Appl. Phys. A 58, 541-549 (1994) Applied ,o,,,,, Physics A-" Surfaces © Springer-Verlag 1994 On the Influence of Extrinsic Point Defects on Irradiation-Induced Point-Defect Distributions in Silicon J. Vanhellemont, A. Romano-Rodriguez* IMEC, Kapeldreef 75, B-3001 Leuven, Belgium (Fax: +32-16/281501) Received 18 November 1993/Accepted22 February 1994 Abstract. A semi-quantitave model describing the in- fluence of interfaces and stress fields on {ll3}-defect generation in silicon during 1-MeV electron irradiation, is further developed to take into account also the role of extrinsic point defects. It is shown that the observed distribution of { 113}-defects in high-flux electron-irradi- ated silicon and its dependence on irradiation tempera- ture and dopant concentration can be understood by tak- ing into account not only the influence of the surfaces and interfaces as sinks for intrinsic point defects but also the thermal stability of the bulk sinks for intrinsic point defects. In heavily doped silicon the bulk sinks are related with pairing reactions of the dopant atoms with the generated intrinsic point defects or related with enhanced recombination of vacancies and self-interstitials at ex- trinsic point defects. The obtained theoretical results are correlated with published experimental data on boron- and phosphorus-doped silicon and are illustrated with observations obtained by irradiating cross-section trans- mission electron microscopy samples of wafers with highly doped surface layers. PACS: 61.80.Fe, 61.70.Bv, 61.70.Yq Irradiation of electronic devices with high energy parti- cles leads to a degradation of the device characteristics which is partly due to the creation of lattice damage in the active areas of the devices. A convenient way of studying the basic mechanisms of the formation of radia- tion-induced displacement damage is irradiation with MeV electrons which is known to create individual in- trinsic point defects rather than extensive collision cas- cades. Low flux electron irradiation leads to the forma- tion of point defect complexes such as divacancies and dopant/intrinsic point defect pairs. High fluxes of MeV * Permanent address: LCMM, Departament de Fisica Aplicada i Electrbnica, Universitat de Barcelona, Diagonal 647, E-08028 Bar- celona, Spain electrons create a supersaturation of self-interstitials which cluster in so-called {ll3}-defects which can be observed in situ during irradiation in a High-Voltage transmission Electron Microscope (HVEM). The distri- bution of {113}-defects in the irradiated sample can be used to monitor local variations of the intrinsic point- defect concentration. Already in 1981, Brown and Fathy [1] observed a strong dependence of { 113}-defect generation on the type and the concentration of dopant atoms. Aseev and co- workers [2-5] have studied this phenomenon in more detail using silicon samples doped with different con- centrations of boron or phosphorus atoms. Recently, experimental results were also obtained by the present authors by irradiating cross-section samples of wafers with a dopant concentration depth profile [6-9]. The impact of interfaces and localised mechanical stress fields on the {ll3}-defect distribution was discussed in a previous paper in which a first order model was presented to explain the generation of {ll3}-defects near TEM specimen surfaces and interfaces [10]. Other extrinsic point defects which are not electrically active play also an important role in the {ll3}-defect nucleation and growth. Hua et al. [11, 12] showed that interstitial oxygen enhances the { 113}-defect nucleation, which is much lower in oxygen lean FZ material. The experiments of Hasebe et al. [13] and by the present authors [7] demonstrated the important impact of carbon diffusing in from the specimen surface and leading to an enhanced initial defect formation near this surface. Ni- trogen on the contrary is reported to suppress strongly {ll3}-defect nucleation even for a nitrogen concentra- tion as low as 1015 cm -3 [14]. A similar suppression of defect formation is observed in germanium-doped silicon or in silicon/germanium alloys [8, 15]. In the present study an attempt is made to extend the first order model of [10] to explain also the observations obtained after irradiation in a high voltage transmission electron microscope of plan view and cross-section spe- cimens of highly doped silicon. It is shown that the published data on {113}-defect generation in uniformly