Influence of Substrate Temperature During Sputter Deposition on the Subsequent Formation of Titanium Disilicide
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Influence of Substrate Temperature During Sputter Deposition on the Subsequent Formation of Titanium Disilicide A. S. Özcan and K. F. Ludwig, Jr. Boston University, Physics Department, Boston, MA 02215, C. Cabral, Jr., C. Lavoie, J. M. E. Harper IBM T.J. Watson Research Center, Yorktown Heights, NY 10598 ABSTRACT We examine how the substrate temperature during Ti film sputter deposition influences the subsequent texture formation in TiSi2 thin films. Titanium films of 32 nm thickness were sputtered onto Si(001) at elevated substrate temperatures varying between 100 °C and 900 °C. After the depositions, in situ x-ray diffraction (XRD) measurements were performed to study the thin film reactions in real time, as the samples were annealed. The XRD results show that the substrate temperature significantly influences the texture of the initial Ti film as well as the texture of the resulting C54-phase TiSi2. The preferred Ti orientation gradually changes from (002) to (101) fiber texture as the deposition temperature increases up to 500 °C. Films deposited at 600 °C transformed into the C49 phase during deposition while films deposited at 700 °C and higher temperatures transformed into the C54 phase during deposition. The series of deposited films was annealed up to 1000 °C in He to complete the C54 phase formation while monitoring the texture evolution in situ using a position sensitive x-ray detector. The XRD results show that the final C54 phase texture changes from a dominant (311) orientation normal to the substrate to a (010) orientation for substrate temperatures between 600 °C and 700 °C. The C49-C54 phase transformation temperature is also lowered for these deposition temperatures. Ex situ pole figure analysis of the film deposited at 700 °C confirms the dominant C54 (010) texture and shows an in-plane orientation with C54 [001] || Si [ 1 10 ]. For substrate temperatures between 800 °C and 900 °C, the C54 texture changes dramatically. In this case, θ 2θ scans do not show a preferred C54 orientation, but pole figure analysis indicates weak inplane orientations. INTRODUCTION Titanium disilicide (TiSi2) has been widely used as a contact electrode in Si ultra-large-scale integrated (ULSI) circuits [1,2]. It exists in two polymorphs, with crystallographic designations C49 and C54. Although the technologically desired C54 phase is the equilibrium structure of the disilicide, under most conditions the C49 phase forms first. The C54 phase transformation is nucleation controlled and because of the small energy difference between the C49 and C54 phases the transformation can be difficult, especially in submicron structures. In order to enhance the C54 phase transformation, various methods have been investigated including the addition of a refractory metal into the Ti film [3], pre-amorphization of the Si prior to deposition [4] and change of Ti sputter deposition conditions [5]. In this study we examine the effects of substrate temperature during sputter deposition on the subsequent formation of TiSi2. Particular a
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