Inert Gas Plasma Moisture Removal for Fluorine Etching
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Solution Overview
Problem
The existing etching methods for semiconductor wafers using fluorine-based gases face challenges with moisture-induced hydrofluoric acid production, which is hazardous and corrosive, requiring lengthy drying processes and risk of re-moisturizing during transfer, necessitating additional acid removal processes.
Innovation Solution
An etching method involving a moisture removal step using an inert gas plasma to convert moisture into a gas phase within a vacuum chamber, followed by dry etching with a fluorine-based gas plasma, eliminating the need for pre-drying and preventing hydrofluoric acid production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If spin drying by dry air is performed to dry the workpiece, then the workpiece can be dried, but the drying time is long
Solution Approach 1:
The patent replaces the mechanical spin drying system with a plasma-based moisture removal system. Instead of using mechanical centrifugal force to remove moisture, the invention uses plasma generated from inert gas to chemically react with and remove moisture molecules from the workpiece surface, dramatically reducing drying time from minutes to seconds.
Solution Approach 2:
The patent changes the physical and chemical parameters of the gas environment to achieve rapid moisture removal. By introducing inert gas and generating plasma (changing from thermal to non-thermal energy state), the system achieves efficient moisture removal without the mechanical constraints of traditional drying methods.
2Reliability
If the workpiece is loaded to the etching apparatus after cleaning, then the etching process can proceed, but moisture may adhere to the workpiece during transfer
Solution Approach 1:
The patent merges the drying process and etching process into a single integrated chamber. The workpiece undergoes both moisture removal and etching without being transferred to another chamber, eliminating the risk of moisture re-adhesion during transfer and simplifying the overall process flow.
Solution Approach 2:
The patent uses inert gas plasma as an intermediary medium that serves dual purposes: it removes moisture from the workpiece surface and creates a controlled atmosphere that prevents moisture re-adhesion. This intermediary plasma environment bridges the gap between cleaning and etching processes.
3Manufacturing precision
If fluorine-based stable gas is used for etching, then dry etching can be performed, but hydrofluoric acid is produced when the gas reacts with moisture
Solution Approach 1:
The patent performs moisture removal as a preliminary action before introducing the fluorine-based etching gas. By removing moisture first using inert gas plasma, the system prevents the formation of hydrofluoric acid during the subsequent etching process, eliminating the need for additional acid removal equipment.
Solution Approach 2:
The patent converts the potentially harmful reaction between fluorine-based gas and moisture into a beneficial process. By controlling the sequence of operations and using plasma activation, the system ensures that the fluorine-based gas only reacts with the workpiece surface for precise etching, while any incidental moisture reaction is prevented from producing harmful hydrofluoric acid.
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 effectively reduces drying time, prevents hydrofluoric acid production, and eliminates the need for post-etching acid removal equipment by drying and etching the workpiece in a continuous chamber process.
Implementation Method 1
dissociating the inert gas under first processing conditions to form a first plasma and thereby remove moisture present on the workpiece
Implementation Method 2
dissociating the inert gas under first processing conditions to form a first plasma
Implementation Method 3
dissociating the fluorine-based stable gas under second processing conditions to form a second plasma and thereby dry-etch the workpiece
Implementation Method 4
dissociating the fluorine-based stable gas under second processing conditions to form a second plasma
Data Source
AI summary
Disclosed herein is an etching method for a workpiece. The etching method includes the steps of dissociating an inert gas to form a plasma in an evacuated condition of a chamber to thereby remove moisture present on the workpiece set in the chamber, and next dissociating a fluorine-based stable gas instead of the inert gas to form a plasma in the chamber after removing the moisture to thereby dry-etch the workpiece.