Quantitative Depth Profiles of Vacancy Cluster Defects Produced by MeV Ion Implantation in Si: Species and dose Dependen
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Quantitative Measurement of Interstitial Flux and Surface Super-saturation during Oxidation of Silicon M. S. Carroll a), J. C. Sturm Department of Electrical Engineering, Princeton University, Princeton, NJ 08544 Abstract During the oxidation of silicon, interstitials are generated at the oxidizing surface and diffuse into the silicon. Boron diffusion was used to map the local interstitial super-saturation, the ratio of interstitial concentration to the equilibrium concentration of interstitials I/I*, versus depth above buried Si0.795Ge0.2C0.005 layers during oxidation. The average interstitial supersaturation at the silicon surface, extrapolated from the depth profiles, is measured as, ~24 and ~11.5 for 750°C and 850°C respectively. Using the measured interstitial concentration at the surface, the silicon interstitial injection into the silicon is calculated for oxidation at 750°C and 850°C. Finally, it is found that the surface boundary condition remains fixed over an interstitial injection rate ranging over 4 orders of magnitude. Introduction Recent reports indicate that the introduction of carbon in silicon can suppress the local interstitial concentration and effectively sink interstitials generated either by ion implantation or oxidation [1,2]. In this paper, we describe the use of this property of substitutional carbon in Si0.795Ge0.2C0.005 layers to experimentally determine the profile of interstitial atoms during oxidation of silicon. Combining this with previous measurements of the interstitial transport product allows us to determine the number of interstitials injected into the silicon during oxidation at 750°C and 850°C. Experiment & Discussion Test structures were grown to measure the local boron diffusivity throughout the surface region of samples containing zero (sample A), one (sample B), or two (sample C) buried Si0.795Ge0.2C0.005. The test structures were grown epitaxially using rapid thermal chemical vapor deposition (RTCVD) at temperatures between 600°C and 750°C using dichlorosilane, germane, and methylsilane as the silicon, germanium and carbon sources respectively [3]. Each of the three test structures were grown on top of p-type Czochralski (CZ) (100) silicon wafers. The three different test structures were grown with four 25 nm thick boron marker layers that had peak concentrations of 4-9x1018 cm-3 centered below the surface at 150, 450, 600, and 900 nm depths. Sample B was grown with one 20 nm thick Si0.795Ge0.2C0.005 layer between the boron layers centered at 675 nm below the surface; and sample C was grown with two 20 nm thick Si0.795Ge0.2C0.005 layers centered at 300, and 675 nm below the surface. All asgrown boron concentration profiles are shown in figures 1a, b, and c, and the location of the Si0.795Ge0.2C0.005 layers are indicated by the carbon concentration profiles. Depths of the boron layers differed from the nominal values, unintentionally, as much as 15% sample to sample.
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All test structures were cleaved and annealed in oxygen or nitrogen ambient for various times be
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