Electron energy-loss spectroscopy study of a multilayered SiO x and SiO x C y film prepared by plasma-enhanced chemical
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Andreas Schulz Institut für Plasmaforschung, Universität Stuttgart, D-70569 Stuttgart, Germany (Received 3 June 2005; accepted 12 September 2005)
A multilayered structure of SiOx and SiOxCy on silicon substrate was prepared by plasma-enhanced chemical vapor deposition from gas mixtures of hexamethyldisiloxane and oxygen. Scanning transmission electron microscopy studies showed that the structure is well defined with distinct layers. The distributions of Si, C, and O were measured via electron energy-loss spectroscopy. We found that the elements C, Si, and O interdiffuse quite differently across the interfaces. The Si–L2,3 energy-loss near-edge structures in the SiOx and SiOxCy layers were different from those of pure Si, SiC, and Si3N4, which all contain a tetrahedral structure unit. Slight variations of the relative ratio of the first two sharp peaks at about 108 and 115 eV were found, which can probably be attributed to C partially substituting O atoms in the Si–O tetrahedral structure.
I. INTRODUCTION
Because of the importance of Si–SiO2 interfaces in metal oxide semiconductor (MOS) devices, the system has been widely investigated.1 So far, several techniques,2,3 such as thermal oxidation at elevated temperature and plasma-assistant oxidation at lower temperature, etc., have been used to form the Si–SiO2 interface for advanced complementary MOS devices. On the other hand, silicon carbide has also received much attention for high-power, high-speed, and high-temperature electronic devices, as it is a potential alternative semiconductor to Si. The growth of SiC on Si can be improved by oxygen-ion implantation directly into SiC.4,5 This normally leads to the formation of SiOxCy in the amorphous layer.4 However, SiOxCy films have so far received less attention. The microstructure of the SiOxCy layer will influence the properties of the devices. It is obvious that exploring the microstructure about SiOxCy films will aid in understanding the Si/SiO2, Si/SiC interfaces, and their diverse applications as well as its own applications in semiconductor devices. In this work, well-defined multilayered SiOx and SiOxCy films on silicon, prepared by plasma-enhanced chemical vapor deposition (PECVD), were intensively studied by scanning transmission a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2006.0073 608
J. Mater. Res., Vol. 21, No. 3, Mar 2006 http://journals.cambridge.org Downloaded: 04 Apr 2015
electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). II. EXPERIMENTAL
The plasma source used for the deposition of single, sandwich and multilayer films is called Duo-Plasmaline (homemade).6 In this source, the plasma is excited in a low-pressure vacuum chamber by microwaves at a frequency of 2.45 GHz. The Duo-Plasmaline produces a linearly extended and axially homogeneous plasma around a quartz tube. For the large-area thin film deposition, a double Plasmaline system was chosen.7 The multilayered film was prepared by the following procedures. After a surface pre-
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