Texture and Resistivity of Cu and Dilute Cu Alloy Films
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TEXTURE AND RESISTIVITY OF Cu and DILUTE Cu ALLOY FILMS K. Barmak, A. Gungor, A. D. Rollett, C. Cabral, Jr.1, J. M. E. Harper1 Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 1 IBM T. J. Watson Research Center, P. O. Box 218, Yorktown Heights, NY 10598
ABSTRACT Annealing of dilute binary Cu(Ti), Cu(In), Cu(Al), Cu(Sn), Cu(Mg), Cu(Nb), Cu(B), Cu(Co) and Cu(Ag) alloy films resulted in the strongest fiber texture for Cu(Ti) and the lowest resistivity for Cu(Ag). The behavior of the alloy films was compared and contrasted with that for a pure evaporated Cu film. Electron beam evaporated films with compositions in the range of 2.0-4.2 at% and thicknesses in the range of 420-560 nm were annealed at 400˚C for 5 hours. Two different approaches were used to derive volume fractions of texture components, namely fiber plots and orientation distributions. It is argued that for polytextured films such as the copper alloys studied here, orientation distributions derived from pole figures provide the most reliable basis for quantitative characterization. INTRODUCTION The need to reduce delays in integrated circuits prompted the replacement of Al(Cu) with Cu in the 1990’s. However, as line widths approach 100 nm, the addition of alloying elements to tailor the grain size and crystallographic orientation (i.e., texture), and thus the reliability and functionality, of Cu interconnections may become necessary. In previous work, we investigated the impact of alloying elements on the decomposition and electrical resistivity of a group of dilute binary, non-compound forming Cu alloy films annealed at a constant heating rate up to 950˚C [1]. In this work, we address the evolution of texture and resistivity in a series of nine Cu alloy films that are annealed isothermally at 400˚C. By way of connection to our previous work, five of the alloys have been chosen from among compound forming binary Cu systems and four have been chosen from among non-compound forming systems. The five compound forming systems are Cu(Ti), Cu(In), Cu(Al), Cu(Sn) and Cu(Mg), and the four non-compound forming systems are Cu(Nb) Cu(B), Cu(Co) and Cu(Ag). We compare and contrast the behavior of the alloy films with that for pure Cu. In addition, we discuss the advantages and disadvantages of two different x-ray based methods commonly used in the study of texture, i.e., in the determination of the spatial distribution of the crystal axes in a polycrystalline aggregate, and how to choose the best method for a given film type. EXPERIMENTAL Pure Cu and dilute binary Cu alloy films were electron beam evaporated onto thermally oxidized silicon wafers. The composition and thickness of the films are listed in Table I. X-ray diffraction experiments were conducted using Cu Kα radiation in a Rigaku θ-2θ powder diffractometer with a curved graphite monochromator. These patterns were used to give a J3.1.1 Downloaded from https://www.cambridge.org/core. Iowa State University Library, on 11 Jan 2019 at 08:20:21, subject to the Cambr
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