On the Trapping and Thermal Release of Low Energy Noble Gases Implanted into Silicon
- PDF / 425,493 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 43 Downloads / 182 Views
ON THE TRAPPING AND THERMAL RELEASE OF LOW ENERGY NOBLE GASES IMPLANTED INTO SILICON A. VAN VEEN , P.C. DE JONG. , K.R. BIJKERK , H.A. FILIUS and J.H. EVANS " IRI, Delft University of Technology, Mekelweg 15, NL-2629JB, Delft, The Netherlands ** Materials Development Division, Harwell Laboratory, Oxon, OXi1 ORA, U.K. ABSTRACT Gas desorption spectrometry has been used to study the behavior of implanted noble gas ions in silicon. Results of low dose Ar implants followed by thermal desorption has shown the release of argon in Si from distinct surface related trapping sites, from substitutional argon (ArV) and from larger Ar-V clusters. This information gives an insight into the response of the silicon lattice to the Ar implants. For higher Ar doses, the effects of amorphization are clear in the desorption spectra and lead t6 a method of measuring the recrystallization velocity during epitaxial regrowth (v=2xl0 exp(-2.8 eV/kT). A similar value was found for thin sputtered Si films. The paper discusses high dose Ar saturation phenomena and describes the use of helium implants to probe defects and defect structures, such as bubbles and voids, in silicon. INTRODUCTION Like most materials, e.g. metals, silicon has a very low solubility for noble gases and therefore noble gas atoms become incorporated in silicon when they are surface injected with kinetic energies of a few eV and higher. There are a number of processes in silicon technology in which surfaces are exposed to fast noble gas-ions (mostly argon) : ion-milling, sputter-cleaning, chemically assisted ion beam etching and thin film deposition by sputtering. The relevant energies of the argon projectiles lie between 10 eV and 5 keV. Research on the behavior of noble gases in silicon has mainly been focussed on cases of high implantation doses so that no data are known for the elementary noble gas defects in silicon. Davies and Carter [1] have been the first who reported on gas desorption of keV implanted noble gas atoms. The role of incorporated noble gas on the sputtering process has been studied by Wittmaack [2] and Matzke [3], while later Wittmer et al [4] have reported the occurence of gas bubbles formed by 30-200 keV implanted gas atoms. Bangert et al [5] also found gas bubbles in keV irradiated silicon kept at elevated temperatures. Recently Lang and Taoufik [6] reported on Ar release observed during recrystallization of the top layers of silicon which had been rendered amorphous by high dose keV Ar-ion-bombardment. In this article results are presented of desorption1otudies oy 9 nobll gas implanted into silicon for a wide dose range from 1xl0 to lxlO cm and for energies ranging from 10 to 3000 eV. The topics that are discussed are 1. assignment of desorption peaks to noble gas defect-complexes, 2. noble gas clustering, 3. amorphization and recrystallization, 4. saturation phenomena, and 5. gas incorporation in sputtered films. EXPERIMENTAL Two helium desorption spectrometers HDS-I and HDS-II were used for the work presented here. In HDS-I low1lose expe%'ment2
