Ведущие производители чипов присматриваются к фотолитографии в глубоком ультрафиолете

«Чтобы на зеркале не скапливались остатки олова, его постоянно продувают водородом.»

Звучит странно, но там должен быть вакуум. Фраза есть в оригинале статьи, но без уточнений http://spectrum.ieee.org/semiconductors/devices/leading-chipmakers-eye-euv-lithography-to-save-moores-law "Because the approach generates EUV light as well as tin debris, hydrogen gas constantly flows across the collector mirror to keep it from being rapidly covered with a layer of tin."

Есть статьи об очистке зеркала коллектора внутри установки (внедрено), но не во время работы источника — http://cpmi.illinois.edu/files/2016/03/In-Situ-Collector-Cleaning-and-EUV-Reflectivity-Restoration-by-Hydrogen-Plasma-for-EUV-Sources.pdf "In situ collector cleaning and extreme ultraviolet reflectivity restoration by hydrogen plasma for extreme ultraviolet sources", 2016, http://dx.doi.org/10.1116/1.4942456

While debris mitigation techniques such as magnetic mitigation (to deflect ions) and buffer gas (to deflect neutrals) exist,11,12 no debris mitigation technique can completely eliminate Sn deposition on the collector. Thus, as Sn accumulates, EUV power at the wafer is reduced until the collector must be either cleaned or replaced, incurring costs and downtime. The best way to minimize downtime is to clean the collector while in the chamber (in situ).… For the experiments shown in this paper, the hydrogen pressure was 65 mTorr, and the flow rate was 500 sccm

Cymer (производитель EUV источников) писал о водороде:
http://optics.org/news/2/4/31 "We have previously disclosed that Cymer uses a hydrogen buffer-gas background to decelerate the high-speed ions that come out of the plasma, and keep them from eroding the collector and its multilayer reflective coating. There is also a high-speed H2 flow to help keep atomic tin away from the collector surface."
Точные давления газа не раскрывались: https://www.cymer.com/wp-content/uploads/2016/07/Cymer_SPIE_AdvancedLithography_2010.pdf#page=24 Fomenkov "Laser Produced Plasma Light Source for EUVL" / SPIE Advanced Lithography, 2011. doi:10.1117/12.882210: "Our debris mitigation system works by the use of hydrogen buffer gas to stop high energy fast ions… Figure 10: Hydrogen buffer gas pressure vs. ion energy and flux at the location of the collector surface"
https://www.cymer.com/wp-content/uploads/2016/07/Cymer_SPIE_AdvancedLithography_2013.pdf "CO2 / Sn LPP EUV Sources for device development and HVM", SPIE Advanced Lithography. 2013 doi:10.1117/12.2011212 "Debris mitigation consisting of hydrogen gas at a given pressure and flow rate provides the protection needed to keep the optic clean and damage free over its lifetime… symmetric pumping of the hydrogen gas… Hydrogen gas is used as the primary mechanism for collector protection.… the gas pressure between the plasma and the MLM surface stops fast ions and high energy particles… hydrogen radicals; these radicals react with tin to form Stannane (SnH4), which is volatile and is thus carried away from the MLM surface with the flow of gas"

В патенте Cymer 2007 (2010) US7671349 пишут: "gas comprises hydrogen and the pressure is greater than 100 mTorr.… gas flow rate is greater than 100 sccm.… hydrogen, deuterium, helium and combinations". На Fig 1 (2я илл.) показана система удаления газа — 102 "regulated gas source 100 for introducing a gas into the chamber 26 and an adjustable pump 102 for removing gas from the chamber 26."
Gigaphoton оценивал поток водорода как 100slm 100Pa: http://www.euvlitho.com/2014/S2.pdf#page=16

От источника в литограф с основной оптической системой EUV излучение передается через небольшое отверстие на заметном расстоянии от плазмы олова — http://www.nature.com/nphoton/journal/v4/n1/images/nphoton.2009.251-f2.jpg — Intermediate focus (IF, порядка 1 см; илл. из EUV lithography: Lithography gets extreme, Christian Wagner & Noreen Harned, Nature Photonics 4, 24 — 26 (2010) doi:10.1038/nphoton.2009.251).
В более реальном масштабе это выглядит примерно так (источник справа снизу, от IF луч идет на First scanner mirror в составе Illuminator): http://spectrum.ieee.org/image/MjgyMzI5MQ.jpeg
Применяют множество систем для снижения загрязнения оловом: Repeller Field (Еще Repeller Field), Mechanical baffles + Foil Trap (Еще Foil Trap), проекты магнитных систем удаления Sn-тумана (Gigaphoton) (подумаешь, пару сверхпроводящих магнитов в каждый литограф...) и другие, более непонятные технологии: Cymer 2005, 2008 US7453077 "The noble gas may be introduced, e.g., in front of the intermediate focus (IF) 40 in a short region between two (or more) apertures, the intermediate focus aperture 150 and a cone aperture 152 at the terminus of an intermediate focus cone 160."

ASML пишет, что при помощи откачки удается поддерживать вакуум http://www.euvlitho.com/2016/P2.pdf#page=45 Igor Fomenkov, EUVL Exposure Tools for HVM: Status and Outlook, EUVL Workshop 2016 — "Hydrogen buffer gas causes deceleration of ions… Vessel with vacuum pumping to remove hot gas and tin vapor. Internal hardware to collect micro particles"

PS: Получается, ASML NXE 3300 на EUV может не более 400 мм2 засвечивать ("(26x16.5) mm expose field")? Для NXE 3350 пишут уже стандартные 26х33 мм.