A Study of the Effects of Implantation Dose and Annealing Temperature on the Formation of Buried Nitride SOI Structures
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A STUDY OF THE EFFECTS OF IMPLANTATION DOSE AND ANNEALING TEMPERATURE ON THE FORMATION OF BURIED NITRIDE SOT STRUCTURES M.B. KERGER*, R. KWOR*, M. ZELLER*, P.L.F. HEMMENT** AND K.J. REESON** *Department of Electrical and Computer Engineering, University of Notre Dame, Notre Dame, IN 46556 "**Department of Electronic and Electrical Engineering, University of Surrey, Guildford, Surrey GU2 5XH, England ABSTRACT Nitrogen implantation into single-crystal silicon can result in a SOT structures buried nitride layer under proper processing conditions. have been formed using this technique. The optimum parameters for forming a buried nitride layer with good insulating characteristics have been investigated. Nitrogen was implanted into silicon at 200 keV at an implanta0 tipp tem erature of O 0°C. The effect of im*lantation doses of 1.05 x and post-implantation 101N+/cm , 1.3 x 10lN+/cm and 1.4 x IlN /cm 0 annealing temperatures of 1050, 1100, 1150, and 1200 C on the buried nitride layer was studied. Transmission Infrared Spectroscopy was used to determine The the structure (amorphous or crystalline) of the buried nitride layer. infrared spectra change as a function of annealing temperature, indicating the transition from amorphous to crystalline silicon nitride. Leakage currents through the structures were measured and SEM micrographs of the nitride surfaces were taken. The correlation between the IR results and these data will be presented. INTRODUCTION SOl structures have been fabricated using nitrogen ion implantation into silicon to form a buried silicon nitride layer. These structures are not fully understood. Various implantation doses, energies and temperatures have been investigated, along with various post-implantation annealing times and temperatures; but the optimum processing parameters for producing a consistently good quality SOl structure have not been determined [1,2,3,4]. Earlier work on nitrogen implantation into silicon has produced values for some of these parameters. For example, it has been found that if the nitrogen ion dose is too low, a continuous Si 3 N4 layer is not formed during implantation [3]. lilicon nitride precipitates have been found to form for a dose of 3 x 10 N+/cm 2 implanted at an energy of 150 KeV [5]. In practice, the doses of interest are those around the dose necessary to form stoichiometric Si N at the peak of the nitrogen concentration profile. It has been found thaI for implantation doses below that needed to form stoichiometric Si 3N4 , the nitrogen "pulls in" from the edges of the distribution profile during high temperature post-implantation annealing to form a Si 3N4 layer with abrupt Si/Si 3 N4 interfaces [6]. Thus, doses slightly below those needed to form stoichiometric Si 3 N4 can form a silicon nitride layer [3]. Also, it has been determined that a high implantation temperature (above 300 0 C) is necessary to keep the top silicon layer from becoming completely amorphous. If the silicon overlayer is completely amorphized during implanIf the silicon is tation, then during
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