114-baumvol-apl-1997-2007 - Isotopic tracing during rapid...

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Isotopic tracing during rapid thermal growth of silicon oxynitride films on Si in O 2 ,NH 3 , and N 2 O I. J. R. Baumvol a) Instituto de Fisica UFRGS, 91540-000 Porto Alegre, RS, Brazil F. C. Stedile Instituto de Quimica UFRGS, 91540-000 Porto Alegre, RS, Brazil J.-J. Ganem, I. Trimaille, and S. Rigo Groupe de Physique des Solides, URA 17 CNRS, Universite ´s Paris 6 et Paris 7, Paris 75251, France ~ Received 25 November 1996; accepted for publication 11 February 1997 ! We performed isotopic tracing of O, N, and H during rapid thermal growth of silicon oxynitride films on silicon in two different sequential, synergistic gas environments: O 2 , followed by NH 3 , then followed by N 2 O; and N 2 O, followed by NH 3 . Using nuclear reaction analysis and high resolution depth profiling, we demonstrate that the oxynitride films grow by means of thermally activated atomic transport involving the three traced species. Concomitantly, isotopic exchange processes take place. Growth in these sequential gas environments leads to oxynitride films with N concentration profiles and H concentrations different from those obtained by commonly used processes like thermal growth in N 2 O only or thermal nitridation of SiO 2 films in NH 3 1997 American Institute of Physics. @ S0003-6951 ~ 97 ! 03415-3 # Ultrathin films of silicon oxynitride on Si for gate dielec- trics can be obtained by among other possibilities, direct thermal growth in N 2 O or by thermal nitridation of SiO 2 films in NH 3 . Thermal oxides nitrided in NH 3 show superior boron-stopping properties as compared to pure oxides, due to their incorporated N. However, these dielectric films suffer from H related electron trapping, either due to H atoms pas- sivating the dangling bonds at the SiO 2 /Si interface or due to Si–N–H bonds near this interface. On the other hand, oxyni- tride films grown in N 2 O have shown superior electrical properties and reliability, 1–6 although presenting poorer boron-stopping properties due to the lower level of N incor- poration. Furthermore, hydrogen exhibits a strong isotope effect in defect generation, as shown by recent studies in which transistors lifetime improvements ~ due to reduced in- terface states generation and hot-electron degradation ! by factors of 10–50 were attained when hydrogen (H 2 ) was replaced by deuterium (D 2 ) in the final wafer sintering process. 5 These recent findings may help to understand fur- ther improvements in device performance that can be achieved when gate dielectrics are prepared by synergistic combinations of the above mentioned growth procedures. 7–11 We report here to the best of our knowledge, on the first studies of isotopic tracing of N, O, and H during thermal growth of oxynitride films in a RTP furnace in the synergis- tic gas sequences reported in Refs. 7–11, namely ~ i ! growth of a SiO 2 film in O 2 , followed by nitridation in NH 3 , and then followed by reoxynitridation in N 2 O ~ O 2 NH 3 N 2 O, samples 1–5 in Table I ! , 7–9 and ~ ii ! growth of oxynitride films in N 2 O, followed by renitridation in NH 3 ~ N 2 O
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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.

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114-baumvol-apl-1997-2007 - Isotopic tracing during rapid...

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