Stacked Hard Mask Film for Mask Blanks With Faster Etching
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Solution Overview
Problem
Conventional mask blanks with Si-based hard mask films suffer from insufficient pattern resolution, in-plane CD uniformity, and CD linearity due to poor adhesiveness between the resist film and the hard mask film, and a slow etching rate of tantalum-based hard mask films.
Innovation Solution
A mask blank with a stacked hard mask film structure, where the lower layer is formed of silicon and oxygen, and the upper layer is formed of tantalum and oxygen with an oxygen content of 30atom% or more, and a ratio of the upper layer thickness to the total hard mask film thickness of 0.7 or less, is used to enhance pattern resolution and etching rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a Si-based hard mask film is used, then the etching rate is maintained, but the pattern resolution and CD uniformity are insufficient
Solution Approach 1:
The patent applies composite materials by creating a stacked hard mask film structure where a Ta-based material layer (providing high resist adhesiveness and pattern resolution) is combined with a Si-based material layer (providing fast etching rate). This composite structure allows both materials to work together, achieving high pattern resolution while maintaining sufficient etching rate, thereby resolving the technical contradiction between these two parameters.
Solution Approach 2:
The patent applies local quality by assigning different functional properties to different layers of the hard mask film. The Ta-based material layer (upper layer with thickness ratio 0.2-0.7) provides local high adhesiveness for the resist film and excellent pattern resolution, while the Si-based material layer (lower layer) provides local fast etching rate. This localized functional differentiation resolves the contradiction by allowing each layer to optimize for its specific function.
2Manufacturing precision
If a Ta-based hard mask film is used, then the pattern resolution and adhesiveness are improved, but the etching rate decreases
Solution Approach 1:
The patent uses composite materials to combine Ta-based material (providing high CD uniformity and resist adhesiveness) with Si-based material (providing fast etching rate). The stacked structure allows the Ta-based layer to dominate the resist interaction and pattern formation, achieving high CD uniformity, while the Si-based layer contributes to the overall etching rate, preventing it from becoming too slow.
Solution Approach 2:
The patent applies local quality by making the Ta-based material the upper layer with controlled thickness ratio (0.2-0.7), positioning it where it directly interacts with the resist film to provide local high adhesiveness and CD uniformity. The Si-based material forms the lower layer, providing local fast etching capability. This spatial differentiation of properties resolves the contradiction between CD uniformity and etching rate.
3Reliability
If silylation processing is applied to Si-based hard mask film, then the resist adhesiveness is improved, but the pattern resolution and CD linearity remain insufficient
Solution Approach 1:
The patent applies inversion by reversing the conventional approach: instead of treating a Si-based film to improve adhesiveness (which only partially works), the patent uses a Ta-based material layer as the primary adhesiveness-providing layer. The Ta-based material inherently provides superior resist adhesiveness without requiring silylation processing, and this inversion approach simultaneously achieves excellent CD linearity, overcoming the limitations of the conventional Si-based approach.
Data Source
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AI summary
[PROBLEM TO BE SOLVED] Provided is a mask blank that can prevent reduction of an etching rate of an entire hard mask film while enhancing pattern resolution, in-plane CD uniformity, and CD linearity. [MEANS FOR SOLVING THE PROBLEM] The mask blank has a structure where a thin film for pattern formation and a hard mask film are stacked in this order on a transparent substrate, featured in that the thin film is formed of a material containing chromium, the hard mask film includes a stacked structure of a lower layer and an upper layer, the lower layer is formed of a material containing silicon and oxygen, the upper layer is formed of a material containing tantalum and oxygen with an oxygen content of 30atom% or more, and the ratio of a thickness of the upper layer relative to a total thickness of the hard mask film is 0.7 or less.