AVS 45th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS1-WeM

Paper SS1-WeM3
Chemistry and Intermolecular Interactions of Nitridation and Oxidation Precursors on Si(100)-(2x1)

Wednesday, November 4, 1998, 9:00 am, Room 308

Session: Physics of Semiconductors
Presenter: K.T. Queeney, Bell Laboratories, Lucent Technologies
Authors: K.T. Queeney, Bell Laboratories, Lucent Technologies
A.B. Gurevich, Columbia University
X. Zhang, Rutgers University
E. Garfunkel, Rutgers University
J. Eng, Jr., Bell Laboratories, Lucent Technologies
B.B. Stefanov, Bell Laboratories, Lucent Technologies
K. Raghavachari, Bell Laboratories, Lucent Technologies
Y.J. Chabal, Bell Laboratories, Lucent Technologies
Correspondent: Click to Email
The manner in which various molecules adsorb, dissociate and interact on silicon surfaces can dramatically affect their subsequent incorporation into the silicon substrate and thus the nature of compounds formed at higher temperatures.@footnote 1@ We have studied mechanisms leading to oxidation, nitridation and oxynitridation of silicon via investigations of the structure and reactivity of H@sub 2@O, NO, NH@sub 3@ and N@sub 2@H@sub 4@ on Si(100)-(2x1). Dissociation of these molecules on a single Si-Si dimer yields well-defined structures which are identified using high-resolution infrared absorption spectroscopy in a new, sensitive transmission geometry, together with density functional cluster calculations. This powerful combination of theory and experiment also reveals subtle frequency shifts associated with the inter-dimer interactions of surface intermediates. For example, in the case of water adsorption, hydrogen bonding between two hydroxyl groups on neighboring dimers leads to splitting of all the observed vibrations (@nu@(SiO-H), @nu@(Si-H), @delta@(Si-H), @delta@(Si-OH) and @nu@(Si-O)). The magnitude of these splittings (@>=@ 10 cm@super -1@) allows definitive characterization of these interactions with infrared spectroscopy. For instance, two @nu@(OH) peaks corresponding to coupled hydroxyls appear at 3675 and 3660 cm@super -1@, well resolved from the uncoupled O-H stretch at 3684 cm@super -1@; likewise, the two @nu@(Si-O) features of coupled hydroxyl groups are split to 14 cm@super -1@ above and 12 cm@super -1@ below @nu@(Si-O) of the uncoupled species. Similar effects are observed after co-adsorption of water and ammonia. Such interactions provide a natural mechanism for local oxygen and nitrogen agglomeration during the thermal evolution of these surfaces, observed by monitoring changes in @nu@(Si-H) as well as Si-N and Si-O vibrations as atomic nitrogen and oxygen insert into Si backbonds at higher temperatures. @FootnoteText@ @footnote 1@M. K. Weldon, B. B. Stefanov, K. Raghavachari and Y. J. Chabal, Phys. Rev. Lett. 79, 2851 (1997).