Low-Noise Driving Technology for Electron Beam High-Voltage Power Supply

Electron beam equipment is extremely sensitive to power supply noise. The switching noise (frequency 20kHz-1MHz) and electromagnetic interference (EMI) of the high-voltage power supply will be superimposed on the output voltage, leading to electron beam deflection error (exceeding 1μm) and reduced focusing accuracy (line width deviation exceeding 2nm). Especially in high-precision applications such as electron beam lithography (EBL), noise problems directly restrict device yield. The traditional driving technology adopts hard-switching topology, which has large switching losses and noise peaks exceeding 500mV. Although the noise is suppressed by adding filter circuits, the power supply volume increases by 30%, and high-frequency noise cannot be completely eliminated.
The low-noise driving technology needs to make breakthroughs in three aspects: "topology optimization, filter design, and wiring shielding": at the topology optimization level, the phase-shifted full-bridge soft-switching topology is adopted. By controlling the conduction sequence of the switching tubes, the switching action is carried out under zero voltage (ZVS) or zero current (ZCS) state, reducing switching losses by 70% and noise source intensity by 40%. At the same time, synchronous rectification technology is introduced to reduce the forward voltage drop of the rectifier tube and further reduce the output ripple (from 300mV to 50mV); at the filter design level, a combined filter circuit of "LC + EMI" is adopted. The LC filter uses low-ESR capacitors (equivalent series resistance <10mΩ) and high-permeability inductors (cores made of nanocrystalline materials) to suppress low-frequency noise (20kHz-100kHz). The EMI filter adopts a differential-mode + common-mode dual filtering structure with insertion loss >60dB to suppress high-frequency noise (100kHz-1MHz); at the wiring shielding level, the high-voltage cables adopt a double-layer shielding structure (inner aluminum foil, outer copper mesh) with shielding effectiveness >80dB to avoid external interference coupling. The control circuit board adopts a "star grounding" design to reduce ground loop noise, and the layout distance between power devices and control chips is >5cm to reduce electromagnetic radiation coupling.
After applying this technology in an electron beam lithography equipment, the power supply output noise decreased from 520mV to 45mV, the electron beam deflection error decreased from 1.2μm to 0.3μm, the lithography line width deviation decreased from 2.5nm to 0.8nm, and the device yield increased from 82% to 95%. At the same time, the power supply volume was reduced by 25%, meeting the miniaturization needs of the equipment.