Texture Evolution and Stress in Silver Thin Films on Different Substrates Using X-ray Diffraction
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0990-B08-07
Texture Evolution and Stress in Silver Thin Films on Different Substrates Using X-ray Diffraction Yeongseok Zoo, and Terry L. Alford School of Materials, Arizona State University, tempe, AZ, 85287-8706 ABSTRACT Substrate surface roughness effects on Ag film texture were investigated using pole figure analysis. X-ray diffraction results confirmed that Ag thin films on smooth SiO2 substrates had strong {111} texture when compared with Ag films on polyethylene naphthalate (PEN). It was noted that the difference of strain energy density (∆Eε) in Ag film on PEN (0.039 MPa) was almost 5 times greater than that on SiO2 (0.0084 MPa). The comparison between surface and strain energies revealed that the {111} texture of Ag thin film on SiO2 was explained by minimization of the surface energy and the weaker {111} texture of Ag on PEN was a result of reduced diffusion length of Ag adatoms on the rough PEN surface. INTRODUCTION As the dimensions of electronic devices have decreased with increasing packing density, the thickness of metal layers continues to decrease. The decrease in layer thicknesses changes their electrical properties as well as microstructures. Research has shown that the properties of thin films can be different from the properties of bulk materials and their microstructures are greatly influenced by the underlying substrates [1]. On an amorphous substrate, it is more probable that nuclei will have random orientations. Even though nuclei are randomly oriented, the final structure/orientation of thin films on amorphous substrates is not necessarily identical to the structure/orientation of the initially formed nuclei. Many factors control the orientations of thin films, e.g., adatom mobility [2], deposition rate [3], and thickness of thin film [4]. Previous findings suggest that the competition between surface and strain energies is the main factor that controls the preferred orientation [5]. However, recent studies suggest that the strain energy is not the dominant factor that controls the preferred orientation [6,7]. To address the discrepancy presented above, this study will show how strain energy and substrate surface roughness influence the preferred orientation on amorphous substrates. The preferred orientations and intrinsic stresses of thin films deposited on substrates with different surface roughness are compared using X-ray diffraction (XRD) analyses. On the basis of these results, growth mechanisms of thin films on different surface roughness of amorphous substrates are also discussed.
EXPERIMENTAL DETAILS Electron-beam evaporation was used to deposit Ag onto thermally grown SiO2 and cleaned PEN. Silver layers of the same thickness (200 nm) were deposited to remove the thickness effect. The textures of Ag thin films were investigated by pole figure analysis. In this study, (111) and (200) planes of Ag thin films were chosen to monitor the texture evolution. The strain in the silver thin films was obtained by the sin2ψ technique [8]. The strain was measured by monitoring correlated wit
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