Transfer Mask Blank Structure for Precise Fine-Pattern Etching
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Solution Overview
Problem
The chromium compound in existing hard mask films etches isotropically with oxygen-containing chlorine-based gases, leading to increased opening widths of patterns formed on the mask, which hinders miniaturization and high integration in semiconductor devices.
Innovation Solution
A mask blank structure with a pattern-forming thin film, a first hard mask film containing chromium, and a second hard mask film containing tantalum, where the tantalum is unsaturated with oxygen, is used. This configuration allows for controlled etching and pattern formation with reduced side wall recession.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a chromium compound hard mask film is used for pattern formation, then the etching process can be performed with oxygen-containing chlorine-based gas, but the chromium compound etches isotropically causing side wall recession and increased opening width
Solution Approach 1:
The patent divides the hard mask film into two distinct layers: a first hard mask film containing chromium compound for etching resistance, and a second hard mask film containing tantalum compound for dimensional stability. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between etching processability and pattern precision.
Solution Approach 2:
The patent employs a composite hard mask structure combining chromium-based materials and tantalum-based materials. The chromium compound provides excellent etching resistance against oxygen-containing chlorine-based gas, while the tantalum compound with oxygen unsaturation prevents isotropic etching and maintains vertical side walls, achieving both ease of manufacture and manufacturing precision.
2Reliability
If over-etching is performed to achieve vertical side walls, then the etching completeness is improved, but the opening width of the pattern increases due to isotropic etching of chromium compound
Solution Approach 1:
The second hard mask film containing tantalum compound acts as an intermediary layer between the first hard mask film and the pattern-forming thin film. This intermediary layer with oxygen unsaturation prevents the isotropic etching that would otherwise occur in the chromium-based first hard mask film, allowing over-etching to proceed while maintaining precise opening width control through the protective effect of the tantalum compound.
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 mask blank structure enables the formation of fine patterns on pattern-forming thin films, facilitating miniaturization and high integration in semiconductor devices by maintaining precise pattern dimensions during etching.
Implementation Method 1
wherein the second hard mask film contains tantalum and swells in an oxygen-containing gas atmosphere
Implementation Method 2
the chromium compound constituting the hard mask film (etching mask film) is etched isotropically with respect to the oxygen-containing chlorine-based gas
Data Source
AI summary
Provided is a mask blank having a structure in which a pattern-forming thin film, a first hard mask film, and a second hard mask film are stacked in this order on a main surface of a substrate. The pattern-forming thin film contains at least one element selected from silicon and transition metals. The first hard mask film contains chromium. The second hard mask film contains tantalum. The tantalum of the second hard mask film contains tantalum that is unsaturated with oxygen. The thickness of the pattern-forming thin film is 20 nm or more. The thickness of the first hard mask film is 15 nm or less. The thickness of the second hard mask film is 10 nm or less.