230nm Filter Application Selection Guide
1. Deep UV Sterilization Systems
Application Scenario
In air purification or water treatment devices designed for human-coexistence environments, 230nm deep UV light efficiently disrupts microbial DNA (e.g., viruses, bacteria) while minimizing harm to human skin and eyes. For example, dynamic disinfection equipment in public spaces requires precise 230nm light output while blocking harmful UV radiation above 230nm (e.g., 236nm, 257nm).
Filter Configuration Requirements
a. Spectral Characteristics
- Central Wavelength: 230±1nm, ensuring matching with the main emission peak of deep UV light sources (e.g., KrCl excimer lamps).
- Bandwidth: 10nm (FWHM). A narrow bandwidth minimizes stray light interference, significantly enhancing sterilization efficiency by focusing energy on the optimal germicidal wavelength.
- Cutoff Range: Transmittance < 0.01% (OD ≥ 6) in 235–265nm. This high cutoff depth effectively blocks long-wave UV radiation, eliminating potential risks of skin irritation or eye damage from secondary peaks like 236nm.
b. Material & Coating Technology
- Substrate: JGS2-grade quartz glass, providing >80% transmittance in 200–230nm with excellent resistance to high temperatures and chemical corrosion.
- Coating Process: 26-layer thin-film structure using alternating HfO₂ (high refractive index) and SiO₂ (low refractive index), deposited via Ion Beam Assisted Deposition (IAD). This ensures high compactness and stability, limiting long-term central wavelength drift to <1nm.
c. Environmental Adaptability
- Humidity Resistance: Transmittance fluctuation <0.5% under >90% humidity, preventing wavelength shift caused by water vapor adsorption.
- Irradiation Tolerance: High laser damage threshold (>1J/cm²) for the coating, ensuring durability under continuous deep UV exposure.
Selection Rationale & Problem Solving
- Precision Sterilization: The 10nm narrowband design ensures only the 230nm germicidal wavelength acts on microorganisms, avoiding collateral damage from broad-spectrum UV. For instance, unfiltered 236nm secondary peaks from KrCl lamps could otherwise cause skin erythema.
- Safety Assurance: The strict cutoff in 235–265nm (OD ≥ 6) reduces harmful radiation doses to below safety thresholds, enabling safe human-coexistence disinfection.
- Reliability Enhancement: Quartz substrates and IAD hard coatings maintain performance across extreme temperatures (-20 to 150°C) and high humidity, ideal for harsh operational environments.
2. Semiconductor Lithography Processes
Application Scenario
In semiconductor manufacturing, 230nm deep UV light is used for specialized lithography (e.g., etching of silicon photonic devices), requiring strict wavelength precision and uniformity to improve resolution and reduce defects. For example, silicon waveguide etching demands precise 230nm light control to avoid edge roughness that could degrade device performance.
Filter Configuration Requirements
a. Spectral Characteristics
- Central Wavelength: 230±0.5nm, meeting the ultra-tight wavelength control requirements of lithography systems (e.g., ±0.1% tolerance).
- Bandwidth: 5nm (FWHM). This ultra-narrow bandwidth minimizes chromatic dispersion, enhancing the sharpness of lithographic pattern edges critical for sub-micron feature sizes.
- Transition Region Steepness: Transition width from 90% transmittance to OD3 <3.6nm. This suppresses incoherent light interference, ensuring high contrast in lithographic patterns.
b. Material & Coating Technology
- Substrate: Fused silica or CaF₂ crystals, offering >90% transmittance at 230nm with extremely low thermal expansion coefficients (<1×10⁻⁶/°C) to minimize wavelength drift from temperature fluctuations.
- Coating Process: All-dielectric multi-layers (e.g., Al₂O₃/AlF₃) deposited via Ion Beam Sputtering (IBS), achieving nanometer-level thickness control (±1nm) for consistent bandwidth and central wavelength across batches.
c. Environmental Adaptability
- Thermal Stability: Central wavelength drift <0.5nm in high-temperature lithography environments (80–120°C), eliminating registration errors caused by thermal expansion.
- Contamination Resistance: TiO₂ photocatalytic surface coating reduces adhesion of photoresist splatter and particulates, maintaining long-term transmittance stability in cleanroom environments.
Selection Rationale & Problem Solving
- Resolution Improvement: The 5nm narrowband and steep transition design enable sub-micron lithography resolution, essential for advanced silicon photonics manufacturing. For example, precise 230nm etching directly impacts the optical performance of waveguide structures in photonic chips.
- Process Consistency: Low-expansion substrates and IBS coating precision limit wavelength drift to ±0.5nm, reducing overlay errors and improving wafer yield in multi-layer lithography.
- Environmental Durability: High-temperature-resistant coatings and self-cleaning surfaces adapt to the high-radiation, high-particle environments of lithography tools, minimizing maintenance downtime and costs.
3. Selection Decision Guidelines
a. Sterilization Applications:
Prioritize strict cutoff in 235–265nm (OD ≥ 6) and corrosion-resistant materials to ensure safety and long-term reliability.
b. Lithography Applications:
Focus on ultra-precise wavelength control (±0.5nm) and thermal stability, paired with low-expansion substrates and high-accuracy coating processes.
c. General Principle:
Opt for hard-coating technologies (IAD/IBS) across applications to enhance mechanical strength and environmental resilience, ensuring consistent performance under demanding conditions.
