43(4)-02.fm

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1 Korean Chem. Eng. Res., Vol. 43, No. 4, August, 2005, pp 텅스텐기판위에구리무전해도금에대한연구 i Ç s * Ç mçoq Ç Ç Ç r r rte v v * s o k 1334 ( o 27p r, o 15p }ˆ) A Study of Copper Electroless Deposition on Tungsten Substrate Young-Soon Kim, Jiho ShinQ, Hyung-Il Kim, Joong-Hee Cho, Hyung-Ki Seo, Gil-Sung Kim and Hyung-Shik Shin School of Chemical Engineering, Chonbuk National University, Dukjin-dong 1 Ga,GDuckjin-gu, Jeonbuk , Korea *Korean Minjok Leaders Academy, 1334 Sosa-rhee, Anheung-myun, Hoengsung-gun, Kangwon-do , Korea OReceived 27 December 2004; Accepted 15 April 2005) k h r nkp pn l vr dš(tungsten, W) Ž ol m. nkp CuSO g/l, EDTA g/l, glyoxylic acid 7 g/l m. nkp ph 11.0l 12.8 v e p, n kp m 60 o C ov m. p p s o l X r, r t rq, t oq, X rq Rutherford backscattering spectroscope(rbs) n m. p o q sp ph s p 11.8pm. p nkl 10 k n kp pq p lp, peakp l peakpm, r k 11 nm l., ph 11.8l 12 k p 140 nmpl k 12 nm/minm. r nkp ph 12.8 v e ˆ p Cu peak pnl peakp Cu 2 O ˆ pq k v kp m. p p o nkl r ph ov lk. p RBS r 99 atomím., Cu/W p r k ˆ p l r sk. Abstract Copper was plated on the tungsten substrate by use of a direct copper electroless plating. The optimum deposition conditions were found to be with a concentration of CuSO g/l, EDTA of g/l, and glyoxylic acid of 7 g/l, respectively. The solution temperature was maintained at 60 o C. The ph was varied from 11.0 to After the deposition, the properties of the copper film were investigated with X-ray diffractometer (XRD), Field emission secondary electron microscope (FESEM), Atomic force microscope (AFM), X-ray photoelectron spectroscope (XPS), and Rutherford backscattering spectroscope (RBS). The best deposition condition was founded to be the solution ph of In the case of 10 min deposition at the ph of 11.8, the grain shape was spherical, Cu phase was pure without impurity peak (Cu 2 O peak), and the surface root mean square roughness was about 11 nm. The thickness of the film turned out to be 140 nm after deposition for 12 min and the deposition rate was found to be about 12 nm/min. Increase in ph induced a formation of Cu 2 O phase with a long rectangular grain shape. The ph control seems to play an important role for the orientation of Cu in electroless deposition. The deposited copper concentration was 99 atomic percent according to RBS. The resulting Cu/W film yielded a good adhesive strength, because Cu/W alloy forms during electroless deposition. Key words: Copper Electroless Deposition, Tungsten, Glyoxylic Acid 1. ~ p o rrp (ITRS, international technology roadmap for semiconductor[1])l, 22 nmm 45 nm To whom correspondence should be addressed. hsshin@chonbuk.ac.kr p ULSI(ultra-large scale integrated) ql qp q p k p p r r p rqp p ~ lk, v l l v p. p rp v p PVD(physical vapor deposition) CVD(chemical vapor deposition) p ~ ql v eˆ l. 495

2 496 m Ëev Ë pëst Ë Ë Ëe e pl IBMp Andricacos[2] 1999 v l r r p m, p p s (high aspect ratio) nm p patternp holel (void)p (seam)p v k (super-filling) bottom-up }n(fillup) p m. p p r p electronics packaging ll m r n l m. m, 300 mm waferl ˆrp p, p v p np p. p rp r p n or k (HCHO, formaldehyde) p. v k q p k p o, Honmam Shacham-Diamand p rp ~ glyoxylic acid n p rk p [3-4]. r l n orp k Cannizzaro pp ppˆ. Cannizzaro pp m sq l aldehydep q - o pp. Carbonyl groupl pr ˆ oq (α-ˆ oq)l oq v aldehyde m sq l q - o pp pl rl aldol pp ppˆ. α-ˆ oql vv k aldehyde m sq l q - o pp ppˆ p pp Cannizzaro p p. pp carbonyl groupp ~ p f eq. Cannizzaro benzaldehyde m sq l p, benzoic acid m benzyl alcoholp p }p p m l Cannizzaro pp m. p p l m op pl rp vrp, p v 2 sp p l ( É) pp α-ˆ l l sk k l p. v, k pe (1)l k q p, q 1 k m dd o. p p k qp m qp op el pl k mp rm. p rp m benzaldehyde, formaldehyde glyoxylic acid p. 2RCHO + OH Ë RCH 2 OH + RCOO (1) k r l p rp or n l mp, Shacham-Diamand or k e glyoxylic acid n l vr l m. pp glyoxylic acid or n nkl p pp ˆ e p [5-6]. Cu COOHCHO + 4OH Ë Cu + 2COOHCOO + 2H 2 O + H 2 (2) pp r rp mechanisml p p. k l glyoxylic acidp k e (3) p pl. COOHCHO + 3OH Ë COOHCOO + 2H 2 O + 2e (E o ox =1.01V) (3), p l e (4)m p Cu pmp op el pl. (E o = V) red Cu e Ë Cu (4) p v k Pt, Ag, Au Pd p ol [7]. v dšp n Pourbaix[8]l p o43 o k m l tl (WO 2 WO 3 )p 2 WO 4 pmp l p p l v p p [9]. l l r nkp n l lp dš ol vr l p s m. 2. nkl n ekp o p (CuSO 4 5H 2 O), chelating agent ethylenediamine-tetraacetic acid(edta, C 10 H 16 O 8 N 2 ), or glyoxylic acid(coohcho) n m. p o v pnl ~ r ol kr p v eˆ o l polyethylene glycol 2,2-dipyridine l. CuSO 4 5H 2 O g/l, EDTA g/l, Glyoxylic acid 7 g/lp m. nkp ph 6N(Alfa aesar)p p tetramethylammonium hydroxide(tmah) ~ l 11.0l 12.8 v e. p nkp m 60 o C ov m. dš Žp e ml 10 k 99Í p k Šl pž } v rinse m. ph rp ml m. X-ray diffractometer(xrd) 30 kv, 20 mal Cu kα(λ= Ë) p n m, scan Bragg o 32 ol 60 5 /minp o m. e p s field emission scanning electron microscope (FESEM, JEOL JSM-6330F) s l. e p ˆ atomic force microscope(afm, Nanoscope IIIa, Digital Instruments/Veeco) 360 khzp tž tapping model s lp, reflex coating(detector side : Al-coating) e cantilever sensor n l r m. p p 10 nm p p p r. AFM rp tp eml r l. p ˆ s o l X-ray photoelectron spectroscope (XPS) n m. XPS } p base k p 3 4Ë10 torrmp 9 X-ray source Mg Kα( ev) n m. e p 4.0 MeV Dynamitron q Rutherford Back Scattering spectroscope(rbs) m r m. 3. y dš ol p s XRD mp Fig. 1l ˆ l. Fig. 1(a) dš Žl XRD patternp Fig. 2(b) ph 11.8 nkl 10 k p XRD peakp. Fig. 1(a) Novellus l DC-sputteringp v dš Žp ol W(100) peakm ol W(200) peak ˆ JCPDS card no.4-806p cubic sp q 3.153Ëp Žpp p pl. Fig. 1(b) d Š Ž ol p ol Cu(111) peakm ol Cu(200) peak ˆ JCPDS card no p cubic sp q 3.602Ëp lpp k p. p Cu peakp p[i(111)/i(200)]p 2.6pl, Cu(111)p FWHMp 0.21pl. r p card no.4-836p p 2.18 p pp, p l o Wang [6]p TaN ol r p p[i(111)/i(200)]p 2.8pl, Cu(111) peakp FWHMp 0.26

3 dš Žol r l l 497 Fig. 2. Plane view FESEM images of the W substrate and the Cu film deposited by electroless solution of ph 11.8, glyoxylic acid 7 g/l, 60 o C, 10 min. Fig. 1. X-ray diffraction of the W substrate and the Cu film deposited by electroless solution of ph 11.8, glyoxylic acid 7 g/l, 60 o C, 10 min. pl. Kennedym Minten[10] Young [11]p p Cu(111) p po p ƒ v p m. Fig. 2 Fig. 1l m p s p dš Ž(Fig. 2(a)) (Fig. 2(b))p plane-view FESEM p. Fig. 2(a)l dšp pq kp p p 100 nm p 10 nm p pq lt p. pm r p np Fig. 2(b)l pq ~r p p pq l pp nml 100 nm lt p. Fig. 3p Fig. 1l m p s p dš Ž(Fig. 3(a)) (Fig. 3(b))p AFM p vm Section analysisp. dšp n Fig. 3(a)l RMS (Root mean square(rms) roughness) 2nmmp, Fig. 3(b)l r p RMS Fig. 3. AFM images of the W substrate and the Cu film deposited by electroless solution of ph 11.8, glyoxylic acid 7 g/l, 60 o C, 10 min. Korean Chem. Eng. Res., Vol. 43, No. 4, August, 2005

4 498 m Ëev Ë pëst Ë Ë Ëe e Fig. 4. XPS spectra of the W substrate and Cu film deposited by electroless solution of ph 11.8, glyoxylic acid 7 g/l, 60 o C, 10 min. o43 o k

5 dš Žol r l l 499 k 11 nmm. Fig. 4 Fig. 1l m p s p dš Ž(Fig. 4(1)) (Fig. 4(2))p XPS d p. Fig. 4(1)-(a) dšp t d p W 4f, W 4d W 4p C 1sm O 1s sq, r rp XPS wide scan d p lt [12]. d Šp XPS narrow scanp Fig. 4(1)-(b) W 4fm W 5p d p 31 evl 38 ev vp l v l doublet separation p ˆ evm 35.8 evl ˆ l vp W 4f 7/2 W 4f 5/2 doublet separation p p WO 2 WO 3 pp k p, shake-up o (satellites)p ev l v W 4f 7/ evl p l v W 5p 3/2 pp k p. dšp W 4f 7/2m W 4f 5/2p d p l l p o W 4f 7/2 WOx p l l ˆ o [12-13]. Fig. 4(1)-(c) O 1sp d p fitting, ev p l v dš p WO 2m WO 3p l ˆ, ev l v O 2 p m p p l v ~r ppp k p. Fig. 4(1)-(d)p C 1s d p l v(c-c) ev v l t ˆ p t l vp. Fig. 4(2) r p XPS d p. Fig. 4(2)-(a) Cu 3p, Cu 2p O 1sm C 1s ˆ p r rp XPS wide scan d p. l 335 ev }l o peak p LMM Auger p. Fig. 4(2)-(b)p Cu 2p d p doublet separationp ˆ, ev(2p 3/2 ) m ev(2p 1/2 )p l vm doublet separation line ev XPS narrow scan d p., shake-up o (satellites) p Cu 2p 3/2m 2p 1/2p (intensities) evm evp o (satellite intensity). p p p CuO Cu 2 O l ˆ line p. Cu 2p d p doublet separation line 19.6 evp l v p Cu 2p 3/2 l v ev l mp m o [12]. Fig. 4(2)-(c)p O 1s d l ev l v p q rp l p p p pp, ev l v O 2p m p, dš Žl m v p l v ~r ppp lt p. Fig. 4(2)- (d)p C 1s d p l v ev v l t ˆ p t l v(c-c)m C-H l vp ev r p p p p. p r l p mr } v kk ˆ. Fig. 5 r p 8 (a, c) 12 (b, d) k ee e p plane-view(a, b)m cross-section(c, d) FESEM p v p. 8 k np Fig. 5(a) plane-view FESEM l d Š Ž ol p pp ~ v pq p v p s v kp p p. pm 12 Fig. 5(b)l p pq lp p s p p p. 8 k (Fig. 5(c) cross-section FESEM) Žl p 90 nmpl, 12 k (Fig. 5(d) cross-section FESEM) Žl p 140 nm r m. l 11.7 nm/minpp k p, prl Angal [9]l p or mol/lp formaldehyde n n 16.6 nm/minp Fig. 5. Plane view and cross-section FESEM images of Cu films versus deposition time (fixed ph 11.8, glyoxylic acid 7 g/l, 60 o C). rp p. Fig. 6p ph e p XRD p. Fig. 6(a) ph 11.0l n Cu 2 O peakp l Cu(111) peak p, ph 12.8 s p Fig. 6(b) l Cu 2 O peak p. Shacham-Diamandm Dubin[4], Lowenheim[14]p rk r pp k e (5)l m p q rp r 1 p pp qrp pl. 2Cu 2+ + HCHO + 5OH Ë Cu 2 O + HCOO + 3H 2 O (5), Zhang p n l p l p p Cu 2 O pp ƒ vp k m p y pe (6-8)p ˆ [15], Fig. 6. X-ray diffraction of Cu films versus solution of ph (fixed glyoxylic acid 7 g/l, 60 o C, 10 min). Korean Chem. Eng. Res., Vol. 43, No. 4, August, 2005

6 500 m Ëev Ë pëst Ë Ë Ëe e 4Cu + 2H 2 O Ë 2Cu 2 O + 4H + + 4e (anode) (6) O 2 + 2H 2 O + 4e Ë 4OH (cathode) (7) 4Cu + O 2 Ë 2Cu 2 O (net reaction) (8) Shu [16]p k e (9)m p pp pl l Cu 2 O p rk p. v HCHO or n, OH HCHOp o n v, k pe (9)m p Cupm r p l Cu 2 O. 2Cu(OH) 2 + 2H + + 2e Ë Cu 2 O + 3H 2 O (9) Kim [17]p nkp m m p p orp sr l p vp eˆ p p rk m. Cu p l Cu p o Cu 2 O p m p nkl r. p H 2 d p v m p v p l r p sv k. ol l pe(5-9) p p p OH m p p. l l ph 12.8 v eˆ, v OH p k v Cu 2 O p ˆ opp. l r l p l o rr php srp n p lt. Fig. 7p Fig. 6p s l php (ph 11.0(a), ph 12.8(b))l plane-view FESEM p vp. ph 11.0(Fig. 7(a))p nm p pq p l p p p p l, Fig. 2(b)p ph 11.8l 10 pq q pp k pl. ph 12.8(Fig. 7(b))p nl ˆ pq p l } l ppp p p l. Fig. 6(b)p XRDp l } Cu 2 O pp q pp l v pl p p v p p. p o RBS Fig. 8 p, dšp n MeV pl, p n 1.5m 1.6 MeV pl ˆ [18]. l l n dš Žp e Ž ol v p er p p oq e p np oq p intensity e l r p p l. pl RBS rp o Ž ol DC sputteringp pn l dšp v m, ol r p ee m. p s p Fig. 1(b)p s p ph mp Fig. 9l ˆ l. Ž ol v dšp RBS r p e m, dš ol p RBS v p e m Fig. 7. Plane view FESEM images of the Cu film versus solution of ph (fixed glyoxylic acid 7 g/l, 60 o C, 10 min). o43 o k Fig. 8. Relative yields and energies obtained for He backscattering from selected elements for an incident He energy of 2 MeV. Fig. 9. RBS spectra and XRUMP simulation of Cu film deposited for 10 min of solution ph 11.8 with glyoxylic acid concentration (0.09 mol/l) at a solution temperature of 60 o C on Tungsten/ Carbon film.. p o XRUMP [19]p n mp, dšp 480Ëpm, r p 1,140Ëpm. l (o )p ( ) p kp kk o Fig. 9p 0.4l 0.9 MeV p Fig. 10(a)l ˆ. l l p p kp 1Íp p Cu 2 O r v kp lpp p m., Fig. 9p 1.3l 1.9 MeV v Fig. 10(b)l ˆ l. dš Ž ol p v k nl XRUMP p n l e rp e (3) p ˆ p er r p RBS (1) p ˆ.

7 dš Žol r l l 501 pl. p, AFMp k 11 nmp, ph 11.8l 12 k p 140 nmp, k 12 nm/minpp p m. r nkp ph 12.8 v eˆ l Cu 2 O phase ˆ, pq k v kp l. pl r p ee np rr ph 11.8pp k pl. p RBS r 99 atomicí p pl., Cu/W p r k ˆ p k pl, p l r skv p k pl. l rl l( ) q r l (R )p vop p lr p pl. y Fig. 10. Extended RBS spectra from 200 to 400 channel of Fig. 9. simulation 300Ëp m dš p p pp p m. q pn n e p sp p p r l barrier p n, er barrier v p r p r p. pl ~ ll barrier v TiN, TaN WN p n p, p p r p r p s p p pl. 4. l l r nkl lp dš ol m. nkp o CuSO 4, chelating agent EDTA, or glyoxylic acid n m. nkp ph TMAH 11.0l 12.8 v e p, p nkp m 60 o C ov m. XRD r ph 11.8l l peakp llp, FESEMp ph 11.8l 10 k n kp pq p p p 1. International Technology Roadmap for Semiconductors (2003). 2. Andricacos, P. C., Copper on-chip Interconnections; A Breakthrough in Electrodeposition to Make Better Chips, The electrochemical Society Interface-spring, 32-37(1999). 3. Honma, H. and Kobayashi, T., Electroless Copper Deposition Process Using Glyoxylic Acid as a Reducing Agent, J. of the Electrochemical Society, 141(3), (1994). 4. Shacham-Diamand, Y. and Dubin, V. M., Copper Electroless Deposition Technology for Ultra-Large-Scale-Integration (ULSI) Metallization, Microelectronic Engineering, 33, 47-58(1997). 5. Shacham-Diamand, Y., Electroless Copper Deposition Using Glyoxylic Acid as Reducing Agent for Ultralarge Scale Integration Metallization, Eletrochemical and Solid-State Letters, 3(6), (2000). 6. Wang, Z., Ida, T., Sakaue, H., Shingubara, S. and Takahagi, T., Electroless Plating of Copper on Metal-Nitride Diffusion Barriers Initiated by Displacement Plating, Eletrochemical and Solid- State Letters, 6(3), C38-C41(2003). 7. Kim, J. J. and Kang, M. S., Fabrication of Cu Seed Layer on TiN Barrier Using Galvanic Displacement Deposition, HWA- HAK KONGHAK, 39(6), (2001). 8. Pourbaix, M., Atlas of Electrochemical Equilibria in Aqueous Solutions, Pergamon Press(1966). 9. Angal, M., Shacham-Diamand, Y., Mak, C., Miller, B. and Feldman, L., Self-Aligned Interconnects Made by Electroless Deposition of Copper on Tungsten, Proceedings-Electrochemical Society, 93(25), (1993). 10. Kennedy, R. M. and Minten, K., Growth Structures of Electroless Copper Films for Printed Wiring Boards, J. of Vacuum Science and TechnologyGB, 9(2), (1991). 11. Young, C. C., Duh, J. G. and Huang, C. S., Improved Characteristics of Electroless Cu Deposition on Pt-Ag Metallized Al 2 O 3 Substrates in Microelectronics Packaging, Surface and Coatings Technology, 145, (2001). 12. Moulder J. F., Stickle W. F., Sobol, P. E. and Bomben, K. D., Handbook of X-Ray Photoelectron Spectroscopy, Physical Electronics, Eden Praire(1992). Korean Chem. Eng. Res., Vol. 43, No. 4, August, 2005

8 502 m Ëev Ë pëst Ë Ë Ëe e 13. Sohn, J. R. and Bae, J. H., Characterization of Tungsten Oxide Supported on TiO 2 and Activity for Acid Catalysis, Korean J. Chem. Eng., 17(1), 86-92(2000). 14. Lowenheim, F. A., Modern Electroplating, 3rd. ed., John wiley & sons, New York, 734(1974). 15. Zhang, R., Gao, L. and Jingkun, G., Temperature-Sensitivity of Coating Copper on Sub-Micron Silicon Carbide Particles by Electroless Deposition in a Rotation Flask, Surface and Coatings Technology, 166, 67-71(2003). 16. Shu, J., Grandjean, B. P. A. and Kaliaguine, S., Effect of Cu(OH) 2 on Electroless Copper Plating, Ind. Eng. Chem. Res, 36(5), (1997). 17. Kim, J. J., Cha, S. H. and Lee, Y. S., Seedless Fill-up of the Damascene Structure Only by Copper Electroless Plating, Japan Journal of Applied Physics, 42, L953-L955(2003). 18. Baumann, S. A., Strathman, M. D., Steven, L. and Suib, S. L., Nondestructive Depth Profiling of Rare-Earth and Actinide Zeolites via Rutherford Backscattering Methods, Analytical Chemistry, 60, (1998). 19. Doolittle, L. R., Algorithms for the Rapid Simulation of Rutherford Backscattering Spectra, Nuclear Instruments and Methods in Physics Research Section B, 9(3), (1985). o43 o k