AVS 47th International Symposium
    Semiconductors Wednesday Sessions
       Session SC+EL+SS-WeM

Paper SC+EL+SS-WeM8
Variable Temperature Study of Hydrogen and Deuterium Passivation of the Si(100)-2x1 Surface using the Scanning Tunneling Microscope

Wednesday, October 4, 2000, 10:40 am, Room 306

Session: Passivation and Etching of Semiconductors
Presenter: N.P. Guisinger, University of Illinois
Authors: M.C. Hersam, University of Illinois
N.P. Guisinger, University of Illinois
K. Cheng, University of Illinois
J. Lee, University of Illinois
J.W. Lyding, University of Illinois
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Deuteration of dangling bonds at the Si/SiO@sub 2@ interface has led to a significant reduction of hot carrier degradation in complementary metal-oxide-semiconductor (CMOS) circuits. Although CMOS transistors are annealed in a D@sub 2@ environment, the presence of H in the oxide leads to the interface being unavoidably exposed to both H and D during the passivation process. Thus, an understanding of the parameters that affect the equilibrium quantities of H and D on Si surfaces is of notable interest. In this paper, the relative concentrations of H and D on the Si(100)-2x1 surface are studied following in situ passivation under conditions of equal H and D pressure. Electron stimulated desorption with a scanning tunneling microscope allows for atomically precise determination of the H and D levels. The ratio of D to H on the Si(100) surface is measured to be ~50 and ~5 following monolayer passivation at 350 K and 650 K respectively. This behavior can be qualitatively understood through a statistical thermodynamics model. Ultimately, the magnitude of the D:H ratio and its inverse relationship with passivation temperature result from the difference in the vibrational frequencies for Si-H and Si-D bonds. These results imply that the optimal deuteration of silicon dangling bonds in the presence of background H should occur at low sample temperatures. Since CMOS processes are continually reducing their thermal budgets to accommodate additional metal layers and novel materials (e.g., low k dielectrics), this paper fundamentally suggests that deuteration of the Si/SiO@sub 2@ interface could improve as processing temperatures are inevitably lowered in the future.