Cryogenic Silicon Oxide ALE Without Polymer Residues
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Solution Overview
Problem
Conventional atomic layer etching (ALE) processes using greenhouse gases result in fluorocarbon film deposition, leading to polymer formation and corner residues on high-aspect ratio structures, necessitating additional steps like overetch or declog to address clogging, and are environmentally unfriendly.
Innovation Solution
A carbon-free fluorine-containing gas is used to convert exposed silicon-containing layers to reactive portions, followed by etching with a plasma formed from an inert gas, eliminating the need for additional steps and reducing environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ALE uses fluorocarbon-containing greenhouse gases to etch silicon oxide, then etching capability is achieved, but polymer deposition occurs on the surface leading to corner residues and clogging in high-aspect ratio structures
Solution Approach 1:
The patent extracts and removes the carbon component from the fluorocarbon gas, using pure fluorine-containing gases (SF6, CF4, C2F6) that do not form polymer deposits. This eliminates the harmful polymer deposition while preserving the etching capability through fluorine's high reactivity with silicon oxide.
Solution Approach 2:
The patent changes the chemical composition parameter of the etching gas from fluorocarbon-containing to pure fluorine-containing, and adjusts the temperature parameter to cryogenic range (-50°C to -150°C). These parameter changes prevent polymer formation while maintaining effective etching of silicon oxide.
2Productivity
If conventional ALE uses fluorocarbon gases to maintain etching performance, then etching speed is maintained, but additional overetch or declog steps are required to remove corner residues
Solution Approach 1:
By removing carbon from the gas composition, the patent eliminates polymer deposition at the source, making additional declog steps unnecessary. The process achieves complete etching in a single step without requiring subsequent cleanup operations.
Solution Approach 2:
The fluorine-containing gas performs the etching function self-sufficiently without generating polymer byproducts that would require additional processing. The process is self-cleaning in nature, eliminating the need for separate overetch or declog steps.
3Productivity
If fluorocarbon gases are used in ALE processes, then etching of silicon oxide is achieved, but greenhouse gas emissions and environmental pollution occur
Solution Approach 1:
The patent extracts and eliminates the carbon component from the etching gas, using pure fluorine-containing gases that do not contribute to greenhouse effects. This removes the environmental harm while preserving the etching functionality through fluorine's chemical reactivity.
Solution Approach 2:
The patent changes the gas composition parameter to exclude carbon entirely, using SF6, CF4, or C2F6 which have different environmental characteristics. Combined with cryogenic temperature control, this creates an environmentally friendly etching process that maintains high etching performance.
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 etches high-aspect ratio structures without polymer deposition, reduces corner residues, and maintains environmental safety by avoiding greenhouse gases, thus improving etch results and process efficiency.
Implementation Method 1
exposing a portion of a silicon containing layer formed over the substrate through an opening formed though a masking layer to a carbon-free fluorine containing gas to convert the exposed portion of the silicon containing layer to a reactive portion
Implementation Method 2
etching the reactive portion by exposing the reactive portion of the silicon containing layer to a plasma formed from an inert gas
Implementation Method 3
Atomic layer etching (ALE) of silicon oxide at cryogenic temperature
Data Source
AI summary
Embodiments of the disclosure include a method for forming a feature on a substrate includes exposing a portion of a silicon containing layer formed over the substrate through an opening formed though a masking layer to a carbon-free fluorine containing gas to convert the exposed portion of the silicon containing layer to a reactive portion, and etching the reactive portion by exposing the reactive portion of the silicon containing layer to a plasma formed from an inert gas.