Corrosion Protection of Electrodes in Excimer Laser High-Voltage Power Supplies: Material Challenges and Technological Innovations

Excimer laser high-voltage power supplies are core components of high-end equipment such as deep-UV lithography and precision material processing. Their electrodes face complex corrosion issues during high-voltage discharge, which degrade conductivity and thermal stability, cause gas contamination, and ultimately lead to system failure. Effective corrosion protection strategies must therefore integrate materials science, electrochemistry, and engineering design. 
I. Mechanisms and Specificity of Electrode Corrosion
1. Electrochemical Corrosion 
   High-voltage discharge ionizes gases (e.g., halogens), creating an electrolytic environment on electrode surfaces. This triggers galvanic effects, accelerating pitting and intergranular corrosion, especially under high humidity or ion contamination. 
2. Thermal Stress Corrosion 
   Pulsed discharge (at kHz-level frequencies) causes rapid temperature fluctuations, inducing thermal fatigue cracks. These cracks adsorb corrosive media (e.g., fluorides), accelerating stress corrosion cracking (SCC). 
3. Gas Erosion 
   Halogen gases (e.g., fluorine in ArF lasers) react with metal electrodes to form volatile fluorides, leading to surface spalling. For example, aluminum electrodes generate porous AlF₃, degrading conductivity. 
II. Material Selection and Design Strategies
1. Substrate Material Optimization 
   • High-Corrosion-Resistance Alloys: Chromium-zirconium copper (e.g., C18400) forms dense oxide layers (Cr: 0.5%-1.2%, Zr: 0.1%-0.3%), balancing conductivity (≥80% IACS) and halogen resistance. 
   • Refractory Metals: Tungsten and molybdenum alloys tolerate high temperatures (＞3400°C) but require coatings for oxidation resistance. 
2. Surface Reinforcement Technologies 
   • Non-Metallic Coatings: 
     ◦ Oxide Ceramics (e.g., Al₂O₃, Cr₂O₃) deposited via plasma spraying isolate corrosive media and withstand 1500°C. 
     ◦ Diamond-Like Carbon (DLC) Films reduce friction and arc erosion, tripling electrode lifespan. 
   • Metallic Platings: 
     ◦ Titanium coatings form passive films via cathodic sputtering, outperforming pure copper in halogen environments. 
   • Chemical Conversion Films: 
     ◦ Micro-Arc Oxidation grows in-situ ceramic layers on aluminum electrodes (hardness >1500 HV), sealing microcracks. 
3. Structural Innovations 
   • Embedded Electrodes: Tungsten or molybdenum inserts in copper bases disperse thermal stress and reduce localized melting. 
   • Functionally Graded Materials (FGMs): Gradual composition transitions (e.g., Cu→CuCr→Cr₂O₃) mitigate interfacial thermal mismatch. 
III. Application and Efficacy Evaluation of Protection Technologies
1. Surface Treatment Technologies 
   • Laser Surface Alloying: Short-pulse laser melting of nickel-based alloys refines grains and forms amorphous layers, reducing pitting susceptibility. 
2. Environmental Control Technologies 
   • Vapor Corrosion Inhibitors (VCIs): Amine-based compounds adsorbed on electrode surfaces block reaction paths without contaminating optics. 
   • Gas Purification: Removing water and oxygen (dew point < -70°C) reduces corrosion rates by 90%. 
3. Electrochemical Protection 
   • Cathodic Protection: Applying negative potentials to auxiliary electrodes suppresses anode dissolution but requires avoiding excessive hydrogen evolution. 
IV. Comprehensive Protection in Practical Applications
• Multi-Technology Synergy: A 6 kHz excimer laser system combining chromium-zirconium copper + micro-arc oxidation coating + VCI injection extended electrode lifespan from 500 to 3,000 hours. 
• Online Monitoring and Smart Maintenance: Real-time resistance feedback and corrosion prediction models (e.g., Arrhenius-EDA algorithms) dynamically adjust protection parameters. 
• Cost-Benefit Balance: Surface treatments account for 15%-30% of part costs but reduce downtime, improving overall efficiency by 40%. 
Conclusion
Corrosion protection for excimer laser electrodes requires advancements in material optimization, surface engineering, and system environment control. Future directions include self-healing smart coatings, high-temperature polymer composites, and digital-twin-based corrosion management platforms. Only through interdisciplinary collaboration can high-end equipment achieve reliability and longevity under extreme conditions.