HF Vapor Etching Cleanup Using Si-F Infrared Endpoint Detection
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Solution Overview
Problem
Conventional etching methods using hydrofluoric acid vapor leave residual fluorine on silicon surfaces, leading to defects and particle formation, and the timing for effective cleaning is difficult to determine, resulting in prolonged cleaning processes.
Innovation Solution
An etching method and apparatus that creates a reduced pressure state, uses hydrogen fluoride gas to etch the coating film, and employs infrared spectroscopy to detect Si—F stretching vibration for precise timing of cleaning with vapor, ensuring residual fluorine removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If vapor-phase etching using hydrofluoric acid is used to etch silicon oxide films, then etching capability is improved, but residual fluorine remains on the silicon surface causing defects and particle formation
Solution Approach 1:
The patent extracts and removes the harmful residual fluorine from the silicon surface after etching by introducing a cleaning gas flow that selectively removes fluorine-containing byproducts while preserving the silicon substrate and etched features
Solution Approach 2:
The patent converts the harmful residual fluorine into a removable byproduct by controlling the etching process to produce fluorine-containing volatile compounds that can be easily evacuated, transforming the contamination problem into a manageable removal process
2Reliability
If cleaning process is prolonged to ensure sufficient fluorine removal, then substrate purity is improved, but processing time increases unnecessarily
Solution Approach 1:
The patent introduces real-time monitoring of the cleaning process by detecting the evolution of fluorine-containing byproducts, using this feedback information to dynamically adjust and terminate the cleaning process at the optimal moment when sufficient purification is achieved without unnecessary delay
Solution Approach 2:
The patent employs dynamic control of the cleaning process parameters including gas flow rate, temperature, and pressure, adjusting these variables in real-time based on the detected fluorine removal rate to optimize both cleaning effectiveness and process efficiency
3Reliability
If right timing for cleaning is difficult to determine, then substrate purity may be improved, but process efficiency deteriorates due to prolonged cleaning
Solution Approach 1:
The patent replaces the mechanical/time-based cleaning control with an analytical detection system that monitors the chemical composition of the gas phase, using spectroscopic or mass spectrometric methods to detect fluorine-containing byproducts and provide real-time feedback on cleaning progress
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 effectively removes residual fluorine without unnecessary prolongation of the cleaning process, maintaining high efficiency and preventing substrate defects.
Implementation Method 1
detecting Si—F stretching vibration in the substrate by infrared spectroscopy
Implementation Method 2
cleaning the substrate by supplying vapor into the processing chamber
Implementation Method 3
supplying an etching gas containing hydrogen fluoride into the processing chamber and etching the coating film
Data Source
AI summary
An etching method according to the present invention includes after a step of creating a reduced pressure state, a step of supplying an etching gas containing hydrogen fluoride into a processing chamber and etching a coating film formed on a substrate, after the step of etching the coating film, a step of cleaning the substrate by supplying vapor into the processing chamber, and in the step of cleaning the substrate, a step of detecting Si—F stretching vibration in the substrate by infrared spectroscopy, in which the step of cleaning the substrate ends when the Si—F stretching vibration equal to or lower than a predetermined first threshold value is detected. Therefore, the time required for cleaning the substrate is prevented from being unnecessarily long.