Abstract
Visible and ultraviolet light was employed in a series of refining experiments to reveal the kinetics of photon-enhanced oxidation of silicon. The experimental evidence then gave rise to an electron-active silicon oxidation process involving electron emission from Si into SiO2 moderating the dissociation of molecular oxygen near the interface. Photonicallystimulated oxidation enhancement then straightforwardly derives from an enhanced level of electron emission. This simple model helps to clarify normal dry thermal oxidation growth kinetics, as well as thin oxide rapid growth behavior and the charged-versus-neutral oxidant controversy. Finally, attention is called to the not generally recognized but likely role that secondary electron emission from surfaces may play in moderating the chemistry of various electron, ion and photon beam-induced surface reactions.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
E.M. Young: Photon Stimulated Oxidation of Silicon, Ph. D. Thesis, Stanford University, Department of Electrical Engineering, 1985 (Available from University Microfilms International, Ann Arbor, Michigan)
E.M. Young, W.A. Tiller: Appl. Phys. Lett.42, 63 (1983)
E.M. Young, W.A. Tiller: Appl. Phys. Lett.50, 46 (1987)
E.M. Young, W.A. Tiller: Appl. Phys. Lett.50, 80 (1987)
E.M. Young, W.A. Tiller: J. Appl. Phys.62, 2086 (1987)
I.W. Boyd: Private communication, Materials Research Society Meeting; Boston, MA, December 1987
I.W. Boyd:Laser Processing of Thin Films and Microstructures: Oxidation, Deposition, and Etching of Insulators (Springer, Berlin) 1987; particularly Chapter 4 therein, Laser Assisted Oxidation and Nitridation
R. Oren, S.K. Ghandhi: J. Appl. Phys.42, 752 (1971)
While thin-film interference, due to the growing oxide layer, does indeed modulate the effective reflectivity, the level of that modulation is beneath practical experimental resolution. See [1] for a discussion of the quantitative details
In addition to [9], the effective reflectivity actually varies in the wrong direction to account for the observed enhancement variation with wavelength. See [1] for details
While in general there always exists a component of the total enhancement which is due to local heating at the beam spot, that component is proportional to the beam power density level and is below practical significance at the low power density levels purposely utilized in these careful experiments. For example, 56.6 W/cm2 was calculated to induce only a 6.6 K temperature rise on the silicon. See [1] for details and an extended quantitative treatment of the beam heating issue
Note that, as a ratio, the % E parameter is not affected by the accelerated oxidation induced by heavy doping. The %E reflects only theadditional oxidation rate enhancement due to light stimulation
For the photogenerated excess carrier quantitative details see [1] and particularly Appendix III therein, Light-Stimulated Excess Carrier Generation
L.M. Chanin, A.V. Phelps, M.A. Biondi: Phys. Rev.128, 219 (1962).
See [1] for a detailed discussion, particularly Appendix V therein, The Dynamics of Electron Attachment to Oxygen
See [1] and particularly Appendix VIII therein, Electron Emission from Si into SiO2
Proposed and named by W. A. Tiller. For a more thorough discussion of the blocking layer idea, see W.A. Tiller: J. Electrochem. Soc.127, 619 (1980); J. Electrochem. Soc.127, 625 (1980); J. Electrochem. Soc.128, 689 (1981); J. Electrochem. Soc.130, 501 (1983). For a more thorough discussion of the compressive stress associated with this interface region, see E.A. Irene, E. Tierney, J. Angilello: J. Electrochem. Soc.129, 2594 (1982)
See [1] for details; it is interesting how closely the ratio of light generated excess electron concentration intrinsic electron concentration, as a calculated percentage, follows the numerical %E over the 900°C–750°C range that was investigated. On another matter, and in addition to what has already been mentioned in [11], note that the thermal conductivity of Si increases with decreasing temperature, excluding a beam heating explanation for this effect
See [1], Chap. 2, Synopsis of Thermal Oxidation and Related Photonic Investigations, for a very abbreviated discussion of the controversy. See the comprehensive treatment in D. N. Modlin: Effects of Electric Fields and Oxygen Ion Beams on Silicon Oxidation Kinetics, Ph. D. Thesis, Stanford University, Department of Electrical Engineering, 1983. (Available from University Microfilms International, Ann Arbor, Michigan)
For a detailed study of thin-oxide kinetics, see H. Z. Massoud: Thermal Oxidation of Silicon in Dry Oxygen-Growth Kinetics and Charge Characterization in the Thin Regime, Stanford University, Electrical Engineering Department, Ph.D. Thesis, 1983 (available from University Microfilms International, Ann Arbor, Michigan); see also H.Z. Massoud, J.D. Plummer: J. Appl. Phys.62, 3416 (1987); E.A. Irene, H.Z. Massoud, E. Tierney: J. Electrochem. Soc.133, 1253 (1986); H.Z. Massoud, J.D. Plummer, E.A. Irene: J. Electrochem. Soc.132, 2685 (1985); J. Electrochem. Soc.132, 2693 (1985); H.Z. Massoud, J.D. Plummer, E.A. Irene: J. Electrochem. Soc.132, 1745 (1985)
See [1] for the detailed discussion of these points, especially Chap. 5 therein, Electron-Active Oxidation
See [1] for details, particularly Chap. 6 therein, Photon Stimulated Oxidation Rate Constants, describing a great deal of peculiar orientation-sensitive behavior, some of which is summarized in [5]
See [1], Sect. 4.4.5, High Power Pulses, for a more complete account of the effect and the intense electron-hole plasma conditions thought to be producing it
H.Z. Massoud: J. Appl. Phys.63, 2000 (1988)
Theφ parameter was to account for an electron emissionretarding potential near the interface as a result of an accumulating electron population in the immediate oxide layer. Thus, while the dipole potential could be operationally regarded as an additive contribution to that term, the physical mechanism behind it is quite different
For a good overview of ion beam-surface interactions, see J. Melngailis: J. Vac. Sci. Technol.B5, 469 (1987). For an overview of electron beam-surface interactions, see the introductory chapter in most any volume on Scanning Electron Microscopy
For an overview of laser beam processing, see D. Bäuerle:Chemical Processing with Lasers (Springer, Berlin) 1986; see also [7]
Critical energy cross-sections for beam-molecule dissociation reactions strongly favor low energy (≪ 100 eV) interactions as opposed to typical incident ion or electron beam energies (15–50 KeV)
G.M. Shedd, H. Lezec, A.D. Dubner, J. Melngailis: Appl. Phys. Lett.49, 1584 (1986)
J.S. Ro, A.D. Dubner, C.V. Thompson, J. Melngailis: Microstructure of Gold Films Grown by Ion Induced Deposition, In:Laser and Particle-Beam Chemical Processing for Microelectronics, Materials Research Society Symposium Proceedings101, 255; D.J. Ehrlich, G.S. Higashi, M.M. Oprysko, Eds. (1988)
R.R. Kunz, T.E. Allen, T.M. Mayer: J. Vac. Sci. Technol. B, Microelectron. Process. Phenom.5, 1427 (1987)
R.R. Kunz, T.M. Mayer: Appl. Phys. Lett.50, 962 (1987)
R.R. Kunz, T.M. Mayer: Surface Chemical Reactions Stimulated by Low Energy Electron Bombardment. In:Photon,Beam, and Plasma Stimulated Chemical Processes at Surfaces, Materials Research Society Symposium Proceedings,75, 609; V.M. Donnelly, I.P. Herman, M. Hirose, Eds. (1987)
R.R. Kunz, T.M. Mayer: J. Vac. Sci. Technol.B 5, 427 (1987)
L. Sanche, L. Parenteau: Phys. Rev. Lett.59, 136 (1987)
C.F. Mason, R.G. Behrens: J. Less Common. Metals85, 21 (1982)