Nanofabrication of Diffractive Soft X-ray Optics

This thesis summarizes the present status of the nanofabrication of diffractive optics, i.e. zone plates, and test objects for soft x-ray microscopy at KTH. The emphasis is on new and improved fabrication processes for nickel and germanium zone plates. A new concept in which nickel and germanium are...

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Main Author: Lindblom, Magnus
Format: Doctoral Thesis
Language:English
Published: KTH, Biomedicinsk fysik och röntgenfysik 2009
Subjects:
Online Access:http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9800
http://nbn-resolving.de/urn:isbn:978-91-7415-205-0
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spelling ndltd-UPSALLA1-oai-DiVA.org-kth-98002013-01-08T13:07:54ZNanofabrication of Diffractive Soft X-ray OpticsengLindblom, MagnusKTH, Biomedicinsk fysik och röntgenfysikStockholm : KTH Royal Institute of Technology2009NanofabricationZone platex-raydiffractive x-ray opticsx-ray microscopyOpticsOptikPhysicsFysikThis thesis summarizes the present status of the nanofabrication of diffractive optics, i.e. zone plates, and test objects for soft x-ray microscopy at KTH. The emphasis is on new and improved fabrication processes for nickel and germanium zone plates. A new concept in which nickel and germanium are combined in a zone plate is also presented. The main techniques used in the fabrication are electron beam lithography for the patterning, followed by plasma etching and electroplating for the structuring of the optical materials. The process for fabricating nickel zone plates has been significantly improved. The reproducibility of the electroplating step has been increased by the implementation of an in-situ rate measurement and an end-point detection method. We have also shown that pulse plating can be used to obtain zone plates with a uniform height profile. New plating mold materials have been introduced and electron-beam curing of the molds has been investigated and implemented to increase their mechanical stability so that pattern collapse in the electroplating step can be avoided. The introduction of cold development has improved the achievable resolution of the process. This has enabled the fabrication of zone plates with outermost zone widths down to 16 nm. The nickel process has also recently been adapted to fabrication of gold structures intended for test objects and hard x-ray zone plates. For the fabrication of germanium zone plates we developed a highly anisotropic plasma-etch process using Cl2 feed and sidewall passivation. Germanium zone plates have been fabricated with zone widths down to 30 nm. The diffraction efficiency is comparable to that of nickel zone plates, but the process does not involve electroplating and thus has for potential for highyield fabrication. The combination of nickel and germanium is a new fabrication concept that provides a means to achieve high diffraction efficiency even for thin nickel. The idea is to fabricate a nickel zone plate on a germanium film. The nickel zone plate itself is then used as etch mask for a highly selective CHF3- plasma etch into the germanium layer. Proof of principle experiments showed an efficiency increase of about a factor of two for nickel zone plates with a 50- nm nickel thickness. QC 20100728Doctoral thesis, comprehensive summaryinfo:eu-repo/semantics/doctoralThesistexthttp://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9800urn:isbn:978-91-7415-205-0Trita-FYS, 0280-316X ; 2008:57application/pdfinfo:eu-repo/semantics/openAccess
collection NDLTD
language English
format Doctoral Thesis
sources NDLTD
topic Nanofabrication
Zone plate
x-ray
diffractive x-ray optics
x-ray microscopy
Optics
Optik
Physics
Fysik
spellingShingle Nanofabrication
Zone plate
x-ray
diffractive x-ray optics
x-ray microscopy
Optics
Optik
Physics
Fysik
Lindblom, Magnus
Nanofabrication of Diffractive Soft X-ray Optics
description This thesis summarizes the present status of the nanofabrication of diffractive optics, i.e. zone plates, and test objects for soft x-ray microscopy at KTH. The emphasis is on new and improved fabrication processes for nickel and germanium zone plates. A new concept in which nickel and germanium are combined in a zone plate is also presented. The main techniques used in the fabrication are electron beam lithography for the patterning, followed by plasma etching and electroplating for the structuring of the optical materials. The process for fabricating nickel zone plates has been significantly improved. The reproducibility of the electroplating step has been increased by the implementation of an in-situ rate measurement and an end-point detection method. We have also shown that pulse plating can be used to obtain zone plates with a uniform height profile. New plating mold materials have been introduced and electron-beam curing of the molds has been investigated and implemented to increase their mechanical stability so that pattern collapse in the electroplating step can be avoided. The introduction of cold development has improved the achievable resolution of the process. This has enabled the fabrication of zone plates with outermost zone widths down to 16 nm. The nickel process has also recently been adapted to fabrication of gold structures intended for test objects and hard x-ray zone plates. For the fabrication of germanium zone plates we developed a highly anisotropic plasma-etch process using Cl2 feed and sidewall passivation. Germanium zone plates have been fabricated with zone widths down to 30 nm. The diffraction efficiency is comparable to that of nickel zone plates, but the process does not involve electroplating and thus has for potential for highyield fabrication. The combination of nickel and germanium is a new fabrication concept that provides a means to achieve high diffraction efficiency even for thin nickel. The idea is to fabricate a nickel zone plate on a germanium film. The nickel zone plate itself is then used as etch mask for a highly selective CHF3- plasma etch into the germanium layer. Proof of principle experiments showed an efficiency increase of about a factor of two for nickel zone plates with a 50- nm nickel thickness. === QC 20100728
author Lindblom, Magnus
author_facet Lindblom, Magnus
author_sort Lindblom, Magnus
title Nanofabrication of Diffractive Soft X-ray Optics
title_short Nanofabrication of Diffractive Soft X-ray Optics
title_full Nanofabrication of Diffractive Soft X-ray Optics
title_fullStr Nanofabrication of Diffractive Soft X-ray Optics
title_full_unstemmed Nanofabrication of Diffractive Soft X-ray Optics
title_sort nanofabrication of diffractive soft x-ray optics
publisher KTH, Biomedicinsk fysik och röntgenfysik
publishDate 2009
url http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9800
http://nbn-resolving.de/urn:isbn:978-91-7415-205-0
work_keys_str_mv AT lindblommagnus nanofabricationofdiffractivesoftxrayoptics
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