Solution
A cyclic removal process that modifies the top-most surface layer by introducing halogen species, followed by activation to form volatile products, effectively removes impurities and defects, and is combined with an optional deposition process to overgrow impurities and defects, ensuring a clean and smooth surface for epitaxial material growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma etching is used for surface preparation, then surface roughness is reduced, but the surface becomes damaged due to ion bombardment and VUV irradiation
Solution Approach 1:
The patent replaces the mechanical/physical bombardment mechanism of plasma etching with a purely chemical mechanism. The surface is modified by introducing halogen species (such as chlorine or bromine) that chemically react with surface atoms to form volatile compounds, which are then removed by evacuation. This chemical approach eliminates the damaging ion bombardment and VUV irradiation while still achieving surface smoothing and impurity removal.
Solution Approach 2:
The patent changes the fundamental mechanism parameter from physical/chemical to purely chemical. By using halogen species introduction and thermal activation instead of plasma bombardment, the process parameters shift from high-energy physical conditions to controlled chemical reactions at lower energies, thereby removing the harmful effects while maintaining the beneficial surface preparation outcomes.
2Manufacturing precision
If CMP is used for surface preparation, then surface is smoothed, but the topmost material surface layer is damaged due to mechanical force
Solution Approach 1:
The patent replaces the mechanical polishing action of CMP with a chemical process. Instead of using abrasive particles and mechanical pressure to remove material, the invention uses halogen species to chemically modify the surface layer, forming volatile products that are subsequently evacuated. This substitution eliminates mechanical damage to the topmost surface layer while achieving equivalent or superior smoothing results.
3Reliability
If conventional surface preparation methods are used, then surface is cleaned, but strain formation occurs due to lattice mismatch between dissimilar materials
Solution Approach 1:
The patent performs preliminary surface modification before the actual epitaxial growth of dissimilar materials. By introducing halogen species and activating the surface to form volatile products, the process prepares the surface in advance to be more compatible with the incoming material layer. This preliminary chemical treatment reduces the abruptness of the interface between dissimilar materials, thereby mitigating strain formation and improving the reliability of the grown layer.
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 achieves a significant reduction in surface roughness and defects, leading to high-quality epitaxial material growth, particularly for dissimilar materials, thereby enhancing the performance and reliability of semiconductor devices.
Implementation Method 1
modifying a top-most surface layer of the surface by introducing a chemical species, such as halogens
Implementation Method 2
activating the top-most modified surface layer to form volatile products
Implementation Method 3
The method achieves a significant reduction in surface roughness and defects, leading to high-quality epitaxial material growth
Implementation Method 4
a deposition process to overgrow impurities and defects on the surface
Data Source
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AI summary
A method of preparing a surface of a substrate and epitaxial material growth is disclosed. The method includes exposing the surface to a cyclic removal process to remove impurities and defects from the surface. This process involves modifying a top-most surface layer of the surface by introducing a chemical species, such as halogens, in a process chamber volume enclosing the substrate, to obtain a top-most modified surface layer of the surface. The method also includes evacuating excessive chemical species from the process chamber volume, activating the top-most modified surface layer to form volatile products, and optionally removing etch products from the process chamber volume. The cyclic removal process is followed by epitaxial material growth, wherein the growth material is different from the material of the surface.