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TEM Analysis of Deformation in Thin Films of Aluminum after both AC Thermomechanical and Tensile Deformation

Published

Author(s)

Roy H. Geiss, Robert Keller, David T. Read, Yi-Wen Cheng

Abstract

Thin films of sputtered aluminum were deformed by two distinctly different experimental techniques. One experiment comprised of passing high electrical AC current density, 12.2 MA/cm2 at 100 Hz, through 800 ¿¿m long X 3.3 ¿¿m wide and 0.5 ¿¿m thick patterned interconnect Al lines deposited on SiO2/Si substrates. The other consisted of mechanical tensile deformation of a free standing Al line 50 ¿¿m long X 5 ¿¿m wide and 0.5 ¿¿m thick at a strain rate of about 10-4/sec. In the electrical tests approximately 3X107 W/cm2 of energy was deposited at 200 Hz resulting in cyclic Joule heating, which developed a total thermomechanical strain of about 0.3 % per cycle. The mechanical test showed a fracture strain of only 0.5 % but did display ductile chisel point fracture. In both experiments, certain grains exhibited large, greater than 30 degrees, rotation away from an initial <111> orientation toward <001>, based on EBSD measurements. TEM analysis of specimens from both experiments showed an unusually high density of prismatic dislocation loops. In the mechanically-tested samples, a high density of loops was seen in the chisel point fracture zone. While in cross sections of highly deformed regions of the electrical test specimens, very high densities, >1015/cm3, of small, <10nm diameter, prismatic loops were observed. In both cases the presence of a high density of prismatic loops shows that a very high density of vacancies was created in the deformation. On the other hand, in both cases the density of dislocations in the deformed areas was relatively low. These results suggest very high incidence of intersecting dislocations creating jogs and subsequently vacancies before exiting the sample. A discussion of this as well as other possible sources of the high vacancy concentration will be presented.
Proceedings Title
Thin Films - Stresses and Mechanical Properties XI
Volume
863
Conference Dates
March 28-April 1, 2005
Conference Location
San Francisco, CA, USA
Conference Title
Mater. Res. Soc. Conf.

Keywords

EBSD, prismatic loops, TEM, tensile testing, thermomechanical fatigue, thin films

Citation

Geiss, R. , Keller, R. , Read, D. and Cheng, Y. (2005), TEM Analysis of Deformation in Thin Films of Aluminum after both AC Thermomechanical and Tensile Deformation, Thin Films - Stresses and Mechanical Properties XI, San Francisco, CA, USA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=50149 (Accessed April 19, 2024)
Created March 31, 2005, Updated October 12, 2021