Kirkendall void formation in thin-film diffusion couples

Abstract

Transmission electron microscope studies of Sn/Au thin-film couples reveal complexities associated with the Kirkendall effect in thin films. The use of an offset film fabrication technique permitted the identification of two room-temperature interdiffusion mechanisms in Sn/Au: grain-boundary diffusion of Sn into Au, which causes film thinning, and bulk diffusion of Au into Sn, which results in the formation of microscopic Kirkendall voids. The ranges of importance of the two mechanisms were explored by varying the Sn and Au film thicknesses and the grain size. It is pointed out that interdiffusion studies in thin films required careful attention to relative film thicknesses, film geometry, and grain sizes in order to determine the fast-diffusing species and the operative diffusion mechanisms.

Real-Time Investigation of Solid and Liquid State Reactions In Au-Sn/Cu System

“…The diffraction pattern by 0-20 scan shows the presence of Au ans AuSn. This result agrees with the literatures (6,7] which report that only AuSn phase exists at the interfaces in Au-Sn thin film at the room temperature. The x-ray diffraction pattern with low incident angle, however, shows the presence of AuSn in addition to Au and AuSn.…”

Changing the Growth Behavior of a NiSn-Solder Using Gold

“…The solid state diffusion in the Au/Sn system and the reaction of Au and Sn in the solid state has been studied extensively in the literature which concluded that the Au diffuses into Sn via bulk diffusion and Sn diffuses into Au via grain-boundary diffusion. If this occurs in an environment with excess of Sn, AuSn 4 can form [2] [3]. The results of the references were also in accordance with the EDX analysis of the AuSn 4 grains in the as deposited samples, one of which is displayed in Figure 2(a).…”

The Effects of Tin Underlays on the Stability of Gold Thin Films during Isothermal Annealing

“…Some tin and oxygen can be observed on the free gold surface. By using the grain boundary diffusivity of Sn into Au at room temperature (D 2 lo-', cm2/s [12]) one can calculate a diffusion distance [17,181 of tin in gold as much as 3 pm during 30 day storage at room temperature, which is 40 times the present gold film thickness. The thickness of the tin oxide layer on top of the gold film is observed to increase during annealing as shown in Fig.…”