EXCITATION LASER SYSTEM, METHOD OF OPERATING EXCITATION LASER SYSTEM, AND EXTREME ULTRAVIOLET PHOTOLITHOGRAPY APPARATUS INCLUDING EXCITATION LASER SYSTEM

Smart overview of the Invention

The patent describes a method and apparatus for operating an excitation laser system, crucial for extreme ultraviolet (EUV) photolithography used in semiconductor manufacturing. The system involves measuring the operating power of a laser beam and determining if it falls below a threshold. If so, the spectrum of light emitted from the laser's gain medium is optically measured to ascertain its composition, which is then adjusted accordingly. This ensures consistent laser performance, critical for the precision required in photolithography processes.

Components and Functionality

The apparatus includes an optical emission spectrum meter and a gas supply unit. The spectrum meter captures light emitted from the laser's gain medium, analyzing its composition. Based on this analysis, the gas supply unit adjusts the gas composition within the gain medium. This adjustment helps maintain the laser's power and performance, addressing issues related to power degradation over time, which can affect the photolithography process.

Application in EUV Photolithography

EUV photolithography is a technique that uses laser-generated ultraviolet light to create smaller, more compact semiconductor devices. The described laser system is part of an EUV lithography apparatus, which includes an EUV radiation source and an exposure device. The system is designed to expose a photoresist layer, sensitive to EUV light, using radiation generated by laser-produced plasma. This process is essential for creating intricate patterns on semiconductor wafers.

Detailed Mechanism

The EUV lithography apparatus utilizes reflective optic components to guide EUV light onto a mask, creating a patterned beam projected onto a photoresist-coated substrate. The mask often includes a reflective multilayered stack, enhancing the precision of the pattern. The excitation laser system plays a pivotal role in generating the EUV light by using a combination of pre-heat and main laser beams to optimize light emission from target droplets.

Technical Specifications

The excitation laser system employs a CO2 laser source, emitting infrared light at specific wavelengths. The laser beam is guided and focused to interact with target droplets, which are typically made of materials like tin or lithium. These droplets are ejected at high frequencies, and the laser pulses are synchronized with this ejection to maximize EUV light production. The system's design ensures that the laser's power, frequency, and spot size are optimized for efficient and precise photolithography.