AES and XPS characterization of TiN layers formed and modified by ion implantation

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1 Semiconductor Physics, Quntum Electronics & ptoelectronics V. 2, N 3. P PACS: 85.4.L; T; L AES nd XPS chrcteriztion of TiN lyers formed nd modified y ion implnttion V. Melnik, V. Popov, D. Kruger*,. eremok Institute of Semiconductor Physics, NAS of Ukrine 45, prospect Nuki, Kyiv, Ukrine. Tel/Fx: (3844) * Institute of Semiconductor Physics, Wlter-Korsing-Str.2, 1523 Frnkfurt (der) Germny. Tel. (49335) Fx. (49335) Astrct. Compositionl chrcteriztion of sputtered nd implnted titnium nitride (TiN) lyers for microelectronics ppliction is performed sed on Auger Electron Spectroscopy (AES) nd X-ry induced Photoelectron Spectroscopy (XPS) dt. AES shows strong overlpping of the most intensive peks of Ti nd N. A simple empiricl method using intensity reltions of Auger spectr is developed for quick estimtion of lyer composition in smll res. Defined modifiction of the TiN lyers ws relized y mens of cron nd oxygen implnttion to study their influence on quntittive nlysis. In difference to stndrd AES nlysis the results of quntifiction using the method proposed re found to e in good greement with XPS profiles nd with results from Principl Component Anlysis (PCA), where pek overlpping is excluded. The influence of oxygen ws found to e crucil for stndrd AES nlysis ut it could e tken into ccount in the proposed method. High cron concentrtions show no significnt influence on the Ti nd N pek shpes. Keywords: ion implnttion, titnium nitride, uger electron spectroscopy, X-Ry photoelectron spectroscopy, component nlysis, microelectronics, optoelectronics. Pper received ; revised mnuscript received ; ccepted for puliction Introduction 1999, Institute of Semiconductor Physics, Ntionl Acdemy of Sciences of Ukrine Titnium nitride films re perspective in wide re of pplictions, rnging from hrd nd corrosion resistnt cotings [1] to diffusion rrier lyers for dvnced electronic devices [2-4]. Different formtion techniques such s physicl or chemicl vpor deposition, nd mgnetron sputtering hve een pplied. During the lst few yers the use of ion implnttion for the formtion of TiN ttrcts ttention [5]. The modifiction of composition, microstructure nd strin in these lyers is under investigtion to optimize their properties. Therefore, strong need for lterlly resolved quntittive chrcteriztion rises. For lrge structures in the 1 2 mm 2 rnge X-ry induced Photoelectron Spectroscopy (XPS) with its high energy resolution llows to seprte the peks of the elements in the spectr nd to perform compositionl nd chemicl quntifiction. However, for nlyzing su-micron res nd smll defects in semiconductor metlliztion structures only Auger Electron Spectroscopy (AES) seems to stisfy the resolution requirements of the SEMATECH Metrology Rodmp [6]. Two min fctors hinder the Auger qulittive nd quntittive nlysis of TiN lyers. Firstly, the Ti LMM pek overlps the N KLL pek t pproximtely 387 ev kinetic energy which is the predominnt trnsition of nitrogen. This overlp is so severe tht the peks re completely superimposed. Secondly the line shpe depends on chemicl onding in the Ti compounds, giving rise to dditionl errors in quntittive nlysis. The Trget Fctor Anlysis (TFA) [7] nd the method used t Chrles Evns Assocition [8] re sophisticted exmples for quntittive nlysis. The ppliction of these methods requires the specificlly equipment nd softwre, which is not lwys ccessile. In the given work we present AES nd XPS chrcteriztion of sputtered TiN films nd nneled TiN lyers formed nd modified y mens of high dose ion implnttion. A simple empiricl method, sed on intensity reltions of the AES peks is developed nd proposed for quick estimtion of lyer composition. Into some of these lyers cron nd oxygen (the impurity which usully re found with the nlysis) were dditionlly implnted to study their influence on quntittive nlysis. The results of AES quntifiction re compred with XPS profiles nd results from Principl Component Anlysis (PCA). 2. Experimentl detils To investigte the formtion of nneled TiN lyers we implnted N + ions t room temperture nd t 5 C into me- 81

2 V. Melnik et l.: AES nd XPS chrcteriztion of TiN lyers... chniclly polished Ti smples nd sputter deposited Ti lyers on Si sustrtes. An implnttion energy E = 1 kev nd dose in the rnge of cm -2 to cm -2 were chosen. Thin TiN films (3 nm - 1 nm) deposited on Si y mens of mgnetron sputtering in N 2 -tmosphere, nd TiN/TiSi /Si structures were lso used for comprison. AES nd XPS depth profiles were mesured to determine the lyer composition. The sic Auger nlyses were crried out using 1 kev, 1 na electron em with em dimeter of out 5 nm on the «PHI 67» instlltion. For definition of universlity of offered method some prt of mesurements were crried out on instlltion 9-ÈÎÑ-5 with difffering technicl prmeters using 3keV, 1mA electron em with em dimeter of out 1 µm. The XPS dt were otined using monochromtic AlK ( ev) X-rys. For sputter depth profiling we used 4 kev Ar + em rstered over 1.5 x 1.5 mm 2 (PHI67), 2,5 kev Ar + em rstered over 2 x 3.5 mm 2 (9-ÎÑ-5) for AES nd over 4x4 mm 2 for XPS. Lterlly resolved AES mesurements were performed to chrcterize sumicron TiN metlliztion defects. XPS quntifiction hs een performed using sensitivity fctors clirted y mens of stoichiometric TiN lyers. 3. Results nd discussion Fig.1 shows the results of AES pek shpe mesurements on reference smples of the min Auger trnsitions of Ti in Ti, Ti x, TiN y, TiSi z. The most intense peks re the LMM nd LMV trnsitions ner 387 ev nd 42 ev; intensities of tht re designted s Ti(1) nd Ti(2), respectively. With the emission of vlence electrons the LMV line is sensitive to chemicl onding, which results in splitting of the oxide nd nitride lines. Chnges in pek shpe occur lso for the LMM line. The indicted spectr cn serve s fingerprints for informtion out composition nd phse. Additionl informtion cn e extrcted from the Ti-LVV pek t 27 ev (not shown) nd the Ti-LMM pek t 451 ev which re not influenced y the N-KLL (385 ev) pek. The pek-to-pek heights (PPH) of the intense peks Ti(1) nd Ti(2), otined from smples with different composition cn e used s reltive nd pproximte mesure of the depth distriution of the elements in the lyer. Fig.1 shows depth profile through TiN x / TiSi y structure, which is oxidized in the ner-surfce region. Strting from the Si sustrte plteu region is indicted y the Si nd Ti intensities. This region is relted to the TiSi y lyer formed y solid-stte rection of Ti nd Si. The next lyer contins no Si nd is chrcterized y n pproximtely constnt pek intensity of Ti(2) ut incresing the Ti(1) one, which indicts lyer with the nitrogen content incresing towrds the surfce. The surfce lyer is oxidized s cn e concluded from the oxygen profile nd the pek shpe nlysis (not shown) nd is relted to Ti z phse. Although, the rtio of the pek intensities Ti(1) (which is strongly influenced y N-KLL) nd Ti(2) cn e used for rough chrcteriztion of different Ti compounds, simple ppliction of elementl sensitivity fctors s in stndrd quntifiction techniques yields in incorrect concentrtions of such smples. Suitle dt processing re required for more ccurte nd quntittive nlysis of TiN x lyers, especilly of those contining oxygen. To fricte smples with different compositions of TiN x, high dose N implnttion into Ti ws performed. A typicl depth profile using the pek-to-pek heights (in ritrry units) for n implnttion doses of cm -2 is shown in Fig.2. Fig.2 shows the result of TRIM 98 clcultion. As it is seen from comprison of Figs 2, 2, with incresing N concentrtion the Ti(1) intensity increses wheres the Ti(2) intensity remins lmost unchnged. We determined the rtio of the PPH intensities n = Ti(2)/Ti(1) for pure Ti nd in our experimentl conditions. The intensity reltion Ti(2)/Ti(1) vries from 1.5 for pure Ti to.5 for TiN. Anlyzing the dependence of the intensity reltion Ti(2)/Ti(1) on nitrogen concentrtion, the following ex- 8 Ti1 Derivtive pek height,.u Derivtive pek height,.u Ti2 Si Kinetic energy, ev Kinetic energy, ev Fig.1. (): Auger line shpes of the Ti-LMM pek for different Ti compounds; (): Auger depth profile of TiN/TiSi/Si structure using the pek-to-pek heights of the Si-LVV, Ti-LMM, (overlpping with N-KLL), Ti-LMV, nd -KLL trnsitions. 82 SQ, 2(3), 1999

3 V. Melnik et l.: AES nd XPS chrcteriztion of TiN lyers... Derivtive pek height,.u Ti1 Ti2 C o n ce n tr tion, t. % Fig.2. (): Auger depth profile of N implnted polished Ti smple (E = 1 kev, D = cm- 2 ) using the pek-to-pek heights of the Ti-LMM, (overlpping with N-KLL), Ti-LMV, nd -KLL trnsitions; (): N concentrtion in the implnted smple clculted y mens of Equ.(1) in comprison to TRIM 98 clcultion. pression ws found empiriclly for the concentrtion rtio of N nd Ti : C N /C Ti = {[αti(1) Ti(2)]/2Ti(2)} (1) where α = Ti(2)/Ti(1) for pure Ti nd is equl to 1.5 for «PHI 67» instlltion. Eq. (1) gives simple reltionship for the determintion of N in TiN x mtrix. Fig. 2 shows the N concentrtion clculted from the depth profile in Fig.2 using Eq.(1), dditionlly to the TRIM clcultion. A good correltion is otined for the decresing prt of the profile over wide re of concentrtion rnging from out 45 t.% down to 1 t.%. However, significnt differences occur t the incresing prt of the profile ner the surfce. These differences seem to e minly relted to lrge mounts of oxygen which influence the rtio of Ti(1) nd Ti(2). The influence of oxygen on quntittive nlysis ws studied y mens of high dose oxygen implnttion into TIN x lyers. Fig.3 shows corresponding AES depth profile. As seen, the rtio of the PPH intensities Ti(2)/Ti(1) is influenced y the oxygen content. This influence is minly relted to chnges in the Ti(1) pek shpe (Ti-LMM). Fig.3 shows the influence of oxygen implnttion on the spectr. For incresing oxygen concentrtion y fctor of out 3, from 6 t.% to out 2 t.%, no significnt chnges in the PPH of the Ti(2) pek cn e detected. Therefore, the Ti(2) pek cn roughly e used for clcultion of the oxygen content in TiN lyers. With the knowledge of the oxygen influence Eq.(1) cn e used for TiN x y chrcteriztion. Fig.4 presents the results of XPS depth profile of the lyer formed y N implnttion into Ti lyer contining out 1 to 15 t.% of oxygen in the ulk of the lyer. Solid line represents the N concentrtion clculted using Eq. (1) with the ccount of the oxygen influence. Strting from this D e riv tiv e p e k h eigh t,.u. D e r iv tive p e k h e ig h t,.u. Sputter tim e, m in. Fig.3. xygen implnttion into TiN lyer on Si (E = 7 kev, D = cm -2 ): (): PPH - Auger depth profile; (): line shpes of the Ti-LMM pek for oxygen concentrtions of 6 nd 2 t.%. The rrow indictes the R p position for the implnted oxygen. SQ, 2(3),

V. Melnik et l.: AES nd XPS chrcteriztion of TiN lyers... C o n c e n tr tio n, t.% 8 7 6 5 4 3 2 1 Nclc. N Si In ten sity,.u. 5 1 15 2 25 3 35 Fig.4. N + implnttion t 5 o C into Ti lyer on Si (E = 1 kev, D = 6.

4 V. Melnik et l.: AES nd XPS chrcteriztion of TiN lyers... C o n c e n tr tio n, t.% Nclc. N Si In ten sity,.u Fig.4. N + implnttion t 5 o C into Ti lyer on Si (E = 1 kev, D = cm -2 ): (): XPS depth profile nd clculted ( from AES) nitrogen concentrtion y mens of Eqn. (1), (): TFA nlysis using the PHI-Mtl method. profile, firstly the oxygen concentrtion ws clculted using the Ti-LMV nd -KLL peks. Susequently, the N concentrtion ws otined using Eq. (1). Now much etter correltion is otined etween the dt for N in Fig. 4 in comprison to tht chieved in Fig.2. The use of Auger spectrometers of nother tipe (9 ÈÎÑ-5) hve given the sme results within the devition no more thn 2 t.%. The ppliction of the PHI-Mtl-softwre on TIN lyers is n other possiility to tke into ccount chemicl influences on Auger spectr, which hs een demonstrted y Wtson et l. [7]. The method involves first pplying trget fctor nlysis (TFA) to seprte the Auger spectr of N in Ti nd TiN. Isoltion of the spectr of N nd Ti s TiN egins with Auger spectr recorded from TiN x smples with different composition. To compre our simple pproch with other existing methods of N quntifiction we used the TFA nlysis, too. The principl component nlysis of the Ti spectrl dt shows tht the system now cnnot e descried y two eigenvectors, third hs to e tken into ccount. From XPS results this component cn e relted to Ti z phse. These three lrgest eigenvectors were reti-ned to construct the PCA solution while the remining eigenvectors (representing spectrl noise) were discrded. The result is shown in Fig.4, good correltion to Fig.4 is found. Therefore, our proposed simple pproch cn e successfully pplied for compositionl chrcteriztion of TiN x lyers contining oxygen. An interesting technologicl result, which cn e concluded from the depth profile in Fig.4, is the evidence of oxygen out-diffusion from the region where TiN is formed towrds the surfce nd the ulk of the Ti lyer. Fig.5 shows typicl exmple of.3 µm defect nlysis y mens of AES in su-micron TiN structures. As it is seen from the superimposed line-scns, the defect is relted to Ti z inclusion into the TiN lyer. The quntifiction procedure of Eq.(1) cn esily e used to chrcterize lterl inhomogenous TiN lyer formtion in dvnced microelectronic structures. Fig.5. Filure nlysis of su-micron defects in TiN diffusion rriers: AES line scns using Ti-LMM, -KLL trnsitions. Summry A simple empiricl method sed on Auger pek intensity reltions is developed for quick estimtion of TiN, lyer composition in semiconductor structures. The results of quntifiction re found to e in good greement with XPS profiles nd results from Principl Component Anlysis (PCA). For defined compositionl modifiction of TiN the lyers were implnted using cron nd oxygen ions to study their influence on quntittive nlysis. The influence of oxygen ws found to e crucil for usul AES nlysis ut could e tken into ccount in the proposed method. High cron concentrtion shows no significnt influence on the Ti nd N pek shpes. 84 SQ, 2(3), 1999

5 V. Melnik et l.: AES nd XPS chrcteriztion of TiN lyers... References 1. Z. Yu, K. Ingw, Z. Jin, Triologicl Proporties of TiN nd TiC Films in Vcuum t High Temperture // Thin solid Films, 264(1), p.p (1995). 2. T. Hr, A. Ynnoue, H. lio, K. Inoue, G. Whiszu, Properties of Titnium Nitride Films For Brrier Metl in Aluminium hmic Contct Systems // Jpn. J. Appl. Phys., 3(7) p.p (1991). 3. P. Yin, S. Mruno,Bis Effect on the Microstructure nd Diffusion Brrier Cpility of Sputterd TiN nd Ti x N y Films // Jpn. J. Appl. Phys., 31(5A), p.p (1992). 4. M. Eizenerg, K. Littu, S. Ghnyem, M. Lio, R. Mosely, A. K. Sinh, Chemicl Vpour Deposited TiCN: New Brrier Metlliztion for Sumicron Wi nd Contct Appliction // J. Vc. Sci. Techn., A, 13(3), p.p (1995). 5. Y. Ksuke, J. otuo, S. Ngt, M. Kishimoto, Y. Fujino, S. Ymguchi, Y.Ymd, TiN Surfce Lyer Synthesis Using Ion Implnttion // Jpn. J. Appl. Phys., 34(7), p.p (1995). 6. «Metrology Rodmp: A Supplement to the Ntionl Technology Rodmp for Semiconductors», SEMATECH, Austin, TX, D. G. Wtson, W.F. Stickle, Physicl Electronics Division, Appliction Note, Chrles Evns & Assotites, Appliction Note AES -AN-4/1, 2/92 SQ, 2(3),

AMPERE CONGRESS AMPERE on Magnetic Resonance and Related Phenomena. Under the auspices of The GROUPEMENT AMPERE

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