Skip to main content Accessibility help
×
Home
Hostname: page-component-99c86f546-7c2ld Total loading time: 0.239 Render date: 2021-11-27T16:02:44.363Z Has data issue: true Feature Flags: { "shouldUseShareProductTool": true, "shouldUseHypothesis": true, "isUnsiloEnabled": true, "metricsAbstractViews": false, "figures": true, "newCiteModal": false, "newCitedByModal": true, "newEcommerce": true, "newUsageEvents": true }

Searching Ultimate Nanometrology for AlOx Thickness in Magnetic Tunnel Junction by Analytical Electron Microscopy and X-ray Reflectometry

Published online by Cambridge University Press:  28 September 2005

Se Ahn Song
Affiliation:
Samsung Advanced Institute of Technology (SAIT), P.O. Box 111, Suwon, 440-600, Korea
Tatsumi Hirano
Affiliation:
Hitachi Research Lab. (HRL), Hitachi Ltd., Oomika-cho 7-1-1, Hitachi-shi, Ibaraki 319-1292, Japan
Jong Bong Park
Affiliation:
Samsung Advanced Institute of Technology (SAIT), P.O. Box 111, Suwon, 440-600, Korea
Kazutoshi Kaji
Affiliation:
Hitachi Research Lab. (HRL), Hitachi Ltd., Oomika-cho 7-1-1, Hitachi-shi, Ibaraki 319-1292, Japan
Ki Hong Kim
Affiliation:
Samsung Advanced Institute of Technology (SAIT), P.O. Box 111, Suwon, 440-600, Korea
Shohei Terada
Affiliation:
Hitachi Research Lab. (HRL), Hitachi Ltd., Oomika-cho 7-1-1, Hitachi-shi, Ibaraki 319-1292, Japan

Abstract

Practical analyses of the structures of ultrathin multilayers in tunneling magneto resistance (TMR) and Magnetic Random Access Memory (MRAM) devices have been a challenging task because layers are very thin, just 1–2 nm thick. Particularly, the thinness (∼1 nm) and chemical properties of the AlOx barrier layer are critical to its magnetic tunneling property. We focused on evaluating the current TEM analytical methods by measuring the thickness and composition of an AlOx layer using several TEM instruments, that is, a round robin test, and cross-checked the thickness results with an X-ray reflectometry (XRR) method. The thickness measured by using HRTEM, HAADF-STEM, and zero-loss images was 1.1 nm, which agreed with the results from the XRR method. On the other hand, TEM-EELS measurements showed 1.8 nm for an oxygen 2D-EELS image and 3.0 nm for an oxygen spatially resolved EELS image, whereas the STEM-EDS line profile showed 2.5 nm in thickness. However, after improving the TEM-EELS measurements by acquiring time-resolved images, the measured thickness of the AlOx layer was improved from 1.8 nm to 1.4 nm for the oxygen 2D-EELS image and from 3.0 nm to 2.0 nm for the spatially resolved EELS image, respectively. Also the observed thickness from the EDS line profile was improved to 1.4 nm after more careful optimization of the experimental parameters. We found that EELS and EDS of one-dimensional line scans or two-dimensional elemental mapping gave a larger AlOx thickness even though much care was taken. The reasons for larger measured values can be found from several factors such as sample drift, beam damage, probe size, beam delocalization, and multiple scattering for the EDS images, and chromatic aberration, diffraction limit due to the aperture, delocalization, alignment between layered direction in samples, and energy dispersion direction in the EELS instrument for EELS images. In the case of STEM-EDS mapping with focused nanoprobes, it is always necessary to reduce beam damage and sample drift while trying to maintain the signal-to-noise (S/N) ratio as high as possible. Also we confirmed that the time-resolved TEM-EELS acquisition technique improves S/N ratios of elemental maps without blurring the images.

Type
Special Issue: Frontiers of Electron Microscopy in Materials Science
Copyright
© 2005 Microscopy Society of America

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Bai, J., Fullerton, E.E., & Montano, P.A. (1996). Resonant X-ray reflectivity study of Fe/Cr superlattices. Physica B 221, 411415.Google Scholar
Diebold, A.C., Foran, B., Kisielowski, C., Muller, D.A., Pennycook, S.J., Principe, E., & Stemmer, S. (2003). Thin dielectric film thickness determination by advanced transmission electron microscopy. Microsc Microanal 9, 493508.Google Scholar
Dieny, B., Speriosu, V.S., Parkin, S.S.P., Gurney, B.A., Wilhoit, D.R., & Mauri, D. (1991). Giant magnetoresistive in soft ferromagnetic multilayers. Phys Rev B 43, 12971300.Google Scholar
Egerton, R.F. (1996). Electron Energy-Loss Spectroscopy in the Electron Microscope, 2nd ed. New York: Plenum Press.
Gillies, M.F. & Kuiper, A.E.T. (2000). Enhancement of the giant magnetoresistance in spin valves via oxides formed from magnetic layers. J Appl Phys 88, 58945898.Google Scholar
Hirano, T., Ueda, K., & Imagawa, T. (2003). Layered structure analysis of magnetic multilayers by X-ray scattering and TEM methods. Trans Mat Res Soc Jpn 28, 3538.Google Scholar
Hirano, T., Usami, K., Ueda, K., & Hoshiya, H. (1998). Layered structure analysis of GMR multilayers by X-ray reflectometry using the anomalous dispersion effect. J Synchrotron Rad 5, 969971.Google Scholar
Huang, T.C., Nozieres, J.-P., Speriosu, V.S., Lefakis, H., & Gurney, B.H. (1992). X-ray reflectivity analysis of giant-magnetoresistance spin-valve layered structures. Appl Phys Lett 60, 15731575.Google Scholar
Kim, Y.K., Park, G.-H., Lee, S.-R., Min, S.-H., Won, J.Y., & Song, S.A. (2003). Interface and microstructure evolutions in synthetic ferrimagnet-based spin valves upon exposure to postdeposition annealing. J Appl Phys 93, 79247926.Google Scholar
Kimoto, K., Tatsumi, H., Usami, K., & Hoshiya, H. (1994). High spatial resolution elemental mapping of multilayers using a field emission transmission electron microscope equipped with an imaging filter. Jpn J Appl Phys 33, L1642L1644.Google Scholar
Krivanek, O.L., Kundmann, M.K., & Kimoto, K. (1995). Spatial resolution in EFTEM elemental maps. J Microsc 180, 277287.Google Scholar
Moodera, J.S. & Mathon, G. (1999). Spin polarized tunneling in ferromagnetic junctions. J Magn Mater 200, 248273.Google Scholar
Névot, L. & Croce, P. (1980). Caractérisation des surfaces par réflexion rasante de rayons X. Application à l'étude du polissage de quelques verres silicates. J Rev Phys Appl 15, 761779 (in French).Google Scholar
Parkin, S.S.P., Roche, K.P., Samant, M.G., Rice, P.M., Beyers, R.B., Scheuerlein, R.E., O'Sulivan, E.J., Brown, S.L., Bucchigano, J., Abraham, D.W., Lu, Y., Rooks, M., Trouilloud, P.L., Wanner, R.A., & Gallagher, W.J. (1999). Exchange-biased magnetic tunnel junctions and application to nonvolatile magnetic random access memory. J Appl Phys 85, 58285833.Google Scholar
Parratt, L.G. (1954). Surface studies of solids by total reflection of X-rays. Phys Rev 95, 359369.Google Scholar
Pennycook, S.J. (1982). High resolution electron microscopy and microanalysis. Contemp Phys 23, 371400.Google Scholar
Plisch, M.J., Chang, J.L., Silcox, J., & Buhrman, R.A. (2001). Atomic-scale characterization of a Co/AlOx/Co magnetic tunnel junction by scanning transmission electron microscopy. Appl Phys Lett 79, 391393.Google Scholar
Reimer, L. (1995). Energy-Filtering Transmission Electron Microscopy. Berlin: Springer-Verlag.
Shen, F., Xu, Q.Y., Yu, G.H., Lai, W.Y., Zhang, Z., Lu, Z.Q., Pan, G., & Al-Jibouri, A. (2002). A specular spin valve with discontinuous nano-oxide layers. Appl Phys Lett 80, 44104412.Google Scholar
Song, S.A., Park, G.-S., Baik, H., & Sinclair, R. (2000). Resolution and contrast in GMR multilayers. In Proceedings of FEMMS2000, Abstracts, p. 96. Matsue, Japan: FEMMS 2000.
Terada, S., Aoyama, T., Yano, F., & Mitsui, Y. (2001). Time-resolved acquisition technique for elemental mapping by energy-filtering TEM. J Electron Microsc 50, 8387.Google Scholar
Terada, S., Aoyama, T., Yano, F., & Mitsui, Y. (2002). Time-resolved acquisition technique for spatially-resolved electron energy-loss spectroscopy by energy-filtering TEM. J Electron Microsc 51, 291296.Google Scholar
Usami, K., Hirano, T., Kobayashi, N., Tajima, Y., & Imagawa, T. (2000). Investigation of multi-wave X-ray reflectometry. J Magn Soc Jpn 24, 551554 (in Japanese).Google Scholar
Usami, K., Ueda, K., Hirano, T., Hoshiya, H., & Narishige, S. (1997). Layered structure analysis of multilayers by X-ray reflectometry using the Cu-Kβ line. J Magn Soc Jpn 21, 441444 (in Japanese).Google Scholar
Williams, D.B. & Carter, C.B. (1996). Transmission Electron Microscopy. New York: Plenum Press.
1
Cited by

Send article to Kindle

To send this article to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about sending to your Kindle.

Note you can select to send to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Searching Ultimate Nanometrology for AlOx Thickness in Magnetic Tunnel Junction by Analytical Electron Microscopy and X-ray Reflectometry
Available formats
×

Send article to Dropbox

To send this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Dropbox.

Searching Ultimate Nanometrology for AlOx Thickness in Magnetic Tunnel Junction by Analytical Electron Microscopy and X-ray Reflectometry
Available formats
×

Send article to Google Drive

To send this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Google Drive.

Searching Ultimate Nanometrology for AlOx Thickness in Magnetic Tunnel Junction by Analytical Electron Microscopy and X-ray Reflectometry
Available formats
×
×

Reply to: Submit a response

Please enter your response.

Your details

Please enter a valid email address.

Conflicting interests

Do you have any conflicting interests? *