Particle Removal on Silicon Wafer Surface by Ozone-HF-NH 4

Korean Chem. Eng. Res., Vol. 45, No. 2, April, 2007, pp. 203-207 -jo- g g oi m lmœ Ž m mm o m Ç m (t)e l 730-724 e p 283 (2006 10o 18p r, 2006 12o 7p }ˆ) Particle Removal on Silicon Wafer Surface by Ozone-HF-NH 4 OH Sequence Gun-Ho Lee Gand So-Ik Bae R & D Center, Siltron, 283, Imsoo-dong, Gumi, Gyeong-Buk 730-724, Korea (Received 18 October 2006; accepted 7 December 2006) k h ms r e e op p pq rp r p r l l l m. p 0.3 vol% p p lk pq r lp, pž p ms n e r pp v l. ms r p l p(0.01 vol%) k k rp pq 99% p r p p m. p k k l p op p l m k mll p q v el qn l p p., -ms- k k rp p SC-1 r p m. -ms- k k rp ml pq rp r p r p, m r kp n s de rp kp. Abstract In this paper efficient method for particle removal from silicon wafers by usage of HF and ozone was studied. It was found that at least 0.3 vol% concentration of HF was required for particle removal and removal efficiency increased with the application of megasonic in ozonated water. Additional cleaning with minute amount of ammonia (0.01 vol%) after HF/Ozone step showed over 99% in removal efficiency. It is proposed that the superior cleaning efficiency of HF-Ozone-ammonia is due to micro-etching of silicon surface and impediment of particle re-adsorption in alkali environment. Compared to SC-1 cleaning method micro roughness has also been slightly improved. Therefore it is expected that HF-ozone-ammonia cleaning method is a viable alternative to the conventional wet cleaning methods. Key words: Wafer Cleaning, Ozone, HF, Particle Removal, Ammonia Water 1. e op op rs rp, q vrp o ~ rp v rl s mm l p p mm. p mm p ~ qp pp r eˆ opp l l(bare) e op p rs el CMP(chemical mechanical polishing) pn l r p l, ~ qp rs el mm p p o ~ r p l r rp ee l mm p rr tp rl lk. l e op p m qp (design rule)p r rp v l r rl n vp k v rp v p. pl, To whom correspondence should be addressed. E-mail: thisisho@siltron.co.kr ~ qp o v p, r rl p v } l np n p. m v o n e op r l RCA r p pp, r p mm p s l SPM(sulfuric acid peroxide mixture) DHF(dilute HF) ˆrp s l n. RCA r p p m p k p n m de rp, SC-1(standard clean 1) SC-2(standard clean 2)p [1]. SC-1p k k, (DI water)p kp n l m l v r rp op p pq r l ˆ o p p, SC-2 m, p kp n l k pm(al 3+, Fe 3+, Mg 2+ ) }p m m p r n p. v RCA r p mm v p r l p pp lp pp } e ˆ 203

204 p Ë p rp rn k } np p n, ml r rp v lk l v p p, p rk np p r np p n r p. pm p r o l de r rl ms p pn r p p p [2-4]. msp r f m p l p, n p p v k qrp v p. l n msp o mm, r, Cum p r l n rp p k r p [5-7]. p op p e p r n rp, p r rl pqm mm r l n rp. pq l p e p l rl r, p e l ˆ e r [8-11]. v p pn rp o l rp v l op p m (lift-off) pq e q rrp p [12]. rnk p e op p rˆ ro(zeta potential) nk p phl lp (-)ro v v, pq p nk p phl rˆ ro. p pq p k (alkali) mll (-)ro v o p p rr r p l p lr v, m ll pq p ro lr l (+)ro v rr r p p p pq p op p p p ov. p pn r l op p eˆ r q pq r rp e n. l l r op p eˆ o l ms n m, q pqp r m pq p q p v o l p k k pn r v l pq r pp v eˆ l m. 2. l l d pn CMP(chemical mechanical polishing) rl p l rp m v 200 mmp e op n m. op p pq SP1-Classic(KLA- Tencor)p n l r mp, (micro-roughness) AFM(PSI)p n l m., r contact angle meter ellipsometer(sopra) pn l m. e s e p Table 1 Table 2l ˆ l. Table 2p Test 1l ms r l pžp p o l pq r pp m. r ms r, r, ms r s r p v m. l n pžp tž 1 MHz(550 W) n m. Test 2l p l pq r pp m. r Test 1 p v m, ms r l pž n m. Test 3l Test 1 p r rp v, s v rl k k pn r v m. Normal s l p SC1p NH 4 OH:H 2 :H 2 O=1:2:40(at 55 o C)l 300 s k v p. 3. y 3-1. Megasonic r, e op p p l p l p rl p pqp p ov pq r l ov. op l p l p kr e k. e l (1 vol%) r, ms r v l op l p m. Fig. 1p r, ms r l p pž p o l pq r pp ˆ p. r ms r, r, ms r s v m. ms r l pž p l pq r pp 20%p eˆ pl. ms l pž p v k r mp p pq r pp 78.7%(2127 ; > 0.12 µm)m, pž p l r mp pq r pp 98%(200 ; > 0.12 µm) r pp v m. 3-2. j mm o l Fig. 2 r l p l pq r Table 1. Compositions and conditions of the cleaning solutions used in this experiment Name Ozone #1 Diluted HF Ozone #2 Diluted NH 4 OH Dry Chemical DIO 3 HF:DIW DIO 3 NH 4 OH:DIW DIW Mixing ratio 30 ppm 1:100(1 vol%) 30 ppm 1:10000(0.01 vol%) Process temp. 25 C 25 C 25 C 25 C 25 C Process time 300 s 300 s 300 s 300 s 60 mm/min Accessory Megasonic Megasonic Megasonic Table 2. Cleaning test methods for particle removal from silicon wafer surface Conditions Cleaning Sequences Test 1 Megasonic On/Off of ozone bath Ozone #1 HF Ozone #2 dry Test 2 Change of HF concentrations Ozone #1 HF Ozone #2 dry Test 3 Adding of diluted NH 4 OH step Ozone #1 HF Ozone #2 Diluted NH 4 OH dry Normal SC1 NH 4 OH:H 2 :H 2 O = 1:2:40 (at 55 C) SC1 Rinse dry o45 o2 2007 4k

-ms- k k rl p e op p pq r 205 Fig. 1. Influence of megasonic irradiation in ozonated water. (a) without megasonic, (b) with megasonic. Fig. 2. Dependence of particle removal efficiency on dissolved HF concentration in DI Water. pp ˆ p. l p 0.3 vol% p l pq r pp 90% pl. v p 0.3 vol% p l p l lp 98% p p p pq r pp m. p e p l rl op p pq r l rp pq r o p e p l p 0.3 vol% p p p l l plk. l e p l p p o l op p r p r m (Fig. 3). p 0.3 vol% p l op p e p l pl. v, p 0.3 vol% p l r p ms rl e p l v k l kppp p m. op p p l v k l pq r pp p p, Fig. 4. Etching rate of silicon oxide on dissolved HF concentration in DI Water. p 0.3 vol% p l p l l pq op p d r p. Fig. 4 p l e p l ˆ p. l p v e p l v m. e (1)l e p l (Å/min) p e l l p r r l e p l m. l, p e 1,000 Å r p. r p Ellipsometer pn l op r (49 Point)p r m. Etching Rate(Å/min) = ( p Oxide THK - t Oxide THK)/Time = l p r Oxide THK/Time (1) msp p q e p 15 Å n, 0.3 vol%p op p e p l eˆ l m. 3-3. g g (jo/ / g g o) Fig. 5 ms p pn r, k k r v mp pq r pp ˆ p. k k r v p f op p p q r pp 99.8%(26 ; > 0.12 µm)p v eˆ pl. p p op p l l p pq r m ph 9 p p k (alkali) mll p pq p lr el pl p p. r, ms r k k r v mp l k k l p op Fig. 3. Contact angle image of wafer surface on dissolved HF concentration in DI Water. Korean Chem. Eng. Res., Vol. 45, No. 2, April, 2007

206 p Ë p Fig. 8. Particle removal mechanism from silicon wafer surface. Fig. 5. Particle removal efficiency on addition of diluted NH 4 OH step. Fig. 6. Particle map of silicon wafer surface. (a) HF-NH 4 OH cleaning (ozone skip), (b) only diluted NH 4 OH cleaning (ozone and HF skip). p e p k (Fig. 6(a)). l p e p l op p p k k l p d p k pl. p pn r l op p passivation eˆ o rp rp. l l r ms r v pm p po p., ms r v k k k p r mp n, op p pq r pl (Fig. 6(b)). Fig. 7p k k l e p l ˆ p. ml 0.01 vol%p p k k l p e p l l. k k e k v l eˆ Fig. 7. Etching rate of silicon oxide on dissolved NH 4 OH concentration in DI Water. o45 o2 2007 4k l pp n n op p e p. op p p o l k k l p lk, e l 0.01~0.1 vol%p k k n m. l p e p l m kv, op p pq r q p v l m. Fig. 8p e p r l op p pq r ƒ vp ˆ p. l pq e op l p r rp v l p. p pq rp r o pqm r p v p r lk. p op p e p l n rp l op p d r p. v p o l r p v l r pq e q r p. op p eˆ q pq r o l ms k k rp l p r m. q pq op p r k p r p l p rl d r m. l p k k ~ rkp op p l eˆ l pq r m rkp k mlp l pqp q p v p l. Fig. 9 ms m k k pn l r, op p ˆ p. (a) normal s l p SC-1p r p op p p, (b) ms m p pn l r p op p p. (c) ms m k k pn l r p op p ˆ p. ms k k pn rp e op p l m p v kpp k p l. m, SC-1 r t p p lpp p pl. 4. ms re e op p pq rp r p l l l m. l, ~w, r msp pn r l ms l pž p pq r pp, w, p pn r l l p 0.3 vol% p p lk, w, r pp n v eˆ o l ms r p k k r pq r pp v, op ms rl p

-ms- k k rl p e op p pq r 207 Fig. 9. Micro-roughness and AFM Image of silicon wafer surface with cleaning methods. lpp p m. ms/ / k k r p rp ml, pq r ˆo s de rp kp p n p. y 1. Kern, W., Handbook of Semiconductor Wafer Cleaning Technology: Science, Technology and Applications, Noyes Publication, New Jersey(1993). 2. Ojima, S., Kubo, K., Kato, M., Toda, M. and Ohmi, T., Megasonic Excited Ozonized Water for the Cleaning of Silicon Surfaces, J. Electrochem. Soc., 144(4), 1482-1487(1997). 3. De Smedt, F., De Gendt, S., Heyns, M. M. and Vinckier, C., The Application of Ozone in Semiconductor Cleaning Processes: The Solubility Issue, J. Electrochem. Soc., 148(9), 487-493(2001). 4. Morita, M., Ida, J., Ii, T. and Ohmi, T., Proceeding of the IEEE International Symposium on Semiconductor Manufacturing Conference, 453(1999). 5. Vankerckhoven, H., De Smedt, F., Van Herp, B., Claes, M., De Gendt, S., Heyns, M. M. and Vickier, C., Determination of Photoresist Degradation Products in O 3 /DI Processing, Solid State Phenomena, 76-77, 207-210(2001). 6. Sang-Woo Lim and Christopher E. D. chidsey, Control of Ozonated Water Cleaning Process for Photoresist Removal, Solid State Phenomena, 76-77, 215-218(2001). 7. Claes, M., De Gendt, S., Kenens, C., Conard, T., Bender, H., Storm, W., Bauer, T., Lagrange, S., Mertens, P. and Heyns, M. M., A Control Deposition of Organic Contamination and the Removal with Ozone Based Cleanings, Solid State Phenomena, 76-77, 223-226(2001). 8. Choi, B.-K. and Jeon, H.-T., Removal of Cu Impurities on a Si Substrate by Using (H 2 +HF) and (UV/O 3 +HF), J. Korean Phy. Soc., 33(5), 579-583(1998). 9. Vos, R., Xu, K., Lux, M., Fyen, W., Singh, R., Chin, Z., Mertens, P., Hatcher, Z. and Heyns, M., Use of Surfactants for Improved Particle Performance of dhf-based Cleaning Recipes, Solid State Phenomena, 76-77, 263-266(2001). 10. Choi, G.-M., Yokoi, I. and Ohmi, T., The Role of Oxidant in HF- Based Solution for Noble Metal Removal form Substrate, Solid State Phenomena, 76-77, 267-270(2001). 11. Bergman, E. J., Lagrange, S., Claes, M., De Gendt, S. and Rohr, E., Pre-Diffusion Cleaning Using Ozone and HF, Solid State Phenomena, 76-77, 85-88(2001). 12. Knotter, D. M. and Dumesnil, Y., Particle Deposition Studies in Acidic Solutions, Solid State Phenomena, 76-77, 255-258(2001). Korean Chem. Eng. Res., Vol. 45, No. 2, April, 2007