Large Area Continuous Electron Beam for Semiconductor Processing
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LARGE AREA CONTINUOUS ELECTRON BEAM FOR SEMICONDUCTOR PROCESSING
CAMERON A. MOORE , J. J. ROCCA , G. J. COLLINS , P. E. RUSSELL , AND J. GELLER**, *Colorado State University, Department of Electrical Engineering, Fort Collins, CO 80523; **JOEL USA, 11 Dearborn Road, Peabody, MA 01960.
ABSTRACT 2
We have achieved wide area (38 cm ) electron beam heating of semiconductor materials using a glow discharge electron beam with electron energies between 3 and 7 keV. A continuous beam 7 cm in diameter with a power density up to 2 90 W/cm was used to anneal both boron-implanted (30 keV, 2 5 x 1015 atoms/cm ) n-type silicon wafers as well as two types of Ti-Si composite films to form this titanium disilicide Annealing of the implanted samples was obtained without redistribution of the original dopant profile using a 15-sec. electron beam exposure. Formation of TiSi 2 was found to decrease the sheet resistivity of these samples a factor of.ten for both 400 A films of Ti on Si and codeposited Ti-Si mixtures of overall stoichiometry TiSi 2 . Due to the high electron beam power density achieved over a large area, one can uniformly anneal an entire wafer in a single exposure without sample or beam scanning.
INTRODUCTION Transient heating of semiconductor materials has been accomplished using a variety of sources including pulsed and continuous lasers, arc lamps, and graphite strip heaters [1]. Annealing via electron beams has also been achieved using point, [2] line, [3] and broad area sources [4]. This previous electron beam annealing work [2,3] employed high voltage (>20 kV) beams beams of small area that were focused to reach the required energy density. The broad area source used previously [4] was a high voltage (20-100 kV) high current (10-50 kA) field emission discharge that provides a 100-ns pulsed electron beam. In annealing of ion implant damage it caused liquid phase regrowth of the damaged layer thereby causing undesired redistribution of the as-implanted dopant profile [4]. More recently, an electron beam generated by a glow discharge was used to anneal ion implanted silicon [5]. In this experiment a 10-cm-diam. aluminum cathode operating in pure helium produced a maximum discharge current of 80 mA at 9 kV (unfocused electron 2 beam power density was %9 W/cm ). To achieve the necessary power density for annealing silicon the electron beam was focused to a 2-cm diameter using a magnetic lens. Silicides are generally fabricated by one of two methods: i) codeposition (via sputtering, evaporation, or chemical vapor deposition) of the constituent materials, or ii) deposition of the metallic film onto silicon; both these techniques require a subsequent heat treatment to either anneal the composite film (i) or to interdiffuse the silicon metal species and form the silicide (ii). The heat source used in the latter process typically is a furnace, but comparable results have been obtained using scanned 50-100 1m diameter continuous laser and electron beams [6] as well as exposure to arc discharges in argon of duration %100
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