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The Structure of Plasma-Deposited and Annealed Pseudo-Binary ZrO2-SiO2 Alloys G. Rayner Jr., R. Therrien, and G. Lucovsky Departments of Physics, Electrical and Computer Engineering, and Materials Science and Engineering North Carolina State University, Raleigh, NC 27695-8202, USA ABSTRACT The internal structures of various (ZrO2)x(SiO2)1-x alloys (x ≤ 0.5) were investigated. A remote plasma enhanced-metal organic chemical vapor deposition (RPEMOCVD) process was used to deposit films with varying alloy composition on Si(100) substrates. This study indicates that for the glassy silicate phase, g-ZrSiO4, a glass transition temperature, Tg, exists between 800°C and 900°C at which phase separation into the end-member components, SiO2 and ZrO2, occurs. INTRODUCTION Pseudo-binary (ZrO2)x(SiO2)1-x alloys are currently being considered as a high-k dielectric for microelectronic applications [1,2]. Due to post-deposition processing, one important issue is thermal stability of the internal structure. This paper identifies some limitations of these alloys for high-k dielectric applications. These limitations are associated with the thermal stability of the stoichiometric silicate phase, ZrSiO4. EXPERIMENTAL Films were deposited by a RPE-MOCVD process described elsewhere [1] onto Si(100) substrates. Film composition was determined by Rutherford backscattering spectrometry (RBS). Alloy internal structure, as-deposited and following subsequent annealing, was characterized by X-ray diffraction (XRD) and infrared (IR) absorption spectroscopy. Post deposition 60s anneals at 600°C, 700°C, 800°C, and 900°C were performed ex-situ on each sample in an inert argon ambient using an AG Minipulse 310 RTA unit. XRD measurements were made using a Bruker x-ray diffractometer with a beryllium area detector centered at the following 2θ positions: 25° and 50°. IR absorption measurements in the mid-IR regime (4000-400cm-1) were carried out on a Nicolet Magna-FTIR 750 spectrometer. Due to the relatively slow deposition rate (~ 4 Å/min), films were deposited for eight hours to ensure that the thickness was sufficient for good IR absorption sensitivity. RESULTS AND DISCUSSION A portion of the equilibrium compositional phase diagram [3] for the pseudobinary ZrO2-SiO2 system is presented in Fig. 1. This figure illustrates only the chemical phase of each component and not any particular structural phase. The phase diagram, for temperatures below ~1600°C, can be divided into two regions based on chemical

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composition: 1) a SiO2-rich region (0 ≤ x < 0.5) from SiO2 to the silicate phase, ZrSiO4, and 2) a ZrO2-rich region (0.5 < x ≤ 1) from the silicate phase to the end-member, ZrO2. Above ~1600°C, ZrSiO4 phase separates into the end-member components, SiO2 and ZrO2 (ZrSiO4 → ZrO2 + SiO2). It must be emphasized that this transition temperature corresponds to the crystalline silicate phase, c-ZrSiO4. Included in this diagram is the glass transition temperature, Tg, which corresponds to the temperature at which the glassy silicate phase, g-ZrSiO4, so