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Title: Plasma-assisted atomic layer epitaxial growth of aluminum nitride studied with real time grazing angle small angle x-ray scattering

Abstract

Wide bandgap semiconducting nitrides have found wide-spread application as light emitting and laser diodes and are under investigation for further application in optoelectronics, photovoltaics, and efficient power switching technologies. Alloys of the binary semiconductors allow adjustments of the band gap, an important semiconductor material characteristic, which is 6.2 eV for aluminum nitride (AlN), 3.4 eV for gallium nitride, and 0.7 eV for (InN). Currently, the highest quality III-nitride films are deposited by metalorganic chemical vapor deposition and molecular beam epitaxy. Temperatures of 900 °C and higher are required to deposit high quality AlN. Research into depositing III-nitrides with atomic layer epitaxy (ALEp) is ongoing because it is a fabrication friendly technique allowing lower growth temperatures. Because it is a relatively new technique, there is insufficient understanding of the ALEp growth mechanism which will be essential to development of the process. Here, grazing incidence small angle x-ray scattering is employed to observe the evolving behavior of the surface morphology during growth of AlN by ALEp at temperatures from 360 to 480 °C. Increased temperatures of AlN resulted in lower impurities and relatively fewer features with short range correlations.

Authors:
; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1409581
Report Number(s):
BNL-114633-2017-JA¿¿¿
Journal ID: ISSN 0734-2101
DOE Contract Number:
SC0012704
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films; Journal Volume: 35; Journal Issue: 3
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Anderson, Virginia R., Nepal, Neeraj, Johnson, Scooter D., Robinson, Zachary R., Nath, Anindya, Kozen, Alexander C., Qadri, Syed B., DeMasi, Alexander, Hite, Jennifer K., Ludwig, Karl F., and Eddy, Charles R.. Plasma-assisted atomic layer epitaxial growth of aluminum nitride studied with real time grazing angle small angle x-ray scattering. United States: N. p., 2017. Web. doi:10.1116/1.4979007.
Anderson, Virginia R., Nepal, Neeraj, Johnson, Scooter D., Robinson, Zachary R., Nath, Anindya, Kozen, Alexander C., Qadri, Syed B., DeMasi, Alexander, Hite, Jennifer K., Ludwig, Karl F., & Eddy, Charles R.. Plasma-assisted atomic layer epitaxial growth of aluminum nitride studied with real time grazing angle small angle x-ray scattering. United States. doi:10.1116/1.4979007.
Anderson, Virginia R., Nepal, Neeraj, Johnson, Scooter D., Robinson, Zachary R., Nath, Anindya, Kozen, Alexander C., Qadri, Syed B., DeMasi, Alexander, Hite, Jennifer K., Ludwig, Karl F., and Eddy, Charles R.. Mon . "Plasma-assisted atomic layer epitaxial growth of aluminum nitride studied with real time grazing angle small angle x-ray scattering". United States. doi:10.1116/1.4979007.
@article{osti_1409581,
title = {Plasma-assisted atomic layer epitaxial growth of aluminum nitride studied with real time grazing angle small angle x-ray scattering},
author = {Anderson, Virginia R. and Nepal, Neeraj and Johnson, Scooter D. and Robinson, Zachary R. and Nath, Anindya and Kozen, Alexander C. and Qadri, Syed B. and DeMasi, Alexander and Hite, Jennifer K. and Ludwig, Karl F. and Eddy, Charles R.},
abstractNote = {Wide bandgap semiconducting nitrides have found wide-spread application as light emitting and laser diodes and are under investigation for further application in optoelectronics, photovoltaics, and efficient power switching technologies. Alloys of the binary semiconductors allow adjustments of the band gap, an important semiconductor material characteristic, which is 6.2 eV for aluminum nitride (AlN), 3.4 eV for gallium nitride, and 0.7 eV for (InN). Currently, the highest quality III-nitride films are deposited by metalorganic chemical vapor deposition and molecular beam epitaxy. Temperatures of 900 °C and higher are required to deposit high quality AlN. Research into depositing III-nitrides with atomic layer epitaxy (ALEp) is ongoing because it is a fabrication friendly technique allowing lower growth temperatures. Because it is a relatively new technique, there is insufficient understanding of the ALEp growth mechanism which will be essential to development of the process. Here, grazing incidence small angle x-ray scattering is employed to observe the evolving behavior of the surface morphology during growth of AlN by ALEp at temperatures from 360 to 480 °C. Increased temperatures of AlN resulted in lower impurities and relatively fewer features with short range correlations.},
doi = {10.1116/1.4979007},
journal = {Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films},
number = 3,
volume = 35,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2017},
month = {Mon May 01 00:00:00 EDT 2017}
}
  • New results are presented for the annealing behavior of ultrathin complementary-metal-oxide-semiconductor (CMOS) gate dielectric HfO{sub 2} films grown by atomic layer deposition (ALD). A series of ALD HfO{sub 2} dielectric films has been studied by a combination of x-ray reflectivity (XRR) and grazing-incidence small-angle x-ray scattering (GISAXS) measurements. By using these techniques together, we have shown that the surface, interfaces, and internal structure of thin ALD films can be characterized with unprecedented sensitivity. Changes in film thickness, film roughness, or diffuseness of the film/substrate interface as measured by XRR are correlated with the corresponding changes in the internal film nanostructure,more » as measured by GISAXS. Although the films are dense, an internal film structure is shown to exist, attributed primarily to {approx} 2 nm 'missing island' porosity features close to the substrate; these are most likely associated with coalescence defects as a result of initial ALD growth, as they are not observed in the upper regions of the film. Some 8-9 nm heterogeneities are also present, which may indicate a widespread modulation in the film density pervading the entire film volume, and which likely also give rise to surface roughness. Comparison of the data between different scattering geometries and among a carefully designed sequence of samples has enabled important insights to be derived for the annealing behavior of the ALD HfO{sub 2} films. The main effects of single, brief, high temperature excursions to above 900C are to anneal out some of the fine voids and reduce the mean roughness and interfacial diffuseness of the film. These changes are indicative of densification. However, depending on the film thickness, the annealing behavior at temperatures between 650 and 800C is quite different for single excursion and cyclic anneals. Particularly for thin, just-coalesced films, XRR indicates marked increases in the film thickness and in the mean roughness/diffuseness dimension for cyclic anneals. GISAXS also shows an increase, rather than a reduction, in the void microstructure under these conditions. These changes in the film microstructure appear sufficient to overcome the expected film densification at elevated temperatures with implications for the gate dielectric performance of the films after extended high temperature exposure and cycling, as may occur during gate dielectric fabrication.« less
  • The temporal evolution of high quality indium nitride (InN) growth by plasma-assisted atomic layer epitaxy (ALEp) on a-plane sapphire at 200 and 248 °C was probed by synchrotron x-ray methods. The growth was carried out in a thin film growth facility installed at beamline X21 of the National Synchrotron Light Source at Brookhaven National Laboratory and at beamline G3 of the Cornell High Energy Synchrotron Source, Cornell University. Measurements of grazing incidence small angle x-ray scattering (GISAXS) during the initial cycles of growth revealed a broadening and scattering near the diffuse specular rod and the development of scattering intensities duemore » to half unit cell thick nucleation islands in the Yoneda wing with correlation length scale of 7.1 and 8.2 nm, at growth temperatures (Tg) of 200 and 248 °C, respectively. At about 1.1 nm (two unit cells) of growth thickness nucleation islands coarsen, grow, and the intensity of correlated scattering peak increased at the correlation length scale of 8.0 and 8.7 nm for Tg = 200 and 248 °C, respectively. The correlated peaks at both growth temperatures can be fitted with a single peak Lorentzian function, which support single mode growth. Post-growth in situ x-ray reflectivity measurements indicate a growth rate of ~0.36 Å/cycle consistent with the growth rate previously reported for self-limited InN growth in a commercial ALEp reactor. Consistent with the in situ GISAXS study, ex situ atomic force microscopy power spectral density measurements also indicate single mode growth. Electrical characterization of the resulting film revealed an electron mobility of 50 cm2/V s for a 5.6 nm thick InN film on a-plane sapphire, which is higher than the previously reported mobility of much thicker InN films grown at higher temperature by molecular beam epitaxy directly on sapphire. These early results indicated that in situ synchrotron x-ray study of the epitaxial growth kinetics of InN films is a very powerful method to understand nucleation and growth mechanisms of ALEp to enable improvement in material quality and broaden its application.« less