NOM zyxwvutsrqpo B Nuclear Instruments and Methods in Physics Research B77 (1993) 184-187 North-Holland zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Beam Interactions with Materials&Atoms Channeling STIM and its applications M. Cholewa ‘, A. Saint, G.J.F. Legge and D.N. Jamieson zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQ Micro Analytical Research Centre (MARC), School of Physics, The University of Melbourne, Parkuille, fit. 3052, Australia T. Nishijima Electrotechnicat Laboratory, I-l-4, Ume.zorw, Tsukuba, Ibaraki Japan Channeling scanning transmission ion microscopy (CSTIM) has been used to explore transmission channeling in thin Si and Sic crystals. The CSTIM technique was applied to the investigation of the quality of - 30 pm thick Sic crystal. In this work the results from channeling contrast microscopy (CCM) were combined with CSTIM. The channeling STIM (CSTIM) technique is almost 100% efficient, which reduces the analysis time, and the beam causes negligible damage, compared to backscattering channeling contrast microscopy (CCM). CSTIM is capable of very high resolution (50 nm). These features can be successfully applied to the investigation of crystal damage and small size imperfections in samples transparent to the beam. 1. Introduction Silicon carbide (SE) is an excellent materiaf for high temperature semiconductor devices, because of its electronic properties, such as its wide band gap and high electron mobility. It is then expected that Sic electronic devices will be insensitive to radiation dam- age [l]. In this paper we used a combination of chan- neling contrast microscopy [2] and channeling STIM [3] techniques to investigate Sic crystal. Ion beam techniques are important in the formation and in the analysis of semiconductor devices and many new materials. For the last decade, since Inga~ield et al. [4] commenced channeling with a microbeam of alpha particles and MacCaIlum et al. [Z] developed CCM, these techniques have been utilised in the labo- ratory to study the properties of individual small crys- tals and in particular the damage caused by ion bom- bardment. Although CCM is a valuable technique, the large beam currents required (N I nA) limit the spatial resolution to a few microns and limit the amount of information that can be gathered from one location of the specimen before damage induced by the analyzing beam becomes si~fi~nt. These matters were dis- cussed by Williams et al. [5] and Jamieson et al. [6], and modifications to previous estimates were made more recently by Dooley and Jamieson [7]. With thin specimens, channeling of ion beams can also be examined in transmission [8,9] (0’ scattering). The required beam currents are then very low due to 1 Permanent address: institute of Nuclear Physics, Cracow, Poland. the high detection efficiency. We showed recently [3] that scanning transmission ion microscopy @TIM) [IO] and CCM could be combined to carry out high resolu- Eion channeling measurements with negligible accom- panying damage to the specimen. That first demonstra- tion of channeling STIM (CSTIM) utilised a 3.9 MeV proton beam of less than 0.5 fA to channel through a 58 km thick crystal of silicon and required a very low charge dose (- 200 fC) for the examination. This is much less than the 5.8 PC charge dose needed to produce observable damage when channeling in the (11.1) channel direction - an energy dose consistent with that found in other work [5-71. In this work we apply the CSTIM technique to thin crystals of silicon (- 3 Frn) and thick crystals of silicon carbide (- 30 Frn) and compare results with those obtained with CCM (which here denotes channeling RBS). Data collected with the SiC sample, both CSTIM and CCM, show extreme sensitivity of the first tech- nique to the channeling properties. 2. Expedients and results The crystal of silicon was about 3 p.m thick and aligned in the (111) channeling direction. A beam of 2.3 MeV alphas was focussed to a spot of less than 200 nm diameter with beam current less than 1 L4. Trans- mitted alpha particles were detected at 0” by a surface barrier detector with energy resolution of 15 keV full width at half maximum (FWHM). A collimator in front of the detector limited the acceptance angle to O-23 mrad. Old-583X/93/$06.~ 0 1993 - Elsevier Science Publishers B.V. All rights reserved