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1 Jurnal f the Krean Ceramic Sciety Vl. 46, N. 1, pp. 10~15, Refractive Index Dispersin f Sputter-Depsited Silicn-Rich Silica Thin Films Byeng Kyu Jin and Yng Gyu Chi Department f Materials Science and Engineering, Krea Aerspace University, Gyenggi , Krea (Received July 7, 2008; Revised Nvember 26, 2008; Accepted December 3, 2008) rl g e ³Á ³ w wœ w wœ œw ( ; ; ) ABSTRACT We have fabricated silicn-rich silica thin films via RF magnetrn sputtering using a SiO target. Thickness evlutin and micrstructure change f such SiO x (1< x<2) films were investigated in terms f the substrate temperature during the depsitin. Optical interference patterns btained frm a spectrscpic reflectmeter were analyzed t yield refractive index dispersin prfiles f the depsited film layers in the visible wavelengths. Changes f the refractive indexes were then explained in cnnectin with changes in micrstructure and cmpsitin f the silicn-rich silicn xide films. Increase in the number f the Si-Si bnds frmed inside the SiO x thin films turned ut t be mainly respnsible fr the increase f refractive index. Key wrds : Silicn-rich silica, Thin film, Refractive index, Sputtering 1. Ÿw w sƒ w š w wù. q p» q w w, Ÿ j» w. w w ƒ l» Ÿ p j w e.,» z w»» ƒ w w y Ÿ p y w. 1,2) wr, j Ÿw w w. s q e q w w w ƒ q xk j» w w. 3,4) Ÿw w w j» z w l œ y w w. Crrespnding authr : Yng Gyu Chi ygchi@kau.ac.kr Tel : Fax : g»q x e t silicn-ninsulatr xk z y g» q,»» sww silicn phtnics w y š. g e ƒ 5,6) f w q š, œ x ƒ š» e» q j» e w ƒ Ÿ w. 3,4) j» e j w y. g» j ƒw ù e j w ù, ƒƒ ³ w ƒ wš œ y w w v w. k g yw y k silicn-rich silicn xide (SRSO) wš œ q wš w. SRSO w yw», 7-10), g 11) 12,13) rl 14,15) w š. rl k w vw, g 16,17) 10

2 e wš» CMOS œ w ƒ. rl w SRSO w g k» j w ù g e k w. ù w œ ƒ ƒw š x y ƒ v w. w rl œ w SiO k y w SRSO w,»q y w Ì y w q wš w. SRSO w» šƒ ù, 18-21) w p rl SiO x (1 x 2) w š w k. 2. x»q (100) w ƒ g(siltrnix C.) y w px nx g»q w ywš w.»q mm 2 w z m ƒƒ 40 q wš ƒ w»q t w w. v w k 99.9% SiO(Super Cnductr Materials C.) w. ü œ» œ Trr w š ƒ 15 sccm w œ œ Trrƒ w. v x š q» 150 W w w š œ 2 w»q 8z z k Ì ³ š w. k œ w w»q 50 C l 400 C¾ 50 C y j»q SiO x v w. ƒ v» 900 C 60 w z þw. g y 700 C w, w œ 22) e v Si SiO 2 swwù k q. Ì y w x x (JEOL, JSM-6700) y w, Ÿ x d»(spectrscpic reflectmeter; K-MAC C., ST2000DLXn) w 400~900 nm t w w w rp d w. w Si-Si w y w» w t y Ÿ»(FTIR; Perkin Elmer, Spectra 100) w rl g e 11 Fig. 1. Thicknesses f SiO x films pltted as a functin f substrate temperature. 450~1500 cm 1 d w. 3. š 3.1. Ì y»q ̃ yw, y w» w x x mw ƒ v Ì d w. d z s³e w Fig. 1 ùkü. SiO x Ì»q ƒ 50 C 250 C¾ ~215 nm ~124 nm w š z 400 C¾ ~253 nm ƒw.»q ƒ ü»wš v ü š y ƒ j. w š y 23) ƒ k w š ƒ w ƒw. ù»q ƒ ƒw»q w., k»q ƒ»q ƒ w w. x»q 24) 250 C¾ ̃ w ̃ ƒw ƒ j» y»q ƒ e w y w» w x x w d w. t SiO x 46«1y(2009)

3 진병규 최용규 12 Fig. 3. Particle sizes f SiOx films pltted as a functin f substrate temperature. 의 변화는 증착되는 입자의 이동 및 재증발(re-evapratin) 등을 야기하게 되고 이는 증착되는 박막의 두께 및 미세 구조에 영향을 주고 있음을 확인할 수 있다. 박막 내 입자는 박막에 조사되는 빛의 산란을 유발하고 따라서 입자크기의 변화와 같은 미세구조의 변화는 주요 광학적 특성 중 하나인 산란 강도의 변화를 야기한다. 특 히 입자의 크기가 조사되는 빛의 파장에 비해 약 1/10 정 도일 경우 레일라이 산란이 주로 발생하게 된다. 본 연구 에서 굴절률의 측정에 사용된 분광형 반사측정기의 파장 대역은 가시광(400~900 nm) 영역이었으며, 이러한 파장 은 제작된 SiO 박막의 입자크기보다 10배 이상 크기 때 문에 입자에 의한 레일라이 산란이 발생할 것임을 확인 x Fig. 2. FE-SEM micrgraphs f the SiOx films fr substrate temperatures f (a) 50C, (b) 250C, and (c) 400C. 박막 샘플의 사진을 Fig. 2에 도시하였다. 이러한 전계 방 출형 주사전자현미경 사진을 이미지 분석 방법을 통해 각 SiO 박막을 구성하는 입자의 평균크기를 구하였으며, 그 결과를 기판온도의 함수로써 Fig. 3에 나타내었다. 박막 내 입자의 크기가 박막의 두께가 감소하면서 커지는 것 을 알 수 있으며, 이는 기판의 온도가 증가하면서 박막 내 입자의 이동도가 증가하게 되고 그에 따라 입자의 밀 집성이 증가하여 입자의 크기가 조대화되는 것으로써 설 명될 수 있다. 반면 특정 온도 이상에서는 입자의 이동보 다 상대적으로 증착되는 양이 많아 입자의 이동이 쉽게 이루어지지 못해 입자의 조대화가 어렵다. 본 연구에 서 제작된 SiO 박막의 경우 250 C를 경계로 입자크기의 변화 경향이 바뀌는 것을 볼 수 있으며, 이러한 경향성은 박막의 두께 변화와 정확히 일치하고 있다. 즉, 기판온도 x 25,26) x 한국세라믹학회지 Fig. 4. Relative Rayleigh scattering intensities f the SiOx films pltted as a functin f substrate temperature.

4 w. j» y y y w d e w q w» w y w. 27) rl g e 13 9π 2 V 2 I s I d 2 λ 4 ( m 2 1) m 2 2 = [ ( + 2) ]2 ( 1 + cs θ )» V d ƒƒ v w v Ì ùkü, λ v q. θ m ƒƒ ƒ. ƒ v w Fig. 4 w. j»ƒ ƒ j»q 250 C v ƒ ƒ j y w, Fig. 3 Fig. 4 mw ƒ ü j» y w w ƒ Ÿx d»»q w ƒ w ùkù ql xk Ì w y w., w txw. 2π R A+ Bcs ( n ik)d λ» R A B, n k ƒƒ Ÿ w. 28) Ÿx d» d ƒ v ql x d w v Ì w ƒ Ÿ ƒ SiO x w, Fig. 5 w. w w 400 nm 700 nm Fig. 6 ùkü. q f x p ùküš ù w ƒ.» (2)» w ƒ Ÿ ƒ 10 w j ùkû» 18 g ƒ w w g w. B n n( λ) = A n λ 2 C n λ 4» A n, B n C n g w, SiO x g A n SiO 2 g A n (1.458) SiO g A n (1.860) ƒ (1) (2) (3) Fig. 5. Refractive index dispersin spectra f the SiO x film fr substrate temperature f (a) 50, 100, 250, 300, and 400 C, (b) 200 C, (c) 350 C, and (d) 200 C. Fig. 6. Refractive indices f the SiO x film at (a) 400 nm and (b) 700 nm pltted as a functin f substrate temperature. Squares and circles represent refractive indices at 400 nm and 700 nm, respectively. y. ƒ w j» y w y w w, y». d ƒ w w e q w. w» q w w»,»q w j» Ì y w. j w dw 46«1y(2009)

5 14 ³Á ³ Fig. 7. Representative FT-IR transmittance spectrum f a SiO x film. Nte that this film was fabricated under the substrate temperature f 50 C., y w» w t y Ÿ» y w ƒ n rp d w.»q n rp d wš, z n rp d w g»q w w. t v n rp Fig. 7 w.»q z Ì z w z n rp ƒ w vj w w, w w y w. Fig. 7 w rp ~ 610 cm 1 ùkù Si-Si w w, 29) ƒ v w vj w Fig. 8 w. Si-Si w ƒ f w, w w ƒ SiO x g w ƒw w» g ä SRSO w y w. wr, w e w ƒ v w œ e Fig. 2 y w»œ ùkü» y y j ù, ƒ v w. w SiO x SiO 2 SiO š rp 30) Si-Si w y», 1< x <2 w. t v w EDS mw y. Fig. 8. Refractive indices at 400 nm f the SiO x films pltted as a functin f relative amunt f the Si-Si bnds present in each SiO x film. 4. SiO k w p rl SiO x (1< x <2) w,»q y Ì j»ƒ y ƒ y w. Ÿ x d» d w SiO x»q w, w Si- Si w w q. w g w w x y w. Acknwledgments 2006 w w w (KRF D00238). REFERENCES 1. S. V. Bhat, A. Gvindaraj, and C. N. R. Ra, Tuning the Emissin Bands f Nanphsphrs Thrugh the Refractive Index f the Medium, Chem. Phys. Lett., 422 [4-6] (2006). 2. A. L. Lpez, M. A. Mijares, and O. Malik, Optical and Electrical Prperties f Silicn Rich Oxide Films fr Optical Sensrs, Sensr Actuatr. A, 132 [1] (2006). 3. D. M. Ye, and S. Y. Shin, Plymer-silica Hybrid 1 2 Thermptic Switch with Lw Crsstalk, Optic. Cmm., 267 [2] (2006). 4. M. C. Oh, C. Zhang, H. J. Lee, W. H. Steier, and H. R. Fet- w wz

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