Characterization of Ion Implanted Silicon by Spectroscopic Ellipsometry and Cross Section Transmission Electron Microsco
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CHARACTERIZATION OF ION IMPLANTED SILICON BY SPECTROSCOPIC ELLIPSOMETRY AND CROSS SECTION TRANSMISSION ELECTRON MICROSCOPY
P. J. McMARR, K. VEDAM AND J. NARAYAN* Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802 and *Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37380
ABSTRACT This paper deals with the application of spectroscopic ellipsometry (SE) and cross-section transmission electron microscopy (XTEM), to the characterization of damaged surface layers in ion implanted Si single crystal. Si samples of 2-6Q-cm resistivity and orientation were implanted with 28Si+ ions in the dose range of 16 16 2 1.0 x10 - 1.5 x10 ions/cm using ion energies of 100 and 200 keV. Ion current densities were varied from 2 6, to 200 IA/cm . Depth profiles of the implanted samples were evaluated from the spectroscopic ellipsometry data. These calculated profiles were compared with the TEM micrographs of the cross sections of the samples. Excellent agreement is obtained between the two characterization techniques. The characteristics of the depth profiles of the samples, as established by the two techniques, is shown to be the result of annealing occuring during implantation
INTRODUCTION It is well known that the surface layers of ion implanted specimens are highly damaged during the ion implantation process. The depth profile and the degree of damage at various depths from the surface are very strongly dependent on a number of parameters such as the type and the energy of the impinging ions, total dose as well as the dose rate, the orientation and the temperature of the substrate during implanation, etc. In fact, the degree of damage in the implanted region can vary over the entire range -- from total amorphization, to dislocation tangles, to a region totally free of damage. The depth profile of such a damaged region is usually obtained by various techniques such as RBS, ion channelling, XTEM, etc. The present paper shows that spectroscoric ellipsometry is another powerful technique that can yield this information in a quantitative and nondestructive fashion and can also be used as an in-situ technique in most situations. The application of conventional null ellipsometry, for the characterization of damaged surface layers in ion implanted semiconductors is well documented [1]. Good comparisons between the results of these null ellipsometry measurements and RBS, ion channelling, as well as other techniques, have been made 12,3). The advantages of a spectroscopic ellipsometry over that of a single wavelength null system are discussed in references [4-8]. In general, the spectroscopic capability adds the ability to characterize the depth profile of the material, utilizing the fact that the optical penetration (nd hence the region where the reflection takes place) is strongly wavelength dependent. In particular in the case of Si, the high energy regions of the spectra principally contain information about the surface regions, while the low energy regions (X
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