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TSMC EUV Mask Dry Clean

Fred Chen


TSMC develops dry-clean technique for EUV mask

Monica Chen, Hsinchu; Jessie Shen, DIGITIMES
Monday 3 August 2020

TSMC has developed what the company claims is the world's first environmental-friendly "dry-clean technique for EUV mask" to replace the traditional clean process.

Through fall-on analysis and contamination source elimination, the fall-on count of each 10,000 wafers decreased from hundreds of particles to single-digit particles, which achieved 99% of reduction rate. Since its introduction, the amount of water-saving and chemical usage saving has reached about 735 metric tons and 36 metric tons, respectively, according to the company.

EUV photomask can be divided into two types - one with pellicle and one without. TSMC has chosen EUV mask without pellicle to enhance optical transmittance, reducing energy loss during exposure. To resolve the fall-on issue, TSMC said it started developing the fall-on analysis technique in 2018.

The company said fall-on particles are rapidly removed by such a dry clean technique, and the fall-on source is precisely located by sub-nanometer analysis, which can exclude contaminations. It said it has achieved a fall-on particle reduction rate of more than 99% in 2020.

Thanks to the dry-clean technique, TSMC said it has enhanced resource utilization efficiency dramatically. Since its introduction in 2018, the duty cycle of EUV mask has increased more than 80%, and the lifetime for advanced process EUV mask has also extended, generating an accumulated NT$2 billion (US$68 million) of improvement effect, it said.

In 2019, TSMC developed automation of its dry-clean technique for EUV mask, and the automated production system was introduced to all 12-inch wafer fabs in January 2020.


I do believe "EUV mask Dry Clean" process is a complement not replacement of traditional " Wet Clean" due to some detrimental side-effect of clean chemicals.

Fred Chen

Without a pellicle, patterned inspection is necessary, every 10000 wafers apparently. Inspection is needed to check after cleaning as well, obviously. Some fall-ons are inevitable from the inspection itself (previous dirty masks).
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