HF Plasma Etching for High-Aspect-Ratio Silicon Oxide
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Solution Overview
Problem
Existing plasma etching methods face challenges in efficiently etching silicon oxide films with high aspect ratios due to reduced etchant supply as the etching progresses, leading to decreased etching rates.
Innovation Solution
A plasma etching method involving the use of hydrogen fluoride gas with a volume flow ratio of 30% or more, combined with maintaining the substrate temperature at 0°C or lower, to enhance etchant supply and etching efficiency, particularly through the formation of a condensed or solidified hydrogen fluoride layer at the etching shape's bottom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If plasma etching is performed on silicon oxide film to form high aspect ratio structures, then the etching depth and aspect ratio are improved, but the etchant supply decreases as etching progresses
Solution Approach 1:
The patent changes the chemical composition parameters of the processing gas by introducing hydrogen fluoride gas at a specific volume flow ratio (30% or more), which fundamentally alters the etching chemistry to enable sustained etchant supply throughout the etching process, resolving the contradiction between achieving deep etching and maintaining adequate etchant supply
Solution Approach 2:
The patent utilizes the phase transition of hydrogen fluoride gas to condensed or solidified layer formation at the bottom of the etching shape. This phase transition creates a reservoir of etchant that continuously supplies reactive species to the etching front, maintaining etching rate even as the aspect ratio increases and gas-phase etchant supply would normally diminish
2Length of moving object
If etching progresses in high aspect ratio structures, then the recess depth increases, but the etching rate decreases due to reduced etchant supply
Solution Approach 1:
The patent performs preliminary action by forming a condensed or solidified layer of hydrogen fluoride at the bottom of the etching shape before the main etching process. This pre-formed layer acts as an etchant reservoir that ensures continuous supply of reactive species during subsequent etching, preventing the decline in etching rate that would normally occur as recess depth increases
Solution Approach 2:
The patent changes the physical state parameters of the etchant by controlling temperature (0°C or lower) and chemical composition (hydrogen fluoride gas with 30% or more volume flow ratio), transforming the etchant from a gas-phase only system to one that utilizes condensed/solidified phase for sustained supply, thereby maintaining constant etching rate throughout the process
3Ease of manufacture
If conventional plasma etching is used with fluorocarbon or hydrofluorocarbon gas, then the etching process can be performed, but the etchant supply becomes insufficient at high aspect ratios
Solution Approach 1:
The patent fundamentally changes the chemical composition parameter of the processing gas from conventional fluorocarbon or hydrofluorocarbon gases to hydrogen fluoride gas with a volume flow ratio of 30% or more. This parameter change enables the formation of condensed or solidified hydrogen fluoride layers that provide sustained etchant supply, resolving the insufficiency problem while maintaining processability
Solution Approach 2:
The patent introduces hydrogen fluoride gas as an intermediary substance that forms condensed or solidified layers at the etching front. This intermediary acts as a bridge between the gas-phase plasma and the silicon oxide film, providing continuous supply of reactive fluorine species even in high aspect ratio structures where direct gas-phase transport would be insufficient
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 improves etching rates by ensuring consistent etchant supply and reaction at the etching shape's bottom, even at high aspect ratios, thereby enhancing the etching process efficiency.
Implementation Method 1
forming a condensed or solidified layer of HF at the bottom of the etching shape
Implementation Method 2
forming a condensed or solidified layer of HF at the bottom of the etching shape
Implementation Method 3
a cooler configured to maintain the support at 0° C. or lower during generation of the plasma
Implementation Method 4
a plasma generator configured to generate a plasma from the processing gas in the chamber to etch the substrate with the plasma
Data Source
AI summary
A plasma etching apparatus includes: a chamber; a support configured to support a substrate in the chamber; a gas supply configured to supply a processing gas into the chamber, the processing gas including hydrogen fluoride gas with a volume flow ratio of 30% or more with respect to a total flow rate of the processing gas; a plasma generator configured to generate a plasma from the processing gas in the chamber to etch the substrate with the plasma; and a cooler configured to maintain the support at 0° C. or lower during generation of the plasma.