Pergamon Vacuum/volume 45/number 4/pages 413 to 417/l 994 Copyright @ 1994 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0042-207X/94$6.00+.00 Al-Ti reactive interdiffusion studied by STIMS and RBS P Maugis, Laboratoire de Physique des Solides, Universitb Paris-Xl, 91405 Orsay Cedex, France and YSerruys. DTAICEREMIDTMISRMP, Centred’EtudesdeSaclay,91191 Gif-sur-YvetteCedex, France The study of the kinetics of formation of the L P-L T phase during annealing of aluminium thin films on titanium is a good example of the performance of secondary thermo-ionization mass spectroscopy (STIMS) and Rutherford backscattering spectrometry (RBS). Concentration profiles obtained with both methods are in remarkable agreement as concerns the composition of the phases and the existence of a very little concentration step corresponding to the interface between TiAI, and the LP-L T phase. The results show the advantages of STIMS, as compared to SIMS, for quantitative analysis and the accuracy of the new RBS profile reconstitution method. They also show the utility of RBS for estimating the influence of sputtering effects on the broadening of concentration profiles obtained by STIMS. 1. Introduction One can wonder whether the kinetics of reactive interdiffusion between Ti and Al will really allow the formation of the com- pounds predicted by the equilibrium phase diagram and what their stoichiometry will be. Particularly, we have been interested in the conditions of apparition of the so-called LP-LT phase T&AI,,, during anneal- ing of thin Al films on Ti substrates at temperatures between 300 and 800 ‘XI. Chemical composition vs depth has been determined using both secondary thermo-ionization mass spectrometry (STIMS) and Rutherford backscattering spcctrometry (RBS). This study exemplifies the complementary advantages of both techniques and their ability to distinguish between phases of approaching composition. There is a number of intcrmctallic ordered compounds in the low temperature part of the AI-Ti phase diagram (Figure I). Reactive interdiffusion from thin layers allows the study of the thermodynamics and kinietics of incipient growth of these com- pounds. For the purpose of exemplifying the advantages of associated STIMS and RHS, we focus on the LP-LT phase. which is an ordered Ti,AI?, compound with a long period structure. 2. Experimental 2.1. Sample preparation. The titanium substrates are mono- crystalline. They are zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA firslt mechanically polished, then sputter- cleaned by argon bombardment just before vapour deposition. The aluminium layers arc vapour-deposited at a rate of I nmjs in a vacuum better than 2 x IO-’ torr. The total amount of deposited aluminium is typically 100 nm, as measured using a quartz balance. 2.2. Thermal treatment. Thermal treatments are performed in the same vessel and under the same vacuum conditions, by heating the substrate on its back side. Annealing tcmpcraturcs range from 300 to 800 C, and for durations of IO min to a few hours. 2.3. Observation and analysis. Concentration profiles arc dctcr- mined by both SUMS and RBS. STIMS results are completed for oxygen profiles using classical SIMS. Additionally, metallographic observations have been per- formed using SEM. 2.4. Secondary thermo-ionization mass spectrometry 2.4.1. Experimental. STIMS has proved to be an efficient tech- nique for profile determination in similar studies, e.g. thin film zyxwvutsrq 1600 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJI 0 10 20 30 40 50 60 70 80 90 100 c,, (at %) zyxwvutsrqponmlkjihgfedcb Figure 1. Al&Ti phase diagram. 413