Comparison of High-Purity-Ozone Oxidation on Si(111) and Si(100)
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A. KUROKAWA *, S. ICHIMURA *, D. W. MOON ** *Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba 305, JAPAN **Korea Research Institute of Standards and Science, Taejon, KOREA ABSTRACT The oxidation of Si(l 11) and Si(100) surfaces with the high-purity ozone(more than 98 mole %) was investigated with X-ray photoelectron spectroscopy (XPS). Thin oxide less than 3nm thickens was formed in an experimental chamber and the results showed that ozone oxidizes the (111) surface faster than (100) surface. Ozone does not show the temperature dependence on oxidation within the temperature range of 250-500 degree C for both (111) and (100) surfaces. Ozone proceeds the oxide formation at 700 degree C where oxygen does not proceed oxide formation rapidly. INTRODUCTION The continuous scaling down of semiconductor device dimensions demands the thickness of silicon oxide to be several nm in the near future. It also demands that oxide should be electrically good insulator at that thickness. We have investigated the oxidation with high purity-ozone since ozone is highly active oxidant rather than oxygen. The oxide layer is usually grown with molecular oxygen at high temperature. A more reactive species than molecular oxygen may possibly form an oxide layer with good quality at lower oxidation temperature. To investigate the ozone oxidation mechanism we studied oxidation on two surface orientations of Si(1 11) and Si(100). The Si(1 11) surface is known to be prepared in atomically flat with chemical treatment and the oxide grows in layer-by-layer mode. We previously showed that ozone forms oxide rapidly and makes less suboxide at room temperature on Si(11)[1]. The Si(100) is also important orientation since it is widely used in semiconductor industry. In this report the ozone oxidation on Si(100) and Si(1 11) surface was investigated with Xray photoelectron spectroscopy (XPS). The ozone oxidation was compared with oxygen oxidation at high temperature up to 700 degree C. We used an experimental chamber instead of a industry standard furnace to form oxide with the high purity ozone ( more than 80 mol% ) in order to study the ozone oxidation. EXPERIMENT Figure 1 shows a schematic view of experimental setup. The sample were P-doped Si(1 11) with resistivity of lohm cm and P-doped Si(100) with resistivity of 5 ohm cm. The sample was set in an analysis chamber after ultrasonic cleaning in acetone and ethanol. It was annealed at 500 degree C for 3 hours and thermally flashed at 1050 degree C. After thermal flashing the surface was confirmed to be clean with XPS. The XPS analysis was done using Mg Ka and Al Ka X-ray source and a double-pass cylindrical mirror analyzer (CMA). The pass energy of photoelectrons through CMA was set at 100 eV for survey spectra and at 50 eV for Ols and Si2p observations.
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Mat. Res. Soc. Symp. Proc. Vol. 477 01997 Materials Research Society
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XPS Analyzer Experimental Chamber
Cold Vessel Ozone Jet Generator
Fig. 1 Schematic view of experimental setup. The
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