Selective Mo/W Etching Using Oxidation and Hexafluoride Gases
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Solution Overview
Problem
Existing etching methods struggle to achieve high selectivity when etching molybdenum (Mo) or tungsten (W) films relative to silicon-containing films, which is crucial for semiconductor storage devices.
Innovation Solution
The method involves providing a substrate with a silicon-containing material and an exposed Mo or W film, and then selectively etching the Mo or W film using an oxidation gas and a hexafluoride gas as etching gases, achieving high selectivity by controlling the etching conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma etching using Cl2 gas, O2 gas, and N2 gas is used to selectively etch tungsten film relative to silicon-containing film, then etching can be performed, but the etching selectivity is insufficient
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using oxidation gas (O2, N2O, or O3) combined with hexafluoride gas (WF6, MoF6, or SF6) instead of conventional plasma etching gases. This parameter change enables highly selective etching of W or Mo films relative to silicon-containing films, achieving selectivity of 50 or more, which cannot be attained with traditional plasma etching methods.
Solution Approach 2:
The patent employs strong oxidants (oxidation gases such as O2, N2O, or O3) to oxidize the W or Mo film surface before etching. This oxidation step creates a reactive oxide layer that enhances the selectivity of subsequent fluorine-based etching, allowing differential etching between the conductor film and silicon-containing films with selectivity exceeding 450 in some cases.
2Manufacturing precision
If conventional plasma etching methods are used, then etching process can be implemented, but etching selectivity of 50 or more cannot be achieved
Solution Approach 1:
The patent performs preliminary oxidation of the W or Mo film surface using oxidation gas before the actual etching step. This preliminary action creates a chemically modified surface that is highly susceptible to selective fluorine-based etching, enabling achievement of etching selectivity of 50 or more, which is not attainable with direct plasma etching methods.
Solution Approach 2:
The patent introduces oxidation gas as an intermediary substance that mediates between the etching gas and the conductor film. The oxidation gas creates a reactive oxide layer on the W or Mo film surface, which then reacts selectively with the hexafluoride gas, enabling high selectivity etching that cannot be achieved through direct plasma etching alone.
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 allows for high selectivity etching of Mo or W films relative to silicon-containing materials, achieving etching selectivity of 50 or more, and in some cases, exceeding 450, which is not attainable with traditional plasma etching methods.
Implementation Method 1
supplying, into the chamber, an oxidation gas and a hexafluoride gas as an etching gas
Implementation Method 2
selectively etching the molybdenum film or the tungsten film relative to the silicon-containing material by supplying, into the chamber, an oxidation gas and a hexafluoride gas as an etching gas
Data Source
AI summary
An etching method includes: providing, within a chamber, a substrate that includes at least a silicon-containing material and a molybdenum film or a tungsten film which is in an exposed state, and selectively etching the molybdenum film or the tungsten film relative to the silicon-containing material by supplying, into the chamber, an oxidation gas and a hexafluoride gas as an etching gas.