Semiconductor Surface Cleaning with Fluorine Radicals
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Solution Overview
Problem
Conventional semiconductor device fabrication methods face challenges such as incomplete removal of water marks and oxide films, contamination from atmospheric exposure, and damage from plasma-based cleaning techniques, which affect film deposition and device performance, especially with the miniaturization of devices requiring lower temperature processing.
Innovation Solution
A method involving surface cleaning with fluorine or hydrogen radicals followed by hydrogen termination and sputter film deposition in a vacuum environment, allowing for the formation of dielectric films like HfO, HfON, and HfN without carbon, moisture, or metal impurities, and subsequent plasma oxidation or nitridation to achieve high-quality semiconductor/insulator junctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If reverse sputtering method using argon plasma is used for dry cleaning, then oxide film removal is improved, but Si-Si bond breaking occurs causing surface damage and contaminant adhesion
Solution Approach 1:
The patent changes the cleaning mechanism from physical sputtering to chemical reaction by using fluorine radicals instead of argon plasma. The fluorine radicals chemically react with and remove oxide films without breaking Si-Si bonds, thus achieving oxide removal while preventing surface damage and contaminant adhesion.
Solution Approach 2:
The patent replaces the mechanical sputtering process with a chemical cleaning process. Instead of using physical bombardment by argon ions to remove oxides, fluorine radicals are used to chemically etch and remove oxide films, eliminating the mechanical damage caused by sputtering.
2Manufacturing precision
If H radical cleaning is used to remove fluorine residue, then F removal is improved, but metallic contamination and overetching occur
Solution Approach 1:
The patent introduces hydrogen radicals as an intermediary substance to remove fluorine residues. The hydrogen radicals selectively react with fluorine atoms on the silicon surface to form HF, which then desorbs from the surface. This intermediary approach allows F removal without the harmful effects of metallic contamination and overetching associated with H radical cleaning.
Solution Approach 2:
The patent changes the cleaning chemistry by using fluorine radicals for oxide removal followed by hydrogen radicals for fluorine residue removal. This two-step chemical process with controlled parameters achieves complete F removal while avoiding the contamination and overetching problems of conventional H radical cleaning.
3Ease of operation
If wet cleaning is used for substrate cleaning, then ease of operation is improved, but water mark formation and incomplete oxide removal occur
Solution Approach 1:
The patent replaces wet chemical cleaning with plasma-based dry cleaning using fluorine radicals. This substitution eliminates water mark formation and enables complete oxide film removal while maintaining ease of operation through automated plasma processing. The dry cleaning process also allows for better control of the cleaning chemistry and parameters.
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 approach enables the formation of high-quality dielectric films with reduced interface states and fixed charges, improved reproducibility, and minimized metallic contamination, leading to favorable device characteristics such as reduced leakage current and hysteresis in C-V curves.
Implementation Method 1
a first step of removing a native oxide film formed on an Si substrate by surface cleaning processing in which the semiconductor substrate is exposed to an atmosphere having a fluorine radical
Implementation Method 2
a second step of exposing the surface terminated with fluorine to a hydrogen radical atmosphere
Implementation Method 3
exposed to an atmosphere having a fluorine radical generated using F2 (gas not containing hydrogen) or the step of exposing the semiconductor substrate to an atmosphere having a fluorine radical generated using an HF gas (gas containing hydrogen)
Implementation Method 4
performing sputter film deposition of any one of various dielectric materials
Implementation Method 5
performing plasma oxidation or nitridation to achieve high-quality semiconductor/insulator junctions
Data Source
AI summary
A dielectric insulating film including HfO or the like is formed by: cleaning a surface of a semiconductor substrate by exposing the substrate surface to a fluorine radical; performing hydrogen termination processing with a fluorine radical or a hydride (SiH4 or the like); sputtering Hf or the like; and then performing oxidation/nitridation. These steps are carried out without exposing the substrate to atmosphere, thereby making it possible to obtain a C-V curve with less hysteresis and realize a MOS-FET having favorable device characteristics.