Dopant Dependent Extended Defect Nucleation and Growth Kinetics in Silicon During 1 MeV Electron Irradiation
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DOPANT DEPENDENT EXTENDED DEFECT NUCLEATION AND GROWTH KINETICS IN SILICON DURING 1 MEV ELECTRON IRRADIATION ALBERT ROMANO-RODRIGUEZ' AND JAN VANHELLEMONT 2 ILCMM, Departament de Ffsica Aplicada i Electr6nica, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona, Spain 2 Interuniversity Micro-Electronics Centre (IMEC), Kapeldreef 75, B-3001 Leuven, Belgium
ABSTRACT
In this paper results of a study of electron irradiation induced extended defect generation in doped silicon is presented. The irradiations are performed in-situ with 1 MeV electrons in a high voltage transmission electron microscope. Preferential generation of extended defects is observed in certain areas of the sample which can be correlated with well defined dopant concentration levels. The defect growth kinetics is studied as a function of the irradiation temperature and dose and the type and concentration of dopant. After the first irradiation experiment some of the samples received a second electron irradiation, during which shrinkage and even complete annihilation of the previously generated defects can be observed. The observed results are interpreted on the base of point defect reactions. INTRODUCTION Accelerated electrons with energies above 140 keV are known to introduce lattice damage in silicon at room temperature. For the creation of extended lattice defects, however, which can be imaged using transmission electron microscopy, quite large electron fluxes and higher electron energies and/or temperatures are required. These experimental conditions can easily be obtained by in-situ electron irradiation in a high voltage transmission electron microscope (HVEM). Numerous reports exist in the literature dealing with extended defect formation in uniformly doped silicon by high dose, high energy electron irradiation [e.g. 1-3]. Little work has however been devoted to non uniformly doped samples [4-7]. In the present paper, results are presented of an in-situ study of dopant dependent extended defect generation in silicon, using 1 MeV electron irradiation in a HVEM. The irradiation induced defect (liD) nucleation and growth is studied as a function of the irradiation conditions and of the dopant type and concentration profile. EXPERIMENTAL For this study conventional Czochralski (001) substrates with background doping concentration of about l0ol cm 2 and an interstitial oxygen concentration about 510'7 cm-3 are used as starting material. Low doses of B or P ions are implanted at room temperature. In some cases the implantation is performed through masking stripes of polysilicon or silicon oxide oriented along directions, to study the defect nucleation in two-dimensional dopant profiles. Next the wafers are furnace annealed to restore the lattice damage and to activate the dopant. To study the in-situ generation of defects cross-sectional TEM specimens are prepared from the wafers following a procedure described extensively elsewhere [8]. The 1 MeV electron irradiations are performed in the JEOL 1250 high voltage transmission electron microsco
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