The ellipsometric measurement of refractive indexes for films less than 50 nm thick is of dubious quality due to the significance of the size of random errors relative to the accuracy required to extract reliable index values from the measurements. In this study the various errors are quantitatively assessed as a function of the film thickness, and then compared with experimental data obtained from differently prepared silicon dioxide films on silicon. The new results confirm previous work that shows higher refractive indexes for thinner films. Transmission electron microscopy confirms the results. Graded and discrete layer models are compared.

Single wavelength ellipsometry, although used extensively in the microelectronics field for the measurement of film thicknesses and refractive indexes, does not usually yield reliable refractive indexes for dielectric films less than 50 nm thick due to instrumental errors and software limitations. Addressing this issue, we employ previously developed ellipsometric procedures that enable a reliable assessment of refractive index profiles for a variety of thermally grown and chemically vapor deposited (CVD) dielectric films on Si substrates down to about 10 nm thickness, and we compare the results in terms of the current understanding about the film‐substrate interface. In all cases studied we find that the interfacial region is optically different than the bulk film and that the precise film processing can substantively alter the nature of the interface region.

,,nTIC S UL27 12U 92-20007eroduction in whole or in part is permitted for any purpose of the United States Goverrzmnt.This docment has been approved for public release and sale; its distribution is unlimited. This dwm-nt has been approved for public release and sale, distribution of this dcument is unlimited. REPORT DOCUMENTATION PAGE ABSTRACT (Maximum 200 words)From spectroscopic ellipsometry measurements in the 1.5 to 5.7 eV photon energy range we determined the cciplex dielectric function of thermally gron genranium dioxide in the 1.0 to 6.3 eV range. A Kramers-Kronig consistent dispersion fonmxla utilizing an exponential shaped optical band edge was used in conjunction with both previously published far ultraviolet absorbance data for amorphous GeO 2 and our spectra. These measurements show that C2 for GeO2 can be regarded to bg zero in the range of E 4 5,5 eV, which differs fram a previous report. Using this ne optical results for the investigation of oxide growth, we find Uh GeO2 grows via 0 a parabolic growth law with a growth constant, kp = 1.2 10' m 2 s -L at 550 C. ABSTRACTFrom spectroscopic ellipsometry measurements in the 1.5 to 5.7 eV photon energy range we determined the complex dielectric function of thermally grown Germanium dioxide in the 1.0 to 6.3 eV range. A Kramers-Kronig consistent dispersion formula utilizing an exponential shaped optical band edge was used in conjunction with both previously published far ultraviolet absorbance data for amorphous GeO 2 and our spectra. These measurements show that e2 for GeO 2 can be regarded to be zero in the range of E<5.5 eV, which differs from a previous report. Using this new optical results for the investigation of oxide growth, we find that GeO 2 grows via a parabolic growth law with a growth constant, In 1969 In this paper we report the spectroscopic ellipsometric (SE) characterization of thermally grown germanium oxides on single-crystal germanium substrates in the energy range of 1.5 to 5.7 eV. A novel Kramers-Kronig consistent dispersion formula that is based on the main spectral features of the amorphous GeO 2 far ultraviolet (FUV) absorbance spectrum 4 , and utilizing an exponential shaped optical band edge, precisely fits both our 3 spectra and previously published absorbance data. This procedure is valid in the entire range between hydrogen related absorbance in the near infrared near 1 eV and to about 6.3 eV, were the detailed structure of the UV absorbance must be taken in account.The ellipsometric measurements were carried using a previously described home made rotating analyzer spectroscopic ellipsometer 6 operating in the energy range 1.5 to 5.7 eV.All the measurements were performed at an incidence angle of 70.0". The offsets of polarizer and analyzer were determined for each sample 7 and an optical filter cut off at 350 nm was used for measurements below 2.5 eV.Germanium oxide films were thermally grown on commercially available single crystal (111) germanium substrates. All Ge substrates were subjected to a pre-oxidation cleaning ...