Investigation of Light Initiated Oxidation of Hydrogen Passivated Silicon Surfaces: Hx-Si(100) and H-Si(111)(1X1)
- PDF / 104,521 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 25 Downloads / 152 Views
Investigation of Light Initiated Oxidation of Hydrogen Passivated Silicon Surfaces: HxSi(100) and H-Si(111)(1X1) Kathleen A. Morse Department of Materials Science and Engineering, Stanford University Stanford, CA 94305-2205 Piero Pianetta Department of Electrical Engineering, Stanford University Stanford, CA 94305-2205 ABSTRACT There are factors present in cleanroom air that may lead to contamination prior to processing. These factors need to be better understood in order to meet tomorrow’s requirement for atomically clean surfaces prior to gate oxidation. This paper identifies the conditions that initiate room temperature oxidation of fluoride prepared hydrogen passivated silicon surfaces by using X-ray Photoelectron Spectroscopy (XPS). Possible oxidation factors investigated include lighting conditions and ambient gases. Both Hx-Si(100) and H-Si(111)(1X1) surfaces do not oxidize in dark conditions and in 450nm wavelength lighting conditions for both humid and dry air ambients. These surfaces do oxidize in dry air and humid air when the surface is exposed to shorter wavelengths of light. Wavelength dependence for oxidation on both surfaces is confirmed. In addition, the level of oxidation observed depends on the surface orientation in humid air but not in dry air. INTRODUCTION As the ULSI industry continues the trend of decreased power and of decreased dimensions, the requirements for contamination free, atomically clean silicon surfaces prior to gate oxidation become increasingly more stringent. The 1999 National Technology Roadmap projects that less than 3X1012 carbon atoms per cm2 (0.001ML) on wafers will be tolerated by the year 2007. However, current cleanroom conditions leave surfaces vulnerable to contamination. Cleanroom oxidation prior to the pre-gate oxidation step can contaminate the surface and lead to surface roughening. In this work, it has been observed that sub-monolayer oxide develops on hydrogen terminated silicon surfaces in an hour in typical room air and lighting conditions. An hour is the average sitting time for wafers prior to gate oxidation[1],. To reduce the contamination of the hydrogen passivated silicon surfaces, the factors present in a cleanroom that affect contamination need to be identified. Some of the factors include the ambient gases and the light wavelength, such as the UV and near UV wavelengths of light emitted by the Philips TL730 lamp that is typically used by facilities at Stanford University,. The main objective of our research is to identify the primary factors that lead to cleanroom contamination and then in future work to investigate the mechanism of the specific contaminant’s nucleation and growth. EXPERIMENTAL DETAILS Prime, n-type phosphorus doped silicon (111) and (100) oriented wafers with 1 to 10Ω⋅cm resistivity are used in this research. Silicon samples are first cleaned using a piranha solution B6.8.1 Downloaded from https://www.cambridge.org/core. Access paid by the UCSB Libraries, on 03 Sep 2017 at 10:52:24, subject to the Cambridge Core terms of use, availabl
Data Loading...
