Optical properties and structure of HfO2 thin films grown by high pressure reactive sputtering

Thin films of hafnium oxide (HfO2) have been grown by high pressure reactive sputtering on transparent quartz substrates (UV-grade silica) and silicon wafers. Deposition conditions were adjusted to obtain polycrystalline as well as amorphous films. Optical properties of the films deposited on the silica substrates were investigated by transmittance and reflectance spectroscopy in the ultraviolet, visible and near infrared range. A numerical analysis method that takes into account the different surface roughness of the polycrystalline and amorphous films was applied to calculate the optical constants (refractive index and absorption coefficient). Amorphous films were found to have a higher refractive index and a lower transparency than polycrystalline films. This is attributed to a higher density of the amorphous samples, which was confirmed by atomic density measurements performed by heavy-ion elastic recoil detection analysis. The absorption coefficient gave an excellent fit to the Tauc law (indirect gap), which allowed a band gap value of 5.54 eV to be obtained. The structure of the films (amorphous or polycrystalline) was found to have no significant influence on the nature of the band gap. The Tauc plots also give information about the structure of the films, because the slope of the plot (the Tauc parameter) is related to the degree of order in the bond network. The amorphous samples had a larger value of the Tauc parameter, i.e. more order than the polycrystalline samples. This is indicative of a uniform bond network with percolation of the bond chains, in contrast to the randomly oriented polycrystalline grains separated by grain boundaries.

[1]  Yoshimichi Ohki,et al.  Plasma-enhanced chemical vapor deposition and characterization of high-permittivity hafnium and zirconium silicate films , 2002 .

[2]  I. Mártil,et al.  Compositional analysis of amorphous SiNx: H films by ERDA and infrared spectroscopy , 2000 .

[3]  R. Swanepoel.  Determination of the thickness and optical constants of amorphous silicon , 1983 .

[4]  E. Anastassakis,et al.  Lattice dynamics and light scattering in Hafnia and Zirconia , 1975 .

[5]  P. Ehrhart,et al.  Comparison of precursors for pulsed metal–organic chemical vapor deposition of HfO2 high-K dielectric thin films , 2005 .

[7]  I. Mártil,et al.  Microstructural modifications induced by rapid thermal annealing in plasma deposited SiOxNyHz films , 2003 .

[8]  R. C. Weast.  CRC Handbook of Chemistry and Physics , 1973 .

[9]  K. Ebeling.  Emission and Absorption , 1993, Heat Transfer 2.

[10]  I. Mártil,et al.  Rapid thermally annealed plasma deposited SiNx:H thin films: Application to metal–insulator–semiconductor structures with Si, In0.53Ga0.47As, and InP , 2003 .

[11]  Byoung Hun Lee,et al.  Spectroscopic ellipsometry characterization of high-k dielectric HfO2 thin films and the high-temperature annealing effects on their optical properties , 2002 .

[12]  Hideki Takeuchi,et al.  Observation of bulk HfO2 defects by spectroscopic ellipsometry , 2004 .

[13]  B. Cullity,et al.  Elements of X-ray diffraction , 1957 .

[14]  M. Al-Kuhaili.  Optical properties of hafnium oxide thin films and their application in energy-efficient windows , 2004 .

[15]  Jon-Paul Maria,et al.  Alternative dielectrics to silicon dioxide for memory and logic devices , 2000, Nature.

[16]  J. Aarik,et al.  Optical characterization of HfO2 thin films grown by atomic layer deposition , 2004 .

[17]  T. Matsushita,et al.  Photoemission and Absorption Spectroscopy of Mn2Sb, MnAlGe, Mn2As, Cr2As and Fe2As , 1993 .

[18]  J. Röhrich,et al.  The Berlin time-of-flight ERDA setupe , 1998 .

[19]  Y. Chabal,et al.  Hafnium oxide gate dielectrics grown from an alkoxide precursor: structure and defects , 2004 .

[20]  E. H. Nicollian,et al.  Mos (Metal Oxide Semiconductor) Physics and Technology , 1982 .

[21]  Eduard A. Cartier,et al.  Physical and electrical characterization of Hafnium oxide and Hafnium silicate sputtered films , 2001 .

[22]  Carlone.  Raman spectrum of zirconia-hafnia mixed crystals. , 1992, Physical review. B, Condensed matter.

[23]  M. A. Navacerrada,et al.  Physical properties of high pressure reactively sputtered TiO2 , 2005 .

[24]  I. Mártil,et al.  Optical and structural properties of SiOxNyHz films deposited by electron cyclotron resonance and their correlation with composition , 2003 .

[25]  G. González-Díaz,et al.  Optical analysis of absorbing thin films: application to ternary chalcopyrite semiconductors. , 1992, Applied optics.

[26]  John A. Thornton,et al.  Influence of apparatus geometry and deposition conditions on the structure and topography of thick sputtered coatings , 1974 .

[27]  J. Robertson.  High dielectric constant gate oxides for metal oxide Si transistors , 2006 .

[28]  R. E. Hann,et al.  Monoclinic Crystal Structures of ZrO2 and HfO2 Refined from X‐ray Powder Diffraction Data , 1985 .

[29]  M. Fadel,et al.  A study of some optical properties of hafnium dioxide (HfO2) thin films and their applications , 1998 .

[30]  Byung Jin Cho,et al.  Physical and electrical characterization of HfO2 metal-insulator-metal capacitors for si analog circuit applications , 2003 .

[31]  Wolfgang Eckstein,et al.  Influence of energy reflected from the target on thin film characteristics , 1993 .

[32]  John Robertson,et al.  Defects and hydrogen in amorphous silicon nitride , 1994 .

[33]  Hafnium oxide thin films deposited by high pressure reactive sputtering in atmosphere formed with different Ar/O2 ratios , 2006 .

[34]  David Vanderbilt,et al.  First-principles study of structural, vibrational, and lattice dielectric properties of hafnium oxide , 2002 .

[35]  Douglas A. Buchanan,et al.  Scaling the gate dielectric: Materials, integration, and reliability , 1999, IBM J. Res. Dev..

[36]  J. Robertson.  Band offsets of wide-band-gap oxides and implications for future electronic devices , 2000 .

[37]  Eduard A. Cartier,et al.  Materials characterization of ZrO2–SiO2 and HfO2–SiO2 binary oxides deposited by chemical solution deposition , 2001 .

[38]  R. Wallace,et al.  High-κ gate dielectrics: Current status and materials properties considerations , 2001 .

[39]  Michael P Lesser,et al.  Antireflection Coatings For Silicon Charge-Coupled Devices , 1987 .

[40]  I. Mártil,et al.  Compositional analysis of polycrystalline hafnium oxide thin films by heavy-ion elastic recoil detection analysis , 2006 .

[41]  Á. Prado.  Composition and optical properties of silicon oxynitride films deposited by electron cyclotron resonance , 2002 .

[42]  Bradshaw,et al.  Electronic structure of stoichiometric and Ar+-bombarded ZrO2 determined by resonant photoemission. , 1995, Physical review. B, Condensed matter.

[43]  R. García-Molina,et al.  Radial profile of energetic particles bombarding the substrate in a glow discharge , 1999 .

[44]  Germán González-Díaz,et al.  Molecular models and activation energies for bonding rearrangement in plasma-deposited a − SiN x : H dielectric thin films treated by rapid thermal annealing , 2001 .

[45]  J. Malherbe,et al.  Thin Solid Films , 2008 .

[46]  C. Jia,et al.  Low‐resistivity epitaxial YBa2Cu3O7 thin films with improved microstructure and reduced microwave losses , 1992 .

[47]  I. Mártil,et al.  Rapid thermal annealing effects on the electrical behavior of plasma oxidized silicon/silicon nitride stacks gate insulators , 2003 .

[48]  K. Mittal,et al.  Optical and dielectric constants of hafnium and its anodic oxide films , 1975 .

[49]  Thermally induced changes in the optical properties of SiNx:H films deposited by the electron cyclotron resonance plasma method , 1999 .