Showing papers by "Robert E. Walkup published in 1990"
Patent•
IBM1
TL;DR: In this article, a narrow band-pass interferometric filter with respect to incident light was used to detect trace constituents in a plasma during processing semiconductor devices such as transistors.
Abstract: An interferometer (18 or 40) is used to identify trace constituents in a plasma during processing semiconductor devices such as transistors. Light emissions collected from the processing chamber (10) are collimated by lens (14) and transmitted to the interferometer (18 or 40) which selectively allows therethrough particular wavelengths of light which are characteristic of the excitation emissions of certain atoms such as sodium and copper. The light intensity at the selected wavelengths is sensed by a photomultiplier tube (30). In one embodiment, the interferometer (18) is a Fabry-Perot type interferometer and the separation of the plates (20 and 22) which form the Fabry-Perot etalon is controlled using a piezoelectric driver (26). A signal processor (34) correlates the sensed light emissions from the photomultiplier tube (30) with the selected wavelength that is determined by the piezoelectric driver (26). In another embodiment, the interferometer (40) is a narrow bandpass interferometric filter which is tiltable with respect to the collimated incident light from the processing chamber (10). Tilting a narrow bandpass interferometric filter (42) with respect to incident light changes the path length through the filter (42) and allows for the selective transmission of certain wavelengths of light. By rapidly tilting the narrow bandpass interferometric filter (42) at a rate between 5-300 Hz with respect to the incident light, a narrow range of wavelengths on the order of 3 nm can be scanned.
32 citations
IBM1
TL;DR: In this paper, a local density functional approach was used to predict yields and energy distributions for Ar atoms which desorb upon ionization of physisorbed Ar. The calculated potentials provide a substantially improved description of the desorption process compared to previous models based on a classical image potential for the ion surface interaction.
Abstract: Diabatic potential energy curves are reported for ions interacting with metal surfaces. The calculations are based on a local density functional approach, which fully accounts for screening by the electrons within the metal valence band. Results for Ar+ are used to predict yields and energy distributions for Ar atoms which desorb upon ionization of physisorbed Ar. The calculated potentials provide a substantially improved description of the desorption process compared to previous models based on a classical image potential for the ion-surface interaction. Classical and quantal treatments of desorption are compared, and quantum effects in the dynamics of desorption are discussed.