Electrical Properties of Nitrogen and Oxygen Ion Implanted Silicon

Abstract

<p>The electrical properties of nitrogen and oxygen ion implanted silicon samples have been investigated as a function of various implantation and annealing conditions.</p> <p>The temperature dependence of the electrical characteristics of the implanted samples were analysed and the results were compared with the ones obtained from experiments performed on typical bulk silicon samples. A unique computer controlled automatic system (J . Shewchun et al.) was used for the low temperature conductivity and Hall effect measurements. Donor behaviour of the implanted layers was observed in both the nitrogen and oxygen implantation cases. It has been established that very low conversion efficiency can be achieved in the nitrogen and oxygen implants. Less than 1% of the implanted ions became active after a high temperature (325°C) anneal. The activation energies of donor like impurities were determined by analysing the carrier concentration versus reciprocal temperature graphs. It has been concluded that the form of the above graphs can only be described by a partially compensated semiconductor model which has more than one donor energy level. A model containing two monovalent kinds of donors with different energy levels and some assorted compensating acceptors was used to fit the carrier concentration vs. (1/T) curves. The activation energies of donor impurities were determined to be ED1= 0.016 ± 0.001 (eV), ED2 = 0.034 ± 0.003 (eV) for the nitrogen implants and ED1 = 0.021 ± 0.001 (eV) 1 + E = 0.031 - 0.001 (eV) for the oxygen implanted silicon. We found the above ionization energies consistent and independent of the implantation and annealing conditions.</p> <p>This study showed that the active impurity centers in the implanted layers could be well controlled by the implanted total dose, and were reproducible in the concentration range which is generally used in device fabrications.</p>