In-Situ Tin Halide Quantification for Extreme Ultraviolet Light Sources in Semiconductor Lithography

October 29, 2021
Martin Mason

As process geometries continue to shrink, Extreme Ultraviolet (EUV) lithography is increasingly being deployed. The 13.5 nm wavelength EUV light is created by vaporizing droplets of molten tin with a carbon dioxide laser, creating a plasma.

A by-product of the light source creation is tin debris on the EUV light source reflective optics, which focuses the EUV light emitting from the plasma. A deposited tin thickness of around 1 nm (only several atomic layers) reduces the collector mirror reflectivity by as much as 10%, which reduces lithography throughput.

Hydrogen plasma (combined with a magnetic field) can be used to chemically remove tin in the form of stannane gas (SnH4), then efficiently exhaust it from the vacuum chamber, and prevent any further tin redeposition.

To make this tin clearing as time-efficient as possible, Aston can provide fast, actionable, accurate data from in-situ measurement, which enables the endpoint of the process to be accurately determined. This reduces the consumption of high purity hydrogen, and cuts the overall tin clearing time needed – freeing up more time on the expensive lithography tools.

Learn more about Aston and download our Application Brief below for more details on how Aston supports industry-leading sensitivity in helping to improve end point detection.

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