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Title: Morphological instability of Ag films caused by phase transition in the underlying Ta barrier layer

Abstract

Wide-bandgap (WBG) semiconductor technologies are maturing and may provide increased device performance in many fields of applications, such as high-temperature electronics. However, there are still issues regarding the stability and reliability of WBG devices. Of particular importance is the high-temperature stability of interconnects for electronic systems based on WBG-semiconductors. For metallization without proper encapsulation, morphological degradation can occur at elevated temperatures. Sandwiching Ag films between Ta and/or TaN layers in this study is found to be electrically and morphologically stabilize the Ag metallization up to 800 °C, compared to 600 °C for uncapped films. However, the barrier layer plays a key role and TaN is found to be superior to Ta, resulting in the best achieved stability, whereas the difference between Ta and TaN caps is negligible. The β-to-α phase transition in the underlying Ta barrier layer is identified as the major cause responsible for the morphological instability observed above 600 °C. It is shown that this phase transition can be avoided using a stacked Ta/TaN barrier.

Authors:
; ; ; ; ;  [1]
  1. Solid State Electronics, The Ångström Laboratory, Uppsala University, P.O. Box 534, SE-75121 (Sweden)
Publication Date:
OSTI Identifier:
22310867
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 7; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DEPLETION LAYER; ENCAPSULATION; FILMS; INSTABILITY; PHASE TRANSFORMATIONS; RELIABILITY; SEMICONDUCTOR MATERIALS; SILVER; STABILITY; TANTALUM; TANTALUM NITRIDES

Citation Formats

Mardani, Shabnam, E-mail: shabnam.mardani@angstrom.uu.se, Vallin, Örjan, Wätjen, Jörn Timo, Norström, Hans, Olsson, Jörgen, and Zhang, Shi-Li, E-mail: shili.zhang@angstrom.uu.se. Morphological instability of Ag films caused by phase transition in the underlying Ta barrier layer. United States: N. p., 2014. Web. doi:10.1063/1.4893768.
Mardani, Shabnam, E-mail: shabnam.mardani@angstrom.uu.se, Vallin, Örjan, Wätjen, Jörn Timo, Norström, Hans, Olsson, Jörgen, & Zhang, Shi-Li, E-mail: shili.zhang@angstrom.uu.se. Morphological instability of Ag films caused by phase transition in the underlying Ta barrier layer. United States. doi:10.1063/1.4893768.
Mardani, Shabnam, E-mail: shabnam.mardani@angstrom.uu.se, Vallin, Örjan, Wätjen, Jörn Timo, Norström, Hans, Olsson, Jörgen, and Zhang, Shi-Li, E-mail: shili.zhang@angstrom.uu.se. Mon . "Morphological instability of Ag films caused by phase transition in the underlying Ta barrier layer". United States. doi:10.1063/1.4893768.
@article{osti_22310867,
title = {Morphological instability of Ag films caused by phase transition in the underlying Ta barrier layer},
author = {Mardani, Shabnam, E-mail: shabnam.mardani@angstrom.uu.se and Vallin, Örjan and Wätjen, Jörn Timo and Norström, Hans and Olsson, Jörgen and Zhang, Shi-Li, E-mail: shili.zhang@angstrom.uu.se},
abstractNote = {Wide-bandgap (WBG) semiconductor technologies are maturing and may provide increased device performance in many fields of applications, such as high-temperature electronics. However, there are still issues regarding the stability and reliability of WBG devices. Of particular importance is the high-temperature stability of interconnects for electronic systems based on WBG-semiconductors. For metallization without proper encapsulation, morphological degradation can occur at elevated temperatures. Sandwiching Ag films between Ta and/or TaN layers in this study is found to be electrically and morphologically stabilize the Ag metallization up to 800 °C, compared to 600 °C for uncapped films. However, the barrier layer plays a key role and TaN is found to be superior to Ta, resulting in the best achieved stability, whereas the difference between Ta and TaN caps is negligible. The β-to-α phase transition in the underlying Ta barrier layer is identified as the major cause responsible for the morphological instability observed above 600 °C. It is shown that this phase transition can be avoided using a stacked Ta/TaN barrier.},
doi = {10.1063/1.4893768},
journal = {Applied Physics Letters},
number = 7,
volume = 105,
place = {United States},
year = {Mon Aug 18 00:00:00 EDT 2014},
month = {Mon Aug 18 00:00:00 EDT 2014}
}
  • Ultrathin TaN and Ta 1-xAl xN y films with x = 0.21 to 0.88 were deposited by atomic layer deposition (ALD) and evaluated for Cu diffusion barrier effectiveness compared to physical vapor deposition (PVD) grown TaN. Cu diffusion barrier effectiveness was investigated using in-situ ramp anneal synchrotron X-ray diffraction (XRD) on Cu/1.8 nm barrier/Si stacks. A Kissinger-like analysis was used to assess the kinetics of Cu 3Si formation and determine the effective activation energy (E a) for Cu silicidation. Compared to the stack with a PVD TaN barrier, the stacks with the ALD films exhibited a higher crystallization temperature (Tmore » c) for Cu silicidation. The Ea values of Cu 3Si formation for stacks with the ALD films were close to the reported value for grain boundary diffusion of Cu whereas the Ea of Cu 3Si formation for the stack with PVD TaN is closer to the reported value for lattice diffusion. For 3 nm films, grazing incidence in-plane XRD showed evidence of nanocrystallites in an amorphous matrix with broad peaks corresponding to high density cubic phase for the ALD grown films and lower density hexagonal phase for the PVD grown film further elucidating the difference in initial failure mechanisms due to differences in barrier crystallinity and associated phase.« less
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  • The effect of ion irradiation (B{sup +},Cr{sup +},Ga{sup +}, and Nb{sup +}) on the crystalline structure and magnetic properties of L1{sub 0} (face-centered tetragonal structure) FePt films was investigated. Irradiating with Cr{sup +}, Ga{sup +}, and Nb{sup +} ions of less than 1 at. % (1.6x10{sup 15} ions/cm{sup 2}) dose yielded an almost ideal structural transition from the L1{sub 0} to A1 (face-centered cubic structure) phase withoutdamage to the surface of the film. This structural transition was accompanied by a change in magnetic properties from a hard magnet with a coercivity H{sub c} of {approx}7 kOe to a soft magnetmore » with H{sub c}<1 kOe. A two-dimensional pattern composed of hard magnetic L1{sub 0} and soft magnetic A1 phases was fabricated by using a focused Ga{sup +} ion beam.« less
  • No abstract prepared.