Halftone Phase Shift Mask Blank for ArF Laser Stability
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Solution Overview
Problem
Current halftone phase shift masks experience significant pattern size variation degradation when exposed to high-energy radiation from ArF excimer laser light, leading to reduced service lifetime and increased processing costs due to the need for complex mask patterns and miniaturization requirements.
Innovation Solution
A halftone phase shift mask blank with a halftone phase shift film composed of a silicon base material containing silicon, nitrogen, and optionally oxygen, with a minimal content of transition metals, is developed to minimize pattern size variation degradation. The film has a thickness of up to 70 nm, providing a phase shift of 150° to 200° and transmittance of 3% to 30% for exposure light, allowing for reduced refractive index and extinction coefficient while maintaining necessary optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a halftone phase shift mask uses conventional materials (MoSiO, MoSiON) for the halftone phase shift film, then the mask can provide the necessary phase shift and transmittance for pattern formation, but the mask experiences significant pattern size variation degradation when exposed to ArF excimer laser light, reducing service lifetime
Solution Approach 1:
The patent changes the material composition parameters of the halftone phase shift film by limiting transition metal content to 1 at% or less and adjusting silicon, nitrogen, and oxygen ratios. This parameter optimization reduces the refractive index and extinction coefficient, minimizing pattern size variation degradation under ArF excimer laser exposure while maintaining necessary optical properties for phase shift and transmittance
Solution Approach 2:
The patent employs a composite material approach by creating a halftone phase shift film with a specific composition of silicon base material combined with controlled amounts of nitrogen and oxygen, and minimal transition metals. This composite structure achieves both durability against laser-induced degradation and the required optical characteristics for effective photolithography
2Manufacturing precision
If the halftone phase shift film is made thinner to reduce 3D effect and improve pattern formation, then the manufacturing precision improves, but the phase shift capability and transmittance may be compromised
Solution Approach 1:
The patent optimizes the optical parameters (refractive index and extinction coefficient) through controlled material composition, enabling thinner film designs that maintain sufficient phase shift capability. By adjusting the silicon-nitrogen-oxygen ratio and limiting transition metals, the film achieves the necessary optical properties at reduced thickness, improving pattern formation accuracy while preserving phase shift function
3Manufacturing precision
If complex mask patterns are used to meet miniaturization requirements, then the manufacturing precision of circuit patterns improves, but the device complexity and processing cost increase
Solution Approach 1:
The patent optimizes the optical parameters of the halftone phase shift film to reduce pattern size variation degradation, which simplifies the overall mask design requirements. By achieving minimal degradation through material composition control, the system can use less complex mask patterns while still meeting miniaturization precision requirements, thereby reducing device complexity and processing costs
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 halftone phase shift mask exhibits minimal pattern size variation degradation upon exposure to ArF excimer laser light, extending its service lifetime and enabling accurate pattern miniaturization with reduced processing complexity and cost.
Implementation Method 1
The phase shift method is by forming a pattern of film capable of phase reversal of approximately 180 degrees on a photomask, such that contrast may be improved by utilizing optical interference
Implementation Method 2
a mask pattern of halftone phase shift film formed on the substrate, capable of providing a phase shift of approximately 180 degrees and having an insufficient transmittance to contribute to pattern formation
Data Source
Figure 1A~1B
Figure 2A~2C
AI summary
A halftone phase shift mask blank is provided comprising a transparent substrate and a halftone phase shift film which is composed of a silicon base material having a Si+N+O content of at least 90 at%, a Si content of 30-70 at%, a N+O content of 30-60 at%, and an O content of up to 30 at%, and has a thickness of up to 70 nm. The halftone phase shift film is thin enough for mask pattern processing, undergoes minimal pattern size variation degradation upon exposure to sub-200 nm radiation, and maintains a necessary phase shift and transmittance.