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Published May 1995 | Published
Journal Article Open

Hyperthermal neutral beam etching


A pulsed beam of hyperthermal fluorine atoms with an average translational energy of 4.8 eV has been used to demonstrate anisotropic etching of Si. For 1.4 Hz operation, a room-temperature etch rate of 300 Å/min for Si(100) has been measured at a distance of 30 cm from the source. A 14% undercutting for room-temperature etching of Novolac-masked Si features was achieved under single-collision conditions, with no detectable mask erosion. Translational energy and angular distributions of scattered fluorine atoms during steady-state etching of Si by a normal-incidence, collimated beam demonstrate that unreacted F atoms can scatter inelastically, retaining a significant fraction of their initial kinetic energies. The observed undercutting can be explained by secondary impingement of these high-energy F atoms, which are more reactive upon interaction with the sidewalls than would be expected if they desorbed from the surface at thermal energies after full accommodation. Time-of-flight distributions of volatile reaction products were also collected, and they show evidence for a dominant nonthermal reaction mechanism of the incident atoms with the surface in addition to a thermal reaction channel.

Additional Information

© 1995 American Vacuum Society (Received 5 October 1994; accepted 6 March 1995) This work was carried out at the Jet Propulsion Laboratory (JPL), California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). This research was supported by the Ballistic Missile Defense Organization/Innovative Science and Technology Office and by NASA through a grant from the JPL Director's Discretionary Fund. The authors are grateful to Dr. Charles W. Jurgensen at AT&T Bell Laboratories for supplying masked silicon wafers for this experiment. One of the authors (K.P.G.) thanks the Camille and Henry Dreyfus Foundation for a New Faculty award.

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