Study of a linear surface wave plasma source for tin removal in an extreme ultraviolet source
- Univ. of Illinois at Urbana-Champaign, IL (United States)
Tin deposition mitigation employs hydrogen radicals and ions, formed in a hydrogen plasma, to interact with tin to form tin hydride (SnH4) in the gaseous state, which is then pumped away. Surface wave plasma (SWP) technology developed at Illinois generates hydrogen radicals and ions, resulting in tin etch rates that are high enough to keep extreme ultraviolet (EUV) lithographic tools clean. An advantage of an SWP antenna is the ability to generate a high density of hydrogen radicals and hydrogen ions directly at the desired etching location. In situ etching of tin enables high availability EUV tools by maintaining high reflectivity of the multilayer mirror of the collector. Additionally, the SWP is characterized with low ion energies and low electron temperature, such that the multilayer mirror does not suffer any damage from sputtering or implantation of hydrogen ions during operation. Here, experiments elucidating the fundamental processes of tin removal are conducted by varying pressure, power, surface temperature, and gas flow rate in order to observe the etch rate behavior. Our results have shown that the presence of hydrogen ions increases etch rates because ion bombardment weakens Sn–Sn bonds, which, in turn, allows for a higher rate of chemical etching by the radicals. The ion bombardment reduces the number of radicals needed to etch a single tin atom to the range of 102 –103. The linear SWP antenna yields plasma densities on the order of 1017 to 1018 m-3 and radical densities on the order of 1018 to 1019 m-3, allowing for greater utilization of ion etch enhancement. Etch rates of up to 200 nm/min have been achieved. The surface temperature of the samples is an important factor in the etching process such that the decrease in the surface temperature increases the etch rates and decreases the hydrogen desorption rates. In addition, a kinetic etch model is developed to explain the behavior of etch rates as a function of surface temperature. Furthermore, results from experiments performed in an Illinois NXE:3100 chamber will be discussed.
- Research Organization:
- Univ. of Illinois at Urbana-Champaign, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- Grant/Contract Number:
- FG02-07ER46453; FG02-07ER46471; DEFG02-07ER46453
- OSTI ID:
- 1800514
- Alternate ID(s):
- OSTI ID: 1648600
- Journal Information:
- Journal of Vacuum Science and Technology B, Vol. 38, Issue 5; ISSN 2166-2746
- Publisher:
- American Vacuum Society / AIPCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Similar Records
Direct photoetching of polymers using radiation of high energy density from a table-top extreme ultraviolet plasma source
Tin removal from extreme ultraviolet collector optics by inductively coupled plasma reactive ion etching