Some Recent Results of Fundamental Studies on Beam-Induced Surface Processes
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SOME RECENT RESULTS OF FUNDAMENTAL STUDIES ON BEAM-INDUCED SURFACE PROCESSES JAN DIELEMAN Philips Research Laboratories 5600 JA Eindhoven, The Netherlands
Recent results of studies on the mechanism of processes induced by the interaction of beams of (reactive) particles with surfaces in UHV, often combined with concurrent bombardment of the surface with low-energy ion or excimer laser beams, are reviewed. Angular-resolved mass spectrometry combined with time-of-flight studies on the desorbing products is used as a key diagnostic. A more complete picture is obtained using several other diagnostic tools to characterize the surface before, during or after the interaction. Interactions at Si and Cu surfaces will be emphasized. The review will deal successively with data for interaction with a single beam of Cl 2 , low-energy noble gas ions or excimer laser pulses, followed by data on the concurrent interaction of crossed beams of Cl2 and low-energy noble gas ions or excimer laser pulses with these surfaces. Some conclusions will be drawn.
1. INTRODUCTION
Growth and etching of thin films, usually via the gas phase, plays a dominating role in the technology of present-day integrated circuits. The ever increasing complexity of these devices has necessitated the development of techniques providing improved quality at reduced substrate temperatures. The reduced substrate temperatures are a necessity because the delicate structures already present in the substrate should not be damaged and the improved quality is essential to get a high yield of well-performing devices. Typically these techniques use dissociation and excitation of gas molecules by plasmas or by photons to enhance surface adsorption and reaction and/or apply surface-localized energy deposition by bombardment of the adsorbate layer and nearby surface region by lowenergy electrons, ions, excited neutrals or photons to stimulate surface
Mat. Res. Soc. Syrup. Proc. Vol.128. @1989Materials Research Society
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reactions and desorption of products. A qualitative and certainly a quantitative understanding of the crucial steps in these important reaction chains is largely lacking. This hampers assessment of basic possibilities and limitations of most of these techniques. It is the object of this paper to review some recent results of studies on the mechanisms of surface reactions stimulated by low-energy noble gas ion bombardment or by nanosecond excimer laser pulses. These studies have been performed in UHV chambers in which surfaces can be exposed to one beam of particles like chemically active molecules, lowenergy noble gas ions or excimer laser photons or concurrently to two
beams, one consisting of chemically active molecules and the other of low-energy noble gas ions or excimer laser photons. The discussion will be restricted to the comprehensive studies on the interaction of lowenergy noble gas ion beams or excimer laser beams with Si or Cu surfaces in most cases in the presence of chlorine adsorbed on the surfaces from a beam of Cl2 molecules. For studi
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