椭偏光谱仪在TiO2薄膜及多层增透膜中的应用

SpectroscopicElipsometryTiO2 Optical Constants SpectroycopictlipsometryCharacterisation of TiO，ThinFilms and Multilayer AntireflectiveCoatings zCeline Marchand -Application Scientist - Thin Film Division UVISELo TiO2 films are extensively studied because of their interesting chemical， electrical and optical prop-erties. TiO2 is a high bandgap semiconductor that is transparent to visible light and has excellent opticaltransmittance. TiO2 has high refractive index and good insulating properties， and as a result it iswidely used as protective layer for very large scale integrated (VLSI) circuits and for manufacture ofoptical elements. Additionally TiO2 films have potential uses for a number of electronic device ap-plications such as dye-sensitized photovoltaic cells as well as antireflective (AR) coatings， gas sensors，electrochromic displays， and planar waveguides. The high dielectric constant of TiO2 allows its con-sideration as an alternative to silicon dioxide for ultrathin gate oxide dielectrics used in memory andlogic devices. Several methods have been used to prepare titania films， and these include chemical vapour deposi-tion (CVD)， pulsed laser deposition， reactive sputtering and sol-gel deposition. The sol-geltechniquehas emerged as one of the most promising techniques as this method produces samples with goodhomogeneity at low cost. To achieve optimum performance it is important to characterise the optical constants and thicknessesof thin TiO2 layers accurately. In this note， we show how the Spectroscopic Ellipsometry (SE)， non-de-structive optical technique is particularly suitable for thin film characterisation. Characterisation of TiO2 Thin Films For this work TiO2 films were prepared using a sol-gel technique， by spin coating on a pre-treated glasssubstrate (CNRS-LIMHP-Universite Paris 13). The work was performed using a Jobin Yvon UVISEL NIR Spectroscopic Phase Modulated Ellipsometer，with an automatic goniometer. To achieve this characterisation both reflection and transmission ellip-sometry were performed. Ellipsometric measurements were collected at an angle of incidence of 70°across the spectral range 310-1700 nm， with spectroscopic transmission data acquired at normal in-cidence. Jobin Yvon DeltaPsi2 (DP2) software allows the measurement and use of multiple data types，and the simultaneous analysis of these two models was achieved by the Bound Multimodel function.The New Amorphous dispersion formula was used to model the refractive index for TiO2. From thesimultaneous analysis of all data， both refractive index and film thicknesses were obtained without am-biguity. Bound Multimodel window of DeltaPsi2 software The New Amorphous dispersion formula is arewriting of original Forouhi-Bloomer formula(Phys. Rev.B， 34，7018 (1986)). Bj(@-Q.)+Cj n=n 160115 HORIBAGROUP The best model comprises of two layers with the top layer being less dense than ithe bottom layer. The top layer is calculated by the addition of void using theEffective Medium Approximation. This work was performed in collaboration with Lamia Znaidi from the CNRS-LIMHP-Universite Paris 13 Characterisation of TiO， in 8-layer Hi-Lo Index Stack The analysis was performed with the UVISEL Visible Ellipsometer across the range 310-830 nm at an incident angle of70°. The best fit model was obtained using a nine-layer model that included a roughness layer at the sample surface. DP2software allows characterisation of these structures using the special Periodic Structure and Correlated Layer functions thatallow modelling of repeating pairs of layers used in MQW or Bragg Reflector structures. Optical constants of TiO2 in Hi-Lo index stack 2.350 0.100 2.300 -0.050 2.250 -0.000 400 500 600 700 800 Wavelength (nm) Conclusion ( The characterisation of TiO2 as a single layer and as an 8-layer dielectric stack was successfully carried out with the UVISEL Spectroscopic Phase Modulo t ed l F lipsometer. Accurate and simultaneous determination of thickness and optical proper- ies have been p erformed i n the NIR/Visible range. Similar analyses h ave been a p plied t o other high-k material such as Ta2O5 / glass， Al2O3/3*{A2O3/a-Si}/ GaAs， SiO2/2*{HfO2/SiO2)/ glass. ) Bibliography："Optical properties of TiO2 Thin Films synthesized by Sol-Gel process"， L.Znaidi，1. Ninova， C. Marchand， J. P. Gaston， V. Blaskov， Journal of Electroceramics (submitted)."Optical properties of polycrystalline and epitaxial anatase and rutile TiO2 thin films by rf magnetron sputtering"， S. Tanemura， L. Miao， P. Jin， K. Kaneko，A. Terai， N. Nabatova-Gabain， Appl. Surf. Sci. 212-213 (2003) 654-660. "Optical characterisation of anatase： a comparative study of the bulk crystal and the polycrystalline thin film"， T.M.R. Viseu， B. Almeida， M. Stchakovsky， B.Drevillon， M.I.C. Ferreira， J.B. Sousa， Thin Solid Films 401 (2001)216-224. France Z.A. de la Vigne aux LoupsUSAJY Germany：+49 (0)89 462317-05， avenue Arago3880 Park AvenueJY Italy： +39 0 25760 305091380 Chilly MazarinEdison， NJ 08820JY Japan： +81 (0)3 3861 8231Tel： +33 (0)1 64 54 13 00Tel：+1-732-494-8660JY UK： +44 (0)20 8204 8142Fax： +33 (0)1 69 74 88 61Fax： +1-732-549-5125JY China： +86 (0)10 6849 2216E-mail： tfd-sales@jobinyvon.frE-mail： info@jobinyvon.comJY Korea： +82 (0)2 576 8650 Explore the futureEMISSION·FLUORESCENCE·FORENSICS·GRATINGS E OEM ·OPIICAL SPECTROSCOPY·RAMAN·THIN FILM