Ž . Applied Surface Science 149 1999 175–180 Depth profiling of defects in nitrogen implanted silicon using a slow positron beam J.W. Taylor a, ) , A.S. Saleh a , P.C. Rice-Evans a , A.P. Knights b , C. Jeynes b a Physics Department, Royal Holloway, UniÕersity of London, Egham, Surrey, TW20 0EX, UK b School of Electronic Engineering, Information Technology and Mathematics, UniÕersity of Surrey, Guildford, Surrey, GU2 5XH, UK Abstract Ž . Positron annihilation spectroscopy PAS has been used to determine the subsurface vacancy profile in Si after implantation with 50 keV nitrogen ions for a range of fluences from 5 =10 11 to 1 =10 14 cm y2 . The spatial extent of the defect distributions was estimated by employing composite-Gaussian defect profiles in the ROYPROF positron diffusion Ž . analysis program. The results are compared with both VEPFIT and TRIM TRansport of Ions in Matter calculations. q 1999 Elsevier Science B.V. All rights reserved. Keywords: Slow positron beam; Positron annihilation; Composite-Gaussian defect 1. Introduction The detection and characterization of defects in- duced by implanting ions into silicon is of consider- able importance to the electronics industry with its incessant drive towards device miniaturization. Vari- ous techniques have been employed to investigate the damage created during implantation but it is only variable-energy positron annihilation spectroscopy Ž . PAS that permits the vacancy distribution to be obtained directly and non-destructively with a sensi- w x tivity of the order of parts per million 1,2 . Previous studies exemplifying this method include cases of implantation of argon, boron, cobalt, fluorine, he- lium, nitrogen, phosphorus and silicon ions into sili- w x con 3–9 . ) Corresponding author. Tel.: q44-1784-443457; Fax: q44- 1784-472794; E-mail: j.w.taylor@rhbnc.ac.uk The aim of this paper is to introduce the first results obtained from solving the positron diffusion model using the ROYPROF program for positron annihilation spectra of nitrogen implanted silicon samples, whilst employing a defect profile accurately approximating in shape to that of the primary va- cancy profile obtained from the Monte Carlo simula- Ž . tion program TRIM TRansport of Ions in Matter w x 10 . These results are compared and contrasted with the established method of approximating to the TRIM Ž . defect profile by using one or more box-like shapes of homogenous defect density. 2. Experimental method 2.1. Sample material and ion implantation Ž . Wafers of p-type boron doped silicon with a resistivity of ; 20 V cm were implanted using the 0169-4332r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0169-4332 99 00196-8