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Process for Minimizing Electron Trapping in Surface Effect Devices Produced by Secondary Ion Beam Deposition

IP.com Disclosure Number: IPCOM000048960D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Bojarczuk, NA: AUTHOR

Abstract

This article describes a method for reducing electron traps formed in metal oxide semiconductor (MOS) structures during fabrication. The method features use of a neutralized ion beam of prescribed gas maintained over a prescribed range of beam currents and beam voltages to sputter-deposit the structure's metal layer.

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Process for Minimizing Electron Trapping in Surface Effect Devices Produced by Secondary Ion Beam Deposition

This article describes a method for reducing electron traps formed in metal oxide semiconductor (MOS) structures during fabrication. The method features use of a neutralized ion beam of prescribed gas maintained over a prescribed range of beam currents and beam voltages to sputter-deposit the structure's metal layer.

Metal oxide structures fabricated using this method show improved performance. The improvement in performance has been attributed to reduced numbers of electron traps formed at the metal oxide interface. Trapping sites formed at the metal oxide interface of, for example, a MOS device, degrades performance. The trapping levels result in reduced device life and increased device instability. Where the device metal layer is deposited using conventional diode sputtering, it is believed that trapping sites arise as a result of damage induced in the oxide layer. This damage may be caused by photons generated during ionization of the sputtering gas, X-rays generated when the sputtering gas liberates target metal for deposition, and energy transfer when the depositing metal strikes the insulating layer's surface.

To reduce such damage, this method features use of an ion beam produced by ionizing a gas having a first ionization energy approximating the band gap of the device insulation layer. The gas for the ion beam is selected on this basis because it is believed that photons generated during beam ionization will not be so energetic, relative to the insulation layer band gap, as to create trapping sites within it. Additionally, the method requires that the ion beam be neutralized before it interacts with the deposition metal target to limit the presence of photons in the region of the substrate, which may cause damage.

The method also requires that the ion beam voltage...