Hard Mask Stack for High-Aspect-Ratio Silicon Etching
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Solution Overview
Problem
In the manufacturing of electronic devices, particularly semiconductor devices, the existing hard masks used for plasma etching of silicon-containing films are inadequate for forming deep, high-aspect-ratio openings without significant shape abnormality and twisting.
Innovation Solution
A method involving the use of a hard mask with a first film containing tungsten and a second film containing zirconium or titanium and oxygen, where the second film provides higher etching resistance, allowing for the formation of patterns with reduced shape abnormality and twisting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional hard mask (tungsten silicide or TiN) is used for plasma etching of silicon-containing film, then the mask provides basic etching resistance, but significant shape abnormality and twisting occur in deep, high-aspect-ratio openings
Solution Approach 1:
The hard mask is divided into two distinct films: a first hard mask film (tungsten silicide or TiN) and a second hard mask film (metal oxide). This segmentation allows each film to perform specialized functions - the first film provides foundational etching resistance while the second film with higher etching resistance prevents shape abnormality and twisting during plasma etching of deep patterns
Solution Approach 2:
The patent uses a composite mask structure combining two different materials with complementary properties. The first hard mask film (tungsten silicide or TiN) is combined with a second hard mask film (metal oxide such as silicon oxide, silicon nitride, or titanium nitride). This composite structure leverages the high etching resistance of the metal oxide to suppress pattern distortion while maintaining the beneficial properties of the underlying tungsten silicide or TiN layer
2Manufacturing precision
If the hard mask thickness is increased to reduce shape abnormality in deep openings, then pattern fidelity improves, but the etching process becomes more complex and requires additional mask layers
Solution Approach 1:
Rather than increasing the thickness of a single hard mask layer, the patent segments the mask function into two separate films with different thicknesses and properties. The first hard mask film has a thickness of 50-200 nm while the second hard mask film has a thickness of 10-50 nm, allowing optimized performance without excessive total thickness
Solution Approach 2:
The patent changes the material composition parameter of the hard mask system by introducing a metal oxide layer with fundamentally different etching characteristics. This parameter change enables the second film to provide superior etching resistance during plasma etching, improving pattern fidelity without requiring excessive total mask thickness
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 proposed method effectively suppresses shape abnormality and twisting in high-aspect-ratio patterns formed on silicon-containing films, even when the patterns have critical dimensions of 20 nm or less and depths of 1.0 μm or more.
Implementation Method 1
the second film provides higher etching resistance, allowing for the formation of patterns with reduced shape abnormality and twisting
Data Source
AI summary
A method of processing a wafer includes preparing a wafer having a substrate and a silicon-containing film formed on the substrate; forming a hard mask on the silicon-containing film; forming a pattern on the hard mask by etching the hard mask; and etching the silicon-containing film using the hard mask on which the pattern is formed, wherein the hard mask has a first film formed on the silicon-containing film and containing tungsten, and a second film formed on the first film and containing zirconium or titanium and oxygen.