Microstructure and mechanical properties of sputter-deposited Cu1−x Ta x alloys

Abstract

The microstructures and mechanical properties of a family of sputter-deposited Cu 1Ϫx Ta x (0 Ͻ x Ͻ 0.18) alloys have been investigated. The as-deposited microstructures for all film compositions consisted of a polycrystalline, face-centered-cubic (fcc) Cu matrix, with varying levels of Ta in solid solution, plus a very high density of discrete, 1 to 3 nm, fcc Ta particles. Decreased deposition temperature (Ϫ120 ЊC vs 100 ЊC) increased the level of Ta in solid solution. After annealing (900 ЊC for 1 hour) the as-deposited 6 at. pct Ta films, the Cu matrix grains remained submicron and the Ta particles remained fcc with no apparent particle coarsening. Additionally, the fcc Ta particles were found before and after annealing to be oriented identically with the Cu matrix and aligned on {111} and {100} habit planes. Annealing 17 at. pct Ta films at 900 ЊC for 1 hour resulted in the formation of body-centered-cubic (bcc) Ta particles (Ͼ50-nm diameter) in addition to the much smaller fcc Ta particles. Annealing the low and high Ta composition films at 900 ЊC for as long as 100 hours produced no observed change in either the Cu matrix grain size or the size and distribution of the fcc and bcc Ta particles. Microhardness and nanoindentation mechanical property evaluations of bulk hot-pressed materials indicated that the high strengths of the composites were unchanged, even after annealing for 100 hours at 900 ЊC.

Atomic size effects on the hardness of RF sputtered Al–Cu(rich) thin films

“…It increases regularly with the aluminium concentration and will reach a maximum over the concentration 33.36 at.%Al. This evolution is very close to that already observed for sputtered thin films Cu-Ta [5]. The extrapolation of the microhardness of sputtered pure copper gives an approximate value of 5000 MPa, it exceeds of about 3500 MPa to that of bulk pure copper measured under the same conditions ( Table 4).…”

“…Another equation was found for Cu solid solution in sputtered Al-Cu prepared almost in the same conditions [4]: a (nm)=0.3615+2.4 Â 10 À4 x, the apparition of the second phase g-Al 4 Cu 9 is announced for 25 at.%Cu. A similar evolution is found for copper solid solution in Cu-0-18 at.%Ta thin films deposited at À120 C [5] and has the form: a (nm)=0.3612+1.8 Â 10 À4 y, where y is Ta atoms concentration (at.%Ta). But fine particles of Ta were found in dilute deposited Cu-Ta films.…”

“…On the other hand, the microstructures of CuTa deposits consisted of polycrystalline (FCC)Cu matrix with varying levels of Ta particles. The addition of Ta atoms in a Cu matrix increases its intrinsic resistance [5].…”

Characterization of Microstructure, Interfacial Reaction and Diffusion of Immiscible Cu(Ta) Alloy Thin Film on SiO[sub 2] at Elevated Temperature

“…Wang et al reported that the microstructure of Cu-Ta alloy film, 12 m thick, remained submicrometer grain size and the Ta particles precipitated to grain boundary after annealing at 900°C. 14 However, as an interconnect material, there is no detailed literature regarding the interfacial reaction and diffusion of Cu-Ta alloy films ͓referred to as Cu͑Ta͒ hereafter͔ with its neighboring materials. The diffusion of Cu into SiO 2 may cause degradation of devices at high temperature or high voltage.…”

Study of solid-solution hardening in binary aluminium-based alloys

“…• C [20]. This parameter increases with Ta composition in the films where the structure is two phases as a copper matrix in which are distributed fine particles of tantalum.…”