Multilayer Phase Shift Film for ArF Lithography
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Solution Overview
Problem
Phase shift films used in semiconductor manufacturing, particularly with ArF excimer lasers, face challenges in achieving high transmittance and maintaining etching selectivity and repair rates, with existing single-layer silicon nitride films offering low transmittance and two-layer structures risking pattern wall level differences during dry etching.
Innovation Solution
A phase shift film with a multilayer structure comprising multiple sets of stacked low and high transmission layers, where the low transmission layer is made of silicon and nitrogen with high nitrogen content and the high transmission layer is made of silicon and oxygen with high oxygen content, optimized for ArF excimer laser exposure, ensuring transmittance of 20% or more and precise pattern formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-layer silicon nitride phase shift film is used, then the structure is simple and easy to manufacture, but the transmittance to ArF exposure light is low (only approximately 18%)
Solution Approach 1:
The phase shift film is divided into multiple layers with different functions: a first phase shift film (silicon nitride) for phase difference and a second phase shift film (silicon oxide) for transmittance enhancement. This segmentation allows each layer to optimize its specific function rather than requiring a single layer to achieve all properties.
Solution Approach 2:
The invention uses a composite structure combining silicon nitride and silicon oxide materials in a multilayer configuration. This composite approach leverages the high phase difference capability of silicon nitride and the high transmittance of silicon oxide to achieve overall transmittance of 20% or more while maintaining necessary phase differences.
2Illumination intensity
If oxygen is incorporated into silicon nitride to increase transmittance, then the transmittance increases, but the etching selectivity for silicon oxide substrate decreases
Solution Approach 1:
The phase shift film is segmented into distinct layers: one layer optimized for phase difference (silicon nitride) and another layer optimized for transmittance (silicon oxide). This segmentation allows each layer to have optimized composition and properties without compromising the other functions, solving the etching selectivity problem while maintaining high transmittance.
Solution Approach 2:
Different regions of the phase shift film structure have different material compositions tailored to specific local functions. The silicon nitride layer provides high phase difference with appropriate etching selectivity, while the silicon oxide layer provides high transmittance. Each layer's composition is locally optimized for its specific role in the overall system.
3Illumination intensity
If a two-layer structure with silicon nitride and silicon oxide is used to achieve high transmittance, then the transmittance increases to 20% or more, but the thickness of each layer becomes large causing level difference in pattern side wall
Solution Approach 1:
The phase shift film is divided into multiple thin layers rather than using thick single layers. This segmentation into first and second phase shift films with controlled individual thicknesses allows the total optical path difference to be achieved while keeping each layer thin, thereby minimizing level differences in pattern side walls during dry etching.
Solution Approach 2:
The invention transitions from a single-layer approach to a multilayer approach, adding the dimension of layering to solve the problem. By distributing the required optical path difference across multiple layers with optimized individual thicknesses, the system achieves high transmittance while controlling the thickness of each individual layer to minimize side wall level differences.
4Illumination intensity
If a multilayer structure with multiple sets of stacked low and high transmission layers is used, then the transmittance and phase difference are enhanced, but the device complexity increases
Solution Approach 1:
The phase shift film is segmented into a first phase shift film and a second phase shift film with distinct material compositions and functions. This segmentation into two main layers provides the necessary transmittance and phase difference enhancement without creating excessive complexity, balancing performance improvement with manufacturing feasibility.
Solution Approach 2:
The invention optimizes specific parameters such as the thickness and material composition of each layer to achieve the desired optical properties. By carefully controlling the thickness of the first and second phase shift films and their respective nitrogen and oxygen contents, the system achieves enhanced transmittance and phase difference while maintaining a manageable structural complexity suitable for manufacturing.
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 multilayer structure enhances transmittance and phase difference, improving pattern contrast and transfer accuracy while minimizing pattern wall level differences, thus addressing the limitations of single-layer and two-layer films.
Implementation Method 1
a phase shift film having a transmittance of 20% or more to exposure light of an ArF excimer laser
Implementation Method 2
the phase shift film includes a structure having two or more sets of a stacked structure, each set including a low transmission layer and a high transmission layer
Data Source
AI summary
Provided is a mask blank including a phase shift film having a transmittance of 20% or more difficult to achieve in a phase shift film of a single layer made of a silicon nitride material, and the phase shift film is achieved by using a structure having two or more sets of a stacked structure, each set including a low transmission layer and a high transmission layer disposed in order from a transparent substrate side.The mask blank includes a phase shift film on a transparent substrate. The phase shift film has a function of transmitting exposure light of an ArF excimer laser at a transmittance of 20% or more. The mask blank has two or more sets of a stacked structure, each set including a low transmission layer and a high transmission layer. The low transmission layer is formed of a silicon nitride-based material. The high transmission layer is formed of a silicon oxide-based material. The high transmission layer provided at an uppermost position is thicker than the high transmission layer provided at a position other than the uppermost position. The low transmission layer is thicker than the high transmission layer provided at a position other than the uppermost position.