Strained-Silicon Transistor Fabrication via Ozone Cleaning
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Solution Overview
Problem
Conventional surface cleaning methods, such as using a sulfuric acid-hydrogen peroxide mixture, are not entirely effective in removing impurities like carbon, fluoride, and hydrogen atoms from semiconductor substrates, leading to defects and process inefficiencies in selective epitaxial growth for strained-silicon transistors.
Innovation Solution
Incorporating an in-situ oxygen flush or using a cleaning agent containing ozone, such as RCA Standard Clean I with ozone, to remove impurities and smooth the surface of recesses before selective epitaxial growth, ensuring improved quality and yield of the epitaxial layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional surface cleaning methods (sulfuric acid-hydrogen peroxide mixture) are used, then the cleaning process is simple and cost-effective, but impurities like carbon, fluoride, and hydrogen atoms remain on the surface, leading to defects in epitaxial layer formation
Solution Approach 1:
The patent changes the chemical parameters of the cleaning process by introducing ozone (O3) as a powerful oxidizing agent. The cleaning solution comprises ozone at a concentration of 0.1-10 ppm, hydrogen peroxide at 1-30%, and deionized water. This parameter change enables complete removal of organic and inorganic impurities including carbon, fluoride, and hydrogen atoms, thereby improving epitaxial layer quality without significantly increasing process complexity
Solution Approach 2:
The patent employs ozone, a strong oxidant, to accelerate the oxidation and removal of impurities from the semiconductor substrate surface. Ozone molecules (O3) are highly reactive and can oxidize organic contaminants and inorganic residues more effectively than conventional cleaning agents. This accelerated oxidation process ensures complete surface cleaning, preventing defects in the subsequent epitaxial growth process
2Manufacturing precision
If thorough surface cleaning is performed to remove all impurities, then the quality of epitaxial layer improves, but the cleaning process time and complexity increase
Solution Approach 1:
The patent performs preliminary surface preparation by conducting an in-situ oxygen plasma treatment before the wet cleaning step. This preliminary action activates the substrate surface and removes loose contaminants, making the subsequent ozone-based cleaning more efficient. By preparing the surface in advance, the overall cleaning time is reduced while achieving higher purity levels
Solution Approach 2:
The patent implements a continuous cleaning process where the ozone-based cleaning solution is circulated and regenerated in real-time. The cleaning process is designed to maintain optimal ozone concentration and flow rate throughout, ensuring continuous effective cleaning without interruptions. This continuous action achieves complete impurity removal in a single step, reducing total process time
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 proposed method effectively removes residual impurities and smoothens the surface, enhancing the selective epitaxial growth process and reducing defects, thereby improving the fabrication of strained-silicon transistors.
Implementation Method 1
utilizing a cleaning agent containing ozone to perform a cleaning process for removing the remaining etching particles from the surface of the semiconductor substrate
Implementation Method 2
performing a selective epitaxial growth (SEG) to form an epitaxial layer in each recess for forming a source/drain region
Data Source
AI summary
A method of fabricating strained-silicon transistors includes providing a semiconductor substrate, in which the semiconductor substrate contains a gate structure thereon; performing an etching process to form two recesses corresponding to the gate structure within the semiconductor substrate; performing an oxygen flush on the semiconductor substrate; performing a cleaning process on the semiconductor substrate; and performing a selective epitaxial growth (SEG) to form an epitaxial layer in each recess for forming a source/drain region.