Spectroscopic ellipsometry studies of very thin thermally grown SiO2 films: Influence of oxidation procedure on oxide quality and stress

Abstract

The qualitative and structural modifications of very thin SiO2 films with thicknesses between 80 and 500 Å, caused by the oxidation procedure, were studied with spectroscopic ellipsometry (SE). Analysis of the experimental dielectric function obtained by SE provides the structural characteristics and the thickness of the oxide in fairly good agreement with electron microscopy results in cross-sectional geometry. The calculated voids volume fraction was found to drop below 3% (2%) for oxides thicker than 250 (400) Å grown at 900 (1000) °C. The densification of thermal oxides grown at low oxidation temperature predicted by Fourier transform infrared is discussed and compared to the SE results, whereas a relation between the final oxidation time and the viscoelastic relaxation time was found. Furthermore, it is shown that in situ SE can be used to monitor the process of oxide removal with very low-energy Ar+ ions and to control the conditions in order to avoid oxide and Si substrate damage. It is found that Ar+ ions with energy of about 10 eV are required to avoid oxide damage and Si substrate amorphization at a depth below 6 Å. The latter finding is also corroborated by atomic force microscopy images obtained from Si substrates after oxide etching. Finally, the influence of oxide thickness and the oxidation procedure on the E1 structure of c-Si was studied and from the results the stress applied by the oxide on the Si substrate was determined. From this study it was found that the stress depends strongly on the oxidation duration as well as on the oxidation procedure and the type of Si substrate and is minimized at an oxidation temperature 900 °C for oxidation duration longer than 70 min.

Analysis of Organic Films and Interfacial Layers by Infrared Spectroscopic Ellipsometry

“…Defined adsorption geometries and electronic properties are perturbed when oxidation of the silicon surface occurs either during the preparation or afterwards through and underneath the grafted layer. It is therefore an important finding that IRSE allows the study of the hydrogen termination 6,98 and oxidation [1][2][3][4][5][6][7][8][9][10][11] at the same time. The observation of different vibrational modes from (SiH x ) stretching vibrations in the infrared ellipsometric parameters gives direct access to the morphology of the silicon surface.…”

“…IRSE has been successfully applied to the study of inorganic materials and films as, for * E-mail: hinrichs@ansci.de. example, SiO 2 , [1][2][3][4][5][6][7][8][9][10][11] ferroelectric films of SrTiO 3 , 12 films of AlN, 13 ZnO, 14 InN, 15 ITO, 16 GaAs, 17 CN, 18 GaN, 19 oxidized Si 3 N 4 , 20 SiC, 21,22 CO/Cu, 23 PbZrTi, 24 BN, 25,26 AlGaN, 27 AlInN, 28 amorphous carbon, 29,30 silicon, [31][32][33] and metallic island films. 34,35 Some of these inorganic materials could be of great technological relevance in components of functional hybrid materials, biosensors, microelectronic devices, or solar cells.…”

Infrared ellipsometric study on the initial stages of oxide growth on Si(001)

“…Ellipsometry in the UV-VIS spectral range has evolved into a standard tool to determine the thickness of thin oxide layers [22,23]. With the advent of commercially available infrared ellipsometers, infrared spectroscopic ellipsometry has also been increasingly used [24][25][26][27][28] to study thin silicon oxide films. In this work we show that the sensitivity of IR-ellipsometry allows one to study even the very initial steps of oxide growth in a single reflection geometry.…”

Monolayer-Controlled Deposition of Silicon Oxide Films on Gold, Silicon, and Mica Substrates by Room-Temperature Adsorption and Oxidation of Alkylsiloxane Monolayers

“…Repeated application of this A−B reaction cycle resulted in a strictly linear growth of the oxide film with an increment of 2.7 Å per cycle . Compared to other growth methods for silicon oxide films (thermal oxidation, chemical vapor deposition (CVD), sequential atomic layer growth based on alternate adsorption of SiCl 4 and H 2 O monolayers from the gas phase, photochemical decomposition of organosiloxane films), the process described in Scheme has several advantages: First, the entire growth takes place at room temperature, whereby unwanted diffusion and redistribution of dopants in the substrate are largely avoided. Second, densely packed alkylsiloxane monolayers can be adsorbed from suitable precursor solutions onto substrates of arbitrary size and shape, in particular on structured surfaces with high aspect ratios or on inner surfaces of porous substrate materials .…”