Halftone Phase Shift Mask Film Composition for ArF Lithography
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Solution Overview
Problem
Current halftone phase shift masks experience significant pattern size variation degradation and chemical damage when exposed to high-energy ArF excimer laser light, leading to reduced service lifetime and accuracy in semiconductor lithography.
Innovation Solution
A halftone phase shift mask blank with a halftone phase shift film composed of a silicon base material containing a transition metal, such as molybdenum, with a transition metal content up to 3 at%, and a total content of silicon, nitrogen, and oxygen of at least 90 at%, providing improved chemical resistance and processability while minimizing pattern size variation degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a halftone phase shift mask with traditional materials (MoSiO or MoSiON) is used, then the mask can provide the required phase shift and transmittance for pattern formation, but the mask experiences significant pattern size variation degradation and chemical damage when exposed to high-energy ArF excimer laser light, reducing service lifetime
Solution Approach 1:
The patent changes the compositional parameters of the halftone phase shift film by incorporating specific amounts of carbon (0.1-10 at%) and controlling oxygen content (1-30 at%), along with silicon (40-60 at%) and transition metal (1-10 at%). This compositional modification reduces pattern size variation degradation and improves resistance to ArF excimer laser light damage while maintaining the required optical properties for phase shift and transmittance
Solution Approach 2:
The patent creates a composite material system by combining silicon, transition metal (such as molybdenum), oxygen, and carbon in specific proportions. This composite halftone phase shift film integrates multiple elements to achieve synergistic effects: silicon provides the base structure, transition metal enables phase shift functionality, oxygen controls stoichiometry, and carbon reduces laser-induced damage and pattern size variation, thereby extending service lifetime
2Manufacturing precision
If the transition metal content in the halftone phase shift film is increased to improve phase shift capability, then the phase shift effect is enhanced, but the chemical resistance and etching performance deteriorate
Solution Approach 1:
The patent optimizes the transition metal content to a specific range (1-10 at%, preferably 3-7 at%) rather than using high concentrations. This parameter control ensures sufficient phase shift capability while preventing excessive transition metal from causing chemical instability and poor etching performance. The balanced composition maintains manufacturing precision without sacrificing ease of manufacture
3Measurement precision
If the mask is cleaned frequently to remove haze and foreign matter, then the visibility and pattern quality are improved, but the cumulative irradiation energy damage and pattern size variation increase
Solution Approach 1:
The patent incorporates carbon into the halftone phase shift film composition, which specifically addresses the haze formation problem caused by ArF excimer laser irradiation. The carbon-containing film structure reduces the formation of ammonium sulfate crystals and organic matter accumulation that cause haze, allowing the mask to maintain pattern quality over extended periods without frequent cleaning, thereby preserving mask durability
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 halftone phase shift mask exhibits minimal pattern size variation degradation and enhanced chemical resistance, maintaining accuracy and extending the service lifetime even with increased cumulative irradiation energy, and offers improved etching rates during fluorine-based dry etching.
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 halftone phase shift film formed thereon having a phase shift of 150° to 200° and a transmittance of 3 % to 30 % with respect to light of wavelength up to 200 nm
Data Source
Figure 1A~1B
Figure 2A~2C
AI summary
A halftone phase shift mask blank (100) comprising a transparent substrate (10) and a halftone phase shift film (1) thereon is provided. The halftone phase shift film includes at least one layer composed of a silicon base material having a transition metal content ≤ 3 at%, a Si+N+O content ≥ 90 at%, a Si content of 30-70 at%, a N+O content of 30-60 at%, and an O content ≤ 30 at%, and having a sheet resistance ≤ 1013 /Ω/□. The halftone phase shift film undergoes minimal pattern size variation degradation upon exposure to sub-200 nm radiation, and has chemical resistance and improved processability.