Ruthenium Hard Mask Etching with DLC Protection for Selectivity
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Solution Overview
Problem
Existing etching methods using hard mask films containing ruthenium face challenges in achieving sufficient selectivity with respect to etching target films, particularly in high aspect ratio trenches or holes, necessitating further improvement in mask film selectivity.
Innovation Solution
An etching method involving a plasma processing system that uses a mask film containing ruthenium and supplies a mixture of hydrocarbon and fluorine-containing gases, generating plasma to etch a silicon-containing film, where the ruthenium content in the mask film is 20% or more, and the hydrocarbon gas flow rate is 50% or less, forming a protective diamond-like carbon layer on the mask film surface to enhance selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hard mask film containing ruthenium is used for etching, then the mask film can be formed with good adhesion and pattern fidelity, but the selectivity between the mask film and the silicon-containing etch layer is insufficient
Solution Approach 1:
The patent uses a composite mask film structure consisting of a ruthenium-containing lower mask film layer (providing adhesion and pattern fidelity) and a carbon-containing upper mask film layer (providing high etching selectivity). This composite structure combines the advantages of both materials to resolve the contradiction between adhesion and selectivity.
Solution Approach 2:
The patent applies different material compositions to different layers of the mask film structure. The lower layer uses ruthenium-based material for adhesion-critical regions, while the upper layer uses carbon-based material for selectivity-critical regions. This local differentiation of material properties resolves the contradiction.
2Stability of the object's composition
If the ruthenium content in the mask film is increased to improve adhesion, then the mask film stability improves, but the etch rate of the mask film increases reducing selectivity
Solution Approach 1:
The patent segments the mask film into functionally distinct layers: a ruthenium-containing lower layer for stability and adhesion, and a carbon-containing upper layer for selective etching protection. This segmentation allows each layer to optimize its specific function without compromising the other.
Solution Approach 2:
By creating a composite mask film with ruthenium in the lower layer and carbon in the upper layer, the patent achieves both high stability (from ruthenium) and high selectivity (from carbon's low etch rate). The composite structure resolves the contradiction between stability and selectivity.
3Productivity
If a plasma etching process is used to achieve high aspect ratio trenches, then the etching depth and speed improve, but the mask film selectivity deteriorates
Solution Approach 1:
The carbon-containing upper mask film layer provides exceptional resistance to plasma etching due to carbon's inherently low reactivity with fluorine-based plasma. This allows the use of aggressive plasma etching conditions for high aspect ratio trenches while the carbon layer maintains mask integrity and selectivity.
Solution Approach 2:
The patent applies carbon-based material specifically in the upper mask film layer where plasma resistance is most critical for high aspect ratio etching. This localized application of carbon's plasma-resistant property enables high productivity plasma etching while maintaining selectivity.
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 the selectivity of the mask film, reducing its etch rate relative to the silicon-containing film, achieving etch rates of silicon oxide and silicon nitride films that are 100 and 20 times greater, respectively, while forming a protective film on the mask film surface.
Implementation Method 1
etching the silicon-containing film through the mask film using plasma generated from the process gas supplied into the chamber
Implementation Method 2
forming a protective diamond-like carbon layer on the mask film surface to enhance selectivity
Data Source
AI summary
An etching method includes: a) preparing, within a chamber, a substrate including a mask film containing ruthenium and having a predetermined pattern formed in the mask film, and a silicon-containing film provided under the mask film; b) supplying a process gas including a hydrocarbon-containing gas and a fluorine-containing gas into the chamber; and c) etching the silicon-containing film through the mask film using plasma generated from the process gas supplied into the chamber.