High Voltage Power Improves EUV Lithography Production Line Yield

The advent of Extreme Ultraviolet (EUV) lithography marks a critical juncture in semiconductor manufacturing, enabling the patterning of features down to the sub-7-nanometer nodes and beyond. At the heart of this technological leap is the high-power, high-stability EUV light source, which fundamentally relies on sophisticated high-voltage (HV) power supply systems. These systems are not merely components but active, precision-controlled instruments that directly dictate the quality and stability of the plasma-based light generation process, making their performance a primary factor in the overall production line yield. Yield improvement in EUV is complex, encompassing defectivity reduction, critical dimension (CD) uniformity, and process window stability. The HV power supply plays a pivotal role in all three aspects by ensuring the temporal and energetic precision of the plasma excitation.

The most common method for generating EUV light involves firing highly synchronized laser pulses at microdroplets of molten tin, creating a high-temperature, high-density plasma that emits the desired 13.5 nm radiation. The HV power system is the central enabler for this high-frequency, pulsed operation. It must charge large energy storage capacitors extremely rapidly and deliver high-current pulses—often in the tens of kiloamperes range—with sub-nanosecond timing precision to the laser-produced plasma (LPP) or, in older architectures, the gas-discharge-produced plasma (DPP) electrodes. The stability of the EUV dose, which is the total energy delivered to the photoresist on the wafer, is directly proportional to the stability and repeatability of these high-voltage pulses. Any fluctuation in the pulse magnitude, shape, or timing introduces a corresponding fluctuation in the plasma temperature, the conversion efficiency of laser energy to EUV light, and consequently, the final EUV dose. Dose instability leads to critical dimension uniformity (CDU) variations across the wafer and from wafer-to-wafer, which manifests as stochastically distributed feature size errors. These errors are a major contributor to device failure and yield loss in advanced nodes. By maintaining ultra-low jitter and high pulse-to-pulse energy stability, the HV system minimizes these CDU variations, thereby directly bolstering the process window and overall production yield.

Furthermore, the longevity and health of critical EUV system components are managed by the HV power supply. In LPP sources, debris mitigation is crucial. While gas curtains and magnetic fields manage most of the debris, the plasma formation process itself must be controlled to minimize electrode erosion. The HV power supply, particularly in older DPP architectures, dictates the pre-pulse and main-pulse synchronization that controls the initial plasma formation (Z-pinch effect). Imprecise synchronization or unstable pulse characteristics can lead to excessive electrode ablation, generating metallic debris that contaminates the collection optics. The resulting mirror degradation necessitates time-consuming maintenance, reducing system uptime and throughput, which indirectly impacts yield by limiting the number of usable exposure hours. Modern HV systems are engineered with advanced pulse-shaping circuits and control algorithms to optimize the plasma conditions for maximum EUV conversion efficiency while simultaneously minimizing the parasitic energy that contributes to component wear and debris generation, thus improving the effective uptime yield of the tool.

The requirement for increasing EUV source power—driven by the industry's need for higher throughput (wafers per hour)—places an escalating demand on the HV power infrastructure. Higher source power necessitates higher laser pulse energy and a higher pulse repetition rate (up to 50 kHz). The HV system must not only handle this dramatically increased power density but also maintain the same stringent stability and precision requirements. This involves innovations in power conditioning, thermal management of the HV components, and the use of fast-switching, high-power semiconductor devices (such as advanced silicon carbide or gallium nitride-based components) to ensure the power train can sustain the high repetition rates without introducing thermal drift or instability. The successful scaling of EUV power relies entirely on the successful scaling and control of the associated HV power delivery, which is the cornerstone for achieving the necessary throughput levels for economically viable high-volume manufacturing (HVM) yield. The complexity of these systems necessitates on-board, real-time diagnostic and control loops operating in the microsecond domain, allowing the HV supply to dynamically adjust its output to compensate for plasma process variations and ensure consistent EUV delivery, thus transforming a raw power input into a highly stable and patterned energy output that maximizes lithography yield.