Key Technologies for Improving Discharge Uniformity in Excimer Laser High-Voltage Power Supplies

Excimer lasers (e.g., ArF, KrF) are indispensable deep-ultraviolet high-power pulsed sources in lithography, microprocessing, and medical applications. Their performance hinges on the discharge uniformity of high-voltage power supplies—non-uniform discharge triggers local arcing, gas degradation, electrode erosion, and energy fluctuations. This article analyzes five key dimensions for enhancing discharge uniformity: pulse modulation, synchronization control, electrode design, pre-ionization, and thermal management. 
1. Pulse Front Modulation Optimization
Traditional thyratron switches exhibit pulse fronts exceeding 100 ns, leading to discharge channel contraction and uneven energy deposition. All-solid-state magnetic pulse compression (MPC) compresses the pulse front to 50–100 ns, achieving dual benefits: 
• Reduced Impedance Fluctuations: Fast voltage rise shortens the delay between pre-ionization and main discharge, suppressing local arcs; 
• Improved Energy Conversion: Minimized thermal loss enhances electrical-to-laser radiation efficiency, while reduced halogen gas consumption extends gas lifetime. 
2. Dual-Cavity Discharge Synchronization
Synchronization within ±5 ns is critical for dual-cavity excimer lasers (Master Oscillator MO and Power Amplifier PA): 
• Closed-Loop Control: Delay measurement units acquire real-time discharge signals, and a main controller dynamically adjusts output delays based on temperature and pressure data, countering timing jitter; 
• Programmable Delay Modules: With 0.25 ns resolution and fixed-delay calibration for system errors (100–300 ns), stable synchronization at 4 kHz repetition rates is achieved. 
3. Electrode Structural Innovations
Electric field distribution on electrode surfaces is pivotal: 
• Micro-protrusions/Depressions: Grid or dot arrays (diameter: 10 μm–1 mm, height: 1 μm–3 mm) induce uniform filamentary discharge. For example, dot protrusions increase discharge channels by 60%, reducing single-channel energy and localized erosion; 
• Anode-Cavity Matching: Paired needle-cavity electrodes with matched curvature homogenize electric fields, expanding the stable glow discharge range by 3.2 kV and suppressing sparks. 
4. Pre-Ionization and Gas Flow Control
• Dual-Discharge Technology: A pre-ionization electrode near the cathode generates a uniform ionization layer via corona discharge, lowering ignition voltage and preventing random discharges; 
• Active Gas Cooling: High-speed airflow (102 m/s) dissipates heat, inhibiting local gas expansion and field distortion. Experiments show airflow increases the glow-to-spark threshold current by 2.1×, extending stable operation. 
5. Thermal Management and Intelligent Control
Thermal effects increase conductivity and discharge non-uniformity: 
• Multi-Objective Optimization: Separating energy stability (overshoot/non-overshoot) and dose accuracy control, genetic algorithms solve: 
  F=w_1HV_{Em,i} + w_2HV_{Dm,i} w_3HV_{Te} 
  where HV_{Te} is the temperature compensation term. Weight coefficients (w_1+w_2+w_3=1) balance voltage range and thermal effects; 
• Distributed Thermal Monitoring: Sensors at key nodes trigger cooling systems (e.g., fan speed adjustment) to stabilize gas density (N), preventing increased reduced field (E/N). 
Conclusion
Improving discharge uniformity requires multi-technology synergy: pulse front modulation lays the foundation; electrode and pre-ionization designs optimize field distribution; synchronization and airflow mitigate external disturbances; and intelligent algorithms enable dynamic balance. Future directions include high-precision semiconductor switches (replacing thyratrons), multi-physics coupling simulations (electro-thermal-fluid), and adaptive learning control (e.g., reinforcement learning replacing PI algorithms), meeting extreme demands for laser stability and lifetime in semiconductor lithography.