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Controlled electroplating for high-aspect-ratio zone plate fabrication
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.ORCID-id: 0000-0003-2745-6289
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.ORCID-id: 0000-0003-2723-6622
2006 (engelsk)Inngår i: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 24, nr 6, s. 2592-2596Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The authors report a method for monitoring, control, and end-point detection of electroplating in nanostructures. The method is demonstrated on nickel plating into polymer molds, which is an important process in the fabrication of soft x-ray zone-plate diffractive optics. The lack of reproducibility presently limits the achievable nickel aspect ratio and, thus, reduces the zone-plate diffraction efficiency. The reported method provides reproducible plating via real-time control of the plating rate. It combines in situ light transmission measurements with current measurements to determine the thickness of the growing layer. The accuracy of the thickness prediction was better than ±4% (1) for 100–300  nm nickel layers. Furthermore, a slight change in the light transmission signal indicates when a gratinglike zone-plate structure is slightly overplated and the plating should be stopped. This end-point detection provides the optimal filling of high-aspect-ratio molds for improved diffraction efficiency.

sted, utgiver, år, opplag, sider
2006. Vol. 24, nr 6, s. 2592-2596
Emneord [en]
X-RAY MICROSCOPY; HIGH-EFFICIENCY; CONDENSER; OPTICS
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-5987DOI: 10.1116/1.2362761ISI: 000243324400017Scopus ID: 2-s2.0-33845257285OAI: oai:DiVA.org:kth-5987DiVA, id: diva2:10543
Merknad
QC 20100616Tilgjengelig fra: 2006-06-08 Laget: 2006-06-08 Sist oppdatert: 2020-01-30bibliografisk kontrollert
Inngår i avhandling
1. Nanofabrication of Diffractive Soft X-ray Optics
Åpne denne publikasjonen i ny fane eller vindu >>Nanofabrication of Diffractive Soft X-ray Optics
2009 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

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.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2009. s. vii, 71
Serie
Trita-FYS, ISSN 0280-316X ; 2008:57
Emneord
Nanofabrication, Zone plate, x-ray, diffractive x-ray optics, x-ray microscopy
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-9800 (URN)978-91-7415-205-0 (ISBN)
Disputas
2009-02-06, FR4, Roslagstullsbacken 21, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Merknad
QC 20100728Tilgjengelig fra: 2009-01-13 Laget: 2009-01-07 Sist oppdatert: 2011-10-20bibliografisk kontrollert
2. Nanofabrication of Zone Plate Optics for Compact Soft X-Ray Microscopy
Åpne denne publikasjonen i ny fane eller vindu >>Nanofabrication of Zone Plate Optics for Compact Soft X-Ray Microscopy
2006 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

This Thesis describes the development of the KTH/Stockholm nanofabrication process for diffractive soft x-ray optics. The effort is motivated by the need for and requirement of specially designed diffractive optics and test objects for compact x-ray microscopy as well as optics for other applications such as phase imaging. The optics have been fabricated in-house, in the KTH Nanofabrication Laboratory.

The nanofabrication process is based on electron-beam lithography in combination with reactive ion etching (RIE) and nickel electroplating. This process has successfully been used for the fabrication of micro zone plates, condenser zone plates, diffractive optical elements for differential-interference microscopy, and different test structures. Optics with electroplated feature sizes down to 25 nm have been fabricated with high aspect-ratios. Special consideration has been given the reproducibility and optimization of the process parameters. This is essential for improving the yield and quality of the fabricated optics. The work includes, e.g., improved e-beam writing strategies and controlled electroplating. Furthermore, a high diffraction efficiency is necessary for our applications, which are based on compact low-power sources. This requires the fabrication of optics with a high and uniform aspect ratio. For this purpose the electroplating process step has been improved with an in-situ light-transmission-based thickness control method for optimum mold filling, and pulse and pulse-reverse techniques for uniform plating.

sted, utgiver, år, opplag, sider
Stockholm: KTH, 2006
Serie
Trita-FYS, ISSN 0280-316X ; 2006:41
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-4045 (URN)91-7178-390-3 (ISBN)
Disputas
2006-06-16, Sal FD5, AlbaNova univ centrum, Roslagstullsbacken 21, Stockholm, 10:00
Opponent
Veileder
Merknad
QC 20100616Tilgjengelig fra: 2006-06-08 Laget: 2006-06-08 Sist oppdatert: 2020-01-30bibliografisk kontrollert

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