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Unformatted text preview: N depth profiles in thin SiO 2 grown or processed in N 2 O: The role of atomic oxygen E. C. Carr, a) K. A. Ellis, and R. A. Buhrman b) School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853-2501 ~ Received 14 September 1994; accepted for publication 3 January 1995 ! Atomic oxygen, which can be liberated as an intermediate product in the decomposition of N 2 , is shown to be effective in removing N previously incorporated in SiO 2 layers grown in N 2 O. This removal results in a N distribution that is sharply peaked at the Si–SiO 2 interface for oxides grown in N 2 O by rapid thermal oxidation, but in a flat N distribution for N 2 O oxides grown in a furnace where the concentration of atomic oxygen is generally not substantial at the wafer position. This effect provides a means of tuning N profiles in a manner that may be useful for optimizing oxide quality. © 1995 American Institute of Physics. There is considerable interest in the enhancement of the electrical performance of thin gate and tunnel silicon oxides by the incorporation of N. One of the most favorable ap- proaches is complete or partial growth of the oxide in N 2 O. 1–3 Since the electrical improvements have been linked to the amount and location of N incorporated in the oxide, 4 it is important to understand the correlations between oxide growth conditions and the N location and concentration. It has been shown that oxides grown entirely in N 2 O by fur- nace and rapid thermal oxidation ~ RTO ! have distinctly dif- ferent N concentration depth profiles. 4 In general, furnace oxides have a more or less uniform distribution of N throughout the oxide, while the RTO oxides have a peak of N at the Si–SiO 2 interface. Here we demonstrate that the cause of this difference is a reaction involving atomic oxygen that removes previously incorporated N from the oxide during an RTO process in N 2 O. Due to the process conditions in a furnace, this reaction is largely absent from furnace growth using N 2 O. These results shed light on the stability of N incorporation in gate and tunnel oxides, indicate pathways for the optimization of N concentration profiles and provide new insight into the nature of the Si oxidation process in the presence of reactive nitrogen oxide compounds. The oxides used in this study were grown on ~ 100 ! n-type silicon wafers. After a standard clean and HF-last dip, oxides were grown in either pure N 2 O or O 2 ambient in either a conventional furnace or by RTO. The growth tem- perature for these oxides was 1000 °C, with final film thick- ness of 50–150 Å. High resolution chemical depth profiling of these samples was accomplished by x-ray photoelectron spectroscopy ~ XPS ! measurements in conjunction with a HF and ethanol spin-etch process....
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This note was uploaded on 12/10/2009 for the course IF PFIS1200 taught by Professor Antonio during the Spring '09 term at Universidade Federal do Rio de Janeiro.
- Spring '09