Argon fluoride laser

The argon fluoride laser (ArF laser) is a particular type of excimer laser, which is sometimes (more correctly) called an exciplex laser. With its 193-nanometer wavelength, it is a deep ultraviolet laser, which is commonly used in the production of semiconductor integrated circuits, eye surgery, micromachining, and scientific research. "Excimer" is short for "excited dimer", while "exciplex" is short for "excited complex". An excimer laser typically uses a mixture of a noble gas (argon, krypton, or xenon) and a halogen gas (fluorine or chlorine), which under suitable conditions of electrical stimulation and high pressure, emits coherent stimulated radiation (laser light) in the ultraviolet range.

ArF (and KrF) excimer lasers are widely used in high-resolution photolithography machines, one of the critical technologies required for microelectronic chip manufacturing. Excimer laser lithography has enabled transistor feature sizes to shrink from 800 nanometers in 1990 to 22 nanometers in 2012.

An argon fluoride laser absorbs energy from a source, causing the argon gas to react with the fluorine gas producing argon monofluoride, a temporary complex, in an excited energy state:

The complex can undergo spontaneous or stimulated emission, reducing its energy state to a metastable, but highly repulsive ground state. The ground state complex quickly dissociates into unbound atoms:

The result is an exciplex laser that radiates energy at 193 nm, which lies in the far ultraviolet portion of the spectrum, corresponding with the energy difference of 6.4 electron volts between the ground state and the excited state of the complex.

The most widespread industrial application of ArF excimer lasers has been in deep-ultraviolet photolithography for the manufacturing of microelectronic devices (i.e., semiconductor integrated circuits or “chips”). From the early 1960s through the mid-1980s, Hg-Xe lamps had been used for lithography at 436, 405 and 365 nm wavelengths. However, with the semiconductor industry’s need for both finer resolution (for denser and faster chips) and higher production throughput (for lower costs), the lamp-based lithography tools were no longer able to meet the industry’s requirements.

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