Cryogenic Etching of the Electroplating Mold for Improved Zone Plate Lenses
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
The fabrication of zone plate lenses that are used for focusing X-rays relies on nanofabrication techniques such as e-beam lithography, reactive ion etching, and electroplating. The circular grating-like zone plate pattern can have a smallest half-period, a so-called zone width, of down to 20 nm while it also needs to have a height that is 5 to 10 times the zone width to have good diffraction efficiency. This high aspect ratio structuring is a very challenging field of nanofabrication.
This diploma project has focused on improving the process step of fabricating the electroplating mold by cryo-cooling the polymer during the reactive ion etching with O2. The low temperature causes passivation of the sidewalls of the mold during etching which results in a more ideal rectangular profile of the high aspect ratio plating mold.
By etching at -100 °C, structures with highly vertical sidewalls and no undercut were realized. The experiments showed that there is a tradeoff between the anisotropy of the zone profile and the formation rate of polymer residue, so-called RIE grass. Through a proper choice of process parameters the grass could be completely removed without introducing any undercut.
Place, publisher, year, edition, pages
2010. , 40 p.
Trita-FYS, ISSN 0280-316X ; 2010:09
etching, plasma etching, zone plate, x-ray, nanofabrication, sidewall passivation, cryo, cryogenic, undercut
Other Engineering and Technologies Condensed Matter Physics
IdentifiersURN: urn:nbn:se:kth:diva-12109ISRN: KTH/FYS/--10:09--SEOAI: oai:DiVA.org:kth-12109DiVA: diva2:302193
UppsokPhysics, Chemistry, Mathematics
Holmberg, Anders, Dr.
Hertz, Hans, Prof.