Laser Assisted Molecular Beam Deposition of Thin Films for Gate Dielectrics Applications
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LASER ASSISTED MOLECULAR BEAM DEPOSITION OF THIN FILMS FOR GATE DIELECTRICS APPLICATIONS Robert L. DeLeon, James F. Garvey, and Gary S. Tompa, AMBP Tech Corporation, Amherst, NY 14228 and Richard Moore and Harry Efstathiadis School of NanoSciences and NanoEngineering, The University at Albany-SUNY, Albany, NY 12203. ABSTRACT High dielectric constant (k), the thermal stability and the chemical stability with respect to reaction with silicon of hafnium oxide (HfO2), and zirconium oxide (ZrO2) places them among the leading candidates for an alternative gate dielectric material. High dielectric constant HfO2 and ZrO2 thin films have successfully been deposited on silicon substrates at a temperature of 27 °C by Laser Assisted Molecular Beam Deposition (LAMBD). The LAMBD process is related to conventional Pulsed Laser Deposition (PLD). In the PLD process, the ablation plume impinges directly upon the substrate to deposit the thin film, whereas in the LAMBD process, the ablation material is expanded within a concurrently pulsed stream of a reactive gas. The gas pulse serves both to create the desired material and to transport the material to the substrate for deposition of the thin film. One advantage of the LAMBD process is that a chemically reactive carrier gas can be selected to produce the desired chemical products. Depositions yielded 35 nm to 135 nm thick HfO2, and ZrO2 films. Structural and chemical characterization of the films were performed by Auger electron spectroscopy (AES), Rutherford back-scattering (RBS), scanning electron microscopy (SEM), and x-ray diffraction (XRD). Film surface was investigated by atomic force microscopy (AFM) while optical characterization was also performed by means of spectroscopic ellipsometry (SE). Within the process window investigated, the film Hf/O and Zr/O ratios was found to be in the range 0.6 to 1.2. The as deposited films were amorphous with refraction index (RI) at 623 nm wavelength films in the range of 1.22 to 1.27 for the HfO2 and in the range of 1.23 to 1.19 for the ZrO2 films. INTRODUCTION The scaling of integrated-circuit (IC) technology continues to be a critical for the Sibased microelectronics industry in order to increase functionality and fuel market expansion. The 2001 International Technology Roadmap for Semiconductors (ITRS) points to several challenges for the semiconductor industry to meet, and many of these challenges require the development of new materials and their introduction to the manufacturing process [1]. In this respect, the successful development of new high dielectric constant (k) thin films for advanced complementary metal-oxide semiconductor (CMOS) devices to replace silicon dioxide requires the fundamental understanding of the relationship between the physical and the electrical properties of the high-k gate dielectric and substrate and gate interfaces. This presents an opportunity for the materials science community, as the effort requires substantial research and development in materials science and, more important, materials inte
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