High-Voltage Power Supply Stabilization Technology for Electron Beam Lithography Systems

Electron beam lithography systems, as core equipment for nanoscale pattern fabrication, rely critically on the stability of their high-voltage power supplies. The power supply provides acceleration voltage (typically 20–30 kV) to the electron gun, where even minor fluctuations (e.g., 0.001%) can deflect the electron beam trajectory, causing pattern distortion. For instance, a 100 ppm fluctuation in a 30 kV supply may induce micrometer-level errors in the scanning field. Thus, high-precision voltage stabilization technology is foundational to the system’s accuracy. 
1. Core Technology: Dual-Loop Regulation and Hybrid Compensation
• Dual-Loop System: 
  • Direct Adjustment Loop: A power transistor in the high-voltage circuit dynamically adjusts its voltage drop to compensate for output variations. This loop comprises a high-voltage divider, high-gain comparator (gain ≥10⁵), compensation network, and regulator, achieving microsecond response to load transients. 
  • Indirect Adjustment Loop: A low-side inverter (e.g., 5 kHz sinusoidal oscillator) is regulated to pre-stabilize the DC output. For example, a 700V DC is converted to a 320V sinusoidal wave, then multiplied to 30 kV via a rectifier cascade. This reduces the regulator’s voltage drop, extending component life and minimizing thermal drift. 
• Centralized and Decentralized Compensation: 
  • Centralized compensation uses a PID amplifier (transfer function G(s) \approx \frac{(T_1s+1)(T_2s+1)}{T_0s}) to optimize dynamics; decentralized compensation employs independent RC networks for each loop, resolving stability issues under high gain while maintaining static accuracy (line regulation ≤2×10⁻⁵). 
2. Ripple Suppression and Noise Immunity
• Low-Ripple Inverter: A 5 kHz sinusoidal oscillator replaces conventional saturating inverters, eliminating spike noise and suppressing output ripple to ≤5×10⁻⁶ (peak-to-peak). 
• Power-Frequency Interference Cancellation: 
  • AC Balancer: Generates phase/amplitude-tunable 50 Hz signals injected inversely at the output to cancel power-frequency ripple (≥40 dB attenuation). 
  • Dual-Channel Amplifier: Separates DC (high-gain op-amp) and AC (wide-bandwidth op-amp) paths, balancing low-frequency precision and high-frequency noise rejection. 
3. Stability Enhancement Measures
• Reference and Sampling System: 
  • The reference voltage (e.g., 10V REF-grade) features temperature compensation (≤2.5 ppm/℃) and electromagnetic shielding in a thermal chamber (±0.2℃), ensuring long-term stability (0.001%/8 hours). 
  • High-voltage dividers use precision wire-wound resistors (RX70, 0.01% tolerance), with high-arm resistors oil-cooled and low-arm resistors thermally stabilized, achieving drift <10 ppm. 
• Pre-Regulation and Isolation: 
  • Input AC is pre-stabilized via a voltage-regulating transformer (line regulation ≤1%) to suppress grid noise; five independent DC auxiliary supplies power critical circuits, with ripple ≤1 mV and temperature coefficient ≤5×10⁻⁵/℃. 
4. Performance Metrics and Evolution
Key specifications for a 30 kV power supply: 
• Static Accuracy: Line regulation ≤3.5×10⁻⁶ (±10% input), load regulation ≤4×10⁻⁶ (100 μA step). 
• Long-Term Stability: Drift ≤4×10⁻⁵/4 hours, temperature coefficient ≤5 ppm/℃. 
• Application Impact: In a 4 mm×4 mm scanning field, displacement error due to voltage fluctuation is limited to 0.01 μm, increasing pattern yield by >30%. 
Conclusion
The stabilization technology for electron beam lithography power supplies, combining dual-loop control, hybrid compensation, and multi-stage noise suppression, achieves ppm-level static accuracy and millisecond dynamic response. Future advancements in resonant switching and digital adaptive compensation will further enhance integration and intelligence, enabling next-generation sub-nanoscale lithography.