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Growth morphology of thin gold films prepared by pulse plating
Abstracts of the Scadinaviun Socict?, for Elcc trot1 Microscopic
174
HIGH-PERFORMANCE CRY0 TRANSMISSION ELECTRON MICROSCOPY
Electron
8.
Microscopy,
GIT Suppl.
u. B. Hezel, E. Zellmann D. Hoffmeister Department Oberkochen,
of Microscopy, FRG
Carl
Zeiss,
3. 4. 5. 6. 7.
4
(1984)
32-34.
GROWTH MORPHOLOGY OF THIN GOLD FILMS PREPARED BY PULSE PLATING G. Holmbom
2.
and DGE.
and
Chemical fixation, resin embedding and subsequent staining with heavy metals can both produce artefacts and limit the resolution of the electron microTherefore, the obscopic specimen'-5. jective is thus to observe the specimens in the electron microscope in the frozen-hydrated state, the one most similar to the native state. All preparation steps such as cryofixation, cryosectioning and cryotransfer to the cryo-transmission electron microscope (CryoTEM) should be performed below 145K5 in order to observe the specimen in a matrix of vitrified ice avoiding any crystallization arteIn the CryoTEM itself the temfacts. perature of the frozen-hydrated specimen shouldbe kept much lower to avoid devitrification caused by the electron beam.' To meet all these requirements a special cryo-transfer system and cryostage for the Zeiss transmission electron microscope EM10 have been developed.7r* The cryotransfer from the cryochamber of a cryoultramicrotome or a cryofixation system is performed at <120K, sealed from the atmospheric humid air. The cryostage in the TEM is kept at <108K by thermal contact with the liquid This cryostage nitrogen in the Dewar. is surrounded by effective anticontaminator cooling plates (<120K, area ca. 400cm*). Because of the rotationsymmetrical stage and excellent electronic stabilisation of the temperaturetheguaranteed line resolution of this cryosystem is 0.344nm at 108K. Results from frozen-hydrated sections and suspensions are presented. 1.
SBME
U. B. Hezel, E. D. Zellmann, D. Hoffmeister,
J. Dubochet et al., J. Microscop. 128 (1982) 219. J. Lepault et al., J. Microscop. 129 (1983) 89. M. Adrian et al., Nature, in press. A. W. McDowall et al., J. Microscop. 131 (1983) 1. J. Dubochet et al., J. Bacterial. 155 (1983) 381. ,K. Zierold, GIT Lab-Med. 5 (1982) 337. E. Giitter and D. Hoffmeister, Lecture 16.9.83 Antwerpen, Joint Meetinq on
Linksping of Dept. nology,
and B. E. Jacobson Institute of Technology, Materials Science and TechS-581 83 Linksping
Thin films of gold are used in large amounts by the electronic industry as contact material. The films are prepared by electroplating. For economic reasons, it is desirable to minimize as far as possible the thickness of those films. However, dense, diffusionfree films with good mechanical, wearresistant properties are required. The problems in production are to minimize the number of porosities in the film and to prepare a film with a smooth surface and an even thickness. The chemical composition of the platingt,ath is, of course, important for the film growth conditions. However, the characteristics of the current used during plating will also determine the structural features and, therefore, the properties of the film. In this study, l-125 micron thick gold films were prepared using various current wave forms in order to see their effect on the nucleation and the growth process. The films were deposited onto nickel-coated copper-epoxy laminates. To fully understand the nucleation and growth process it was important to obtain a microstructural view both parallel and perpendicular to the growth direction. This was, however, not a trivial problem because gold is a soft material which easily smears out during sample preparation. Furthermore, in most cases the films This were not fully flat and dense. paperpresents the procedure used for those TEM sample preparations. Three characteristic structures were identified and arc discussed in relation to the pulse plating parameters used. Acknowledgements. Financial support for thiswork from National Swedish Board for Technical Development and the companies ASEA AB, FFV Materialteknik, IMASA Kemi AB, Kemiska AB Candor, Kraftelektronik AB, LM Ericsson, Saab-Scania AB is gratefully acknowledged.
174
HIGH-PERFORMANCE CRY0 TRANSMISSION ELECTRON MICROSCOPY
Electron
8.
Microscopy,
GIT Suppl.
u. B. Hezel, E. Zellmann D. Hoffmeister Department Oberkochen,
of Microscopy, FRG
Carl
Zeiss,
3. 4. 5. 6. 7.
4
(1984)
32-34.
GROWTH MORPHOLOGY OF THIN GOLD FILMS PREPARED BY PULSE PLATING G. Holmbom
2.
and DGE.
and
Chemical fixation, resin embedding and subsequent staining with heavy metals can both produce artefacts and limit the resolution of the electron microTherefore, the obscopic specimen'-5. jective is thus to observe the specimens in the electron microscope in the frozen-hydrated state, the one most similar to the native state. All preparation steps such as cryofixation, cryosectioning and cryotransfer to the cryo-transmission electron microscope (CryoTEM) should be performed below 145K5 in order to observe the specimen in a matrix of vitrified ice avoiding any crystallization arteIn the CryoTEM itself the temfacts. perature of the frozen-hydrated specimen shouldbe kept much lower to avoid devitrification caused by the electron beam.' To meet all these requirements a special cryo-transfer system and cryostage for the Zeiss transmission electron microscope EM10 have been developed.7r* The cryotransfer from the cryochamber of a cryoultramicrotome or a cryofixation system is performed at <120K, sealed from the atmospheric humid air. The cryostage in the TEM is kept at <108K by thermal contact with the liquid This cryostage nitrogen in the Dewar. is surrounded by effective anticontaminator cooling plates (<120K, area ca. 400cm*). Because of the rotationsymmetrical stage and excellent electronic stabilisation of the temperaturetheguaranteed line resolution of this cryosystem is 0.344nm at 108K. Results from frozen-hydrated sections and suspensions are presented. 1.
SBME
U. B. Hezel, E. D. Zellmann, D. Hoffmeister,
J. Dubochet et al., J. Microscop. 128 (1982) 219. J. Lepault et al., J. Microscop. 129 (1983) 89. M. Adrian et al., Nature, in press. A. W. McDowall et al., J. Microscop. 131 (1983) 1. J. Dubochet et al., J. Bacterial. 155 (1983) 381. ,K. Zierold, GIT Lab-Med. 5 (1982) 337. E. Giitter and D. Hoffmeister, Lecture 16.9.83 Antwerpen, Joint Meetinq on
Linksping of Dept. nology,
and B. E. Jacobson Institute of Technology, Materials Science and TechS-581 83 Linksping
Thin films of gold are used in large amounts by the electronic industry as contact material. The films are prepared by electroplating. For economic reasons, it is desirable to minimize as far as possible the thickness of those films. However, dense, diffusionfree films with good mechanical, wearresistant properties are required. The problems in production are to minimize the number of porosities in the film and to prepare a film with a smooth surface and an even thickness. The chemical composition of the platingt,ath is, of course, important for the film growth conditions. However, the characteristics of the current used during plating will also determine the structural features and, therefore, the properties of the film. In this study, l-125 micron thick gold films were prepared using various current wave forms in order to see their effect on the nucleation and the growth process. The films were deposited onto nickel-coated copper-epoxy laminates. To fully understand the nucleation and growth process it was important to obtain a microstructural view both parallel and perpendicular to the growth direction. This was, however, not a trivial problem because gold is a soft material which easily smears out during sample preparation. Furthermore, in most cases the films This were not fully flat and dense. paperpresents the procedure used for those TEM sample preparations. Three characteristic structures were identified and arc discussed in relation to the pulse plating parameters used. Acknowledgements. Financial support for thiswork from National Swedish Board for Technical Development and the companies ASEA AB, FFV Materialteknik, IMASA Kemi AB, Kemiska AB Candor, Kraftelektronik AB, LM Ericsson, Saab-Scania AB is gratefully acknowledged.