Enhanced [111] Preferred Orientation of Ag Thin Film on Amorphous SiO 2 by Cu Addition
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0990-B08-06
Enhanced [111] Preferred Orientation of Ag Thin Film on Amorphous SiO2 by Cu Addition Yeongseok Zoo, Hauk Han, and Terry L. Alford School of Materials, Arizona State University, tempe, AZ, 85287-8706 ABSTRACT Small amounts of copper were added to enhance the adhesion and minimize agglomeration of Ag thin films on SiO2 substrates. Comparison of texture profiles between Ag and Ag(Cu) thin films showed that Cu additions enhanced (111) texture in Ag thin films. For the case of Ag film, (111) texture was enhanced mainly by recrystallization of amorphous regions during annealing. In addition to the recrystallization, (111) texture enhancement in Ag(Cu) film attributes to the dissociation of grains with other crystallographic orientations. INTRODUCTION Silver has been recognized as a promising candidate in ultra-large scale integrate (ULSI) application in that it has the lowest bulk electrical resistivity of all pure metals and higher electromigration resistance than other interconnect materials [1]. However, the agglomeration during the thermal processing limits the stability of Ag thin films and compromises the filmís reliability. Kim et al. [2] reported that the agglomeration of Ag thin film is significantly reduced by the addition of Al. Contrary to this positive effect, Al addition decreased the preferred orientation of Ag film which is a main factor that influences the electromigration resistance [2]. In this study, the texture evolution of Ag thin films was investigated as a function of annealing temperature and compared with the texture of Ag(Cu) alloy films. Under the same annealing conditions, the Ag(Cu) film showed an (111) texture enhancement due to the presence of Cu. Based on these results, we discussed how Cu promotes [111] preferred orientation of Ag thin films. EXPERIMENTAL DETAILS Silver and silver-copper thin films were deposited on thermally grown SiO2 using electron-beam evaporation. The samples were annealed in vacuum for 1 hour at various temperatures in order to investigate texture changes as a function of annealing temperature. The texture evolution of Ag and Ag(Cu) thin films was investigated by Bragg-Brentano configuration (θ-2θ geometry) and pole figure analyses. In addition, glancing angle X-ray diffraction analysis was used to investigate thermal behavior of Ag grains tilted from the surface. The glancing angle geometry has the incident beam at a low angle (i.e., 1o) to maximize the X-ray interaction
volume in the thin film while the detector moves within a desired 2θ range. DISCUSSION Figure 1 shows (111) relative intensities of Ag and Ag(Cu) films. The (111) relative intensities of both Ag and Ag(Cu) thin films increase with increasing anneal temperature increases. Typically, FCC metals like Ag, Al, and Cu show [111] preferred orientation because the (111) plane has the highest packing density [3]. However, the preferred orientation of asdeposited thin films strongly depends on the film thickness, deposition conditions, and substrate types. Another important point from figure
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