Jurnal f the Krean Ceramic Sciety Vl. 46, N. 2, pp. 155~160, 2009. Thermally Stimulated Deplarizatin Current Test fr Reliability f X5R MLCC Ji-Yung Park, Jae-Sung Park, Yung-Tae Kim, and Kang-Hen Hur MLCC R&D Grup, LCR Divisin, Samsung Electr-Mechanics C. Ltd., Suwn 443-743, Krea (Received Nvember 14, 2008; Accepted December 9, 2008) TSDC w X5R MLCC sƒ Á Á½ káx x» LCR LCR q (2008 11 14 ; 2008 12 9 ) ABSTRACT The reliability culd be ne f the essential prperties fr multilayer ceramic capacitr (MLCC) using in varius electrnic devices and the cncentratin and mbility f xygen vacancy wuld play imprtant rle in the reliability. T investigate the migratin behavir f xygen vacancies, thermally stimulated deplarizatin current (TSDC) is adpted. In dielectric material f X5R MLCC, the TSD-Current peak bserved arund 150 C and 200 C which represented the migratin f xygen vacancy. Substituting Yttrium fr Dysprsium in X5R MLCC shwed higher migratin activatin energy and lwer TSD current density. Key wrds : Thermally stimulated deplarizatin current, TSDC, X5R, BaTiO 3, Reliability 1. w š IT»» xy, š y, y t y MLCC x, š y,. š MLCC x w w y yƒ w wƒš. sƒ w wƒš. TSDC (Thermally Stimulated Deplarizatin Current) ƒw k ü d w, œ, diple, œœ relaxatin w w. x trap 1,2) w w ü defect (diple, trap charge, mbile in ), s ƒ š. Ni-MLCC w w ƒ w parameter TSDC w, w y ƒ œœ y w. w mw Crrespnding authr : Ji-Yung Park E-mail : jiyung007.park@samsung.cm Tel : +82-31-218-2572 Fax : +82-31-210-6963 dw. TSDC x mw» lƒ w y f TSDC x sƒ ƒ w mw. 2. x X5R Ni-MLCC Dy Dy Y ƒ w r TSDC d w. x X5R š» š rare earth element Dy 2 O 3 ƒ» Y 2 O 3 š p w ù, w œ y. Dy+Y yw w p sƒ, Dy ƒ Dy+Y yw ƒ p w ù ƒ û. TSDC d mw Dy:Y 10:0, 6 : 4, 4 : 6, 0 :10 ƒw defect š d w. n TSG-mill (Amex, Japan) 7m/s 80 w w X5R MLCC y wwš n z 15 150 rpm Ball-millw 155
박지영 박재성 김영태 허강헌 156 극으로 사용하였다. 이 시편을 250 C까지 측정 가능한 Delta Chamber에 넣고, 시료에 인가하는 전압은 0-1100V 까지 가변할 수 있는 Keithley 237 기기를 이용하였고, 시 편으로부터 발생하는 열자극 탈분극 전류는 전류계(Keithley, 6517 electrmeter 또는 237 surce-measure unit)를 사용 하여 측정하였다. 먼저 시편 내에 이미 존재하고 있을 분극 성분을 제거 하기 위하여 시편의 온도를 200 C까지 올려 10분 동안 유 지한 다음, 인가전압 E 와 인가시간 t 를 선택하여 분극 시 킨 후 상온으로 급냉하였다(Fig. 1). 온도를 다시 상승시키 기 전에 인가했던 전기장을 제거하고 20분간 유지 후 전 극을 전류계에 연결한 다음 일정한 승온 속도(2.5 C/min) 로 온도를 올리면서 나타나는 탈분극 전류를 측정하였다. P P 3. 3.1. Literature 결과 및 고찰 Survey f Degradatin Resistance The Prcess f TSDC Technique : 1. hetercharge (= ppsite sign f the plarizing electrde), 2: cexistence f hetercharge and hmcharge(= same sign as plarizing electrde). 7) 성형 슬러리를 제조하였다. 대략 10 um 정도의 두께로 sheet를 성형한 후 적층, 압착, 절단 과정을 통하여 green 유전체 후판(~1 mm) 시편을 준비하였다. 이들을 400 C에 서 3시간 가소 한 후 P 1% 분위기 하에서 2시간 소성 후 재산화 처리하여 소결체 시편을 준비하였다. 소성된 유전체 시편 양면에 In-Ga paste를 도포하여 전 H2 Fig. 2. 한국세라믹학회지 Insulatin BaTiO 를 고온에서 소성 할 경우, 재료 내에 포함되어 있는 불순물이나 첨가물로 첨가된 dnr/acceptr의 농도 에 따라 그 농도가 달라지지만, 유전체 내 본질적으로 일 정 양의 산소결함(xygen vacancy, V )이 형성된다. 이 산 소 결함은 격자점에 상대적으로 + charge를 띠고 있어, 직 류 전계 하에서 cathde 쪽으로 전기적 migratin을 일으 켜 공간 전하 분극(space charge plarizatin)을 형성할 수 있다. 이 결과 결정 입계(grain bundary) 및 전극 계면 (electrde interface)에 강한 내부 전계(internal field)를 만 들고, 이에 따라 leakage current가 증가되어 절연파괴가 일어난다고 알려져 있다. Chazn 등 은, 전극 계면의 저항이 열화되는 것이 Ni-MLCC의 절연 열화와 관련이 있다고 보고하였다. Ni-MLCC chip의 임피던스 분석을 통 3 Fig. 1. f.. O 3,4) A Mdel fr the Degradatin f the Insulatin Resistance in BaTiO -based Ni-MLCC. 3 4)
TSDC w X5R MLCC sƒ 157 w cre, shell, grain bundary / (ceramic/ internal electrde interface) 4ƒ w w, / w ƒ Ni-MLCC w y š w., Fig. 2 Electric Fieldƒ ƒw» tunneling w ƒ xygen vacancyƒ (cathde) pass x w w. Bucci 5) x ³ w» w Inic Thermcnductivity (ITC) w. Fig. 1 1) r diple field E t jš, 2) inic mtin û û š field w z, 3) d w w 8) Fig. 3. (a)tsdc spectrum f undped BaTiO 3 (b) Typical TSDC spectra f dped-bt sample fr varius plarizatin times. 3). 6,7).» d peak w k sx k ƒ ùkù. TSDC (Thermally Stimulated Deplarizatin Current) w defect rientatin». ƒ hst in ey, lattice vacancyù interstitial hst in, impurity in defectƒ charge impurity in ƒ¾ diple cmplexƒ»š, diple TSDC. Huebner 8) undped-batio 3 TSDC tw, Fig. 3(a) x 3 TSDC peak. undped-batio 3 sharp peak w current ƒ š. Ni-MLCC p w acceptr/dnr ƒw dped-batio 3 w Takeka 2) TSDC p šw. Fig. 3(b) peak 2.» y d shrtcircuiting k, y w w d w w» Fig. 4(b) peak š ùkù space charge w peak š w. w peak α saturatin š peak β ƒw ƒw, w w peak β ƒ w š w. w œœ w š peak β x w current, peak α œœ grain ü relaxatin w š w. 3.2. TSDC f Dy+Y in X5R X5R r TSDC d w d x w. TSDC peak y w» w (T P ), (t P ), (E P ) yw d w. Fig. 4 y peak yw. Fig. 4(a) y ƒ ƒ j. ù 80, 150 C 1V/um 10 w w peak š 250 C w x (25 C ~ 250 C) š peak. y g (Fig. 4(b)), g ƒ. y g (Fig. 4(c)) TSDC 46«2y(2009)
158 Á Á½ káx x ƒ w. plarizatin ƒ ƒw TSDC peakƒ ƒw, x space charge w X5R l œœ relaxatin w š. Fig. 4(c) 200 C 1V/um w TSDC peak 150 C peak (peak α) wš(saturatin š) 220 C peak (peak β) ¼ ƒ w f., w peak α œœ grain ü w relaxatin peak š, ƒw peak β œœ grain w relaxatin peak š ƒw. d TSDC peak l œœ activatin energy w fitting w. 4,9) In J( T) ---------------- Cnst. E = ----- + exp kt E -------- ----- kt m E kt (1) Fig. 4 TSDC peak w activatin energy w Fig. 5 ùkü. Fig. 4(c) TSDC peak activatin energy ƒ peak w (Fig. 5 #5 ~ 8). Fig. 4 Fig. 5 plarizatin (,, ), e peak activatin energy ƒ. k TSDC x peak ƒ (Dy+Y in X5R, TP = 200 C, EP =1 V/um, tp =10 ) š w. Fig. 4. TSD-Current with varius plarizatin cnditins (a) Plarizatin Temperature (T P ) at 80, 150, 200, 250 C, (b) Electrical Field (E P ) with 1 V/um, 0.5 V/um and (c) plarizatin time (t P ) at 10, 15,30 and 50 min. Fig. 5. Activatin Energy (ev) f TSD-Current peak with plarizatin cnditins : 1-T P ;200 C, 2-T P ;250 C, 3- E P ;1 V/um, 4-E P ;0.5 V/um, 5-t P ;10 min, 6-t P ;15 min, 7- t P ;30 min, 8-t P ;50 min. w wz
TSDC w X5R MLCC sƒ 159 TSDC peak w activatin energy w k X5R k w Dy+Y y w x T P =200 C, E P =1 V/um, t P =10 š w. ƒƒ TSDC d w Fig. 6(a) ùkü. x, Dy/Y w sample ƒƒ 150 C peak (peak α) 220 C peak (peak β) ùkû, peak max (Tmax) (Jmax) w TSDC pattern.», ƒ w k z d w» ƒ peak max ƒ., TSDC j defectƒ š w. Fig. 6(c) ƒ peak w e(jmax) Fig. 6(b) activatin energy j». ƒ peak Jmax activatin energy(ea) w Fig. 6(b), (c) Dy100, Y100 Dy+Y sample Eaƒ š Jmaxƒ. Jmaxƒ defectƒ š w w. Eaƒ û œœ plarizatin, plarizatin œœ relaxatin w w, Eaƒ š dw., k Dy+Y yw Dy, Y š dw. Dy+Y yw Dy X5R MLCC chip ƒ test ew. chip Dy100 Dy50 +Y50 MLCCƒ w ƒ p., TSDC d w activatin energy d w sƒƒ q w. 4. Fig. 6. Sample with the cmpsitin f Dy100, Dy60, Dy40, and Y100 (a) TSD-Current, (b) calculated activatin energy, and (c) maximum current density(jmax) at peak α and peak β. X5R MLCC Dy Y 0, 40, 60, 100% eyw r TSDC d w. X5R w 150 C 200 C peak œœ y w. Dy+Y y x Dyù Y w Dy+Y yw œœ»w activatin energyƒ š defect ƒ û q. Dy50-Y50 chip ƒ x ew. k Dy Y ƒw, p ww 46«2y(2009)
160 Á Á½ káx x š q ƒ w. k TSDC x sƒ ƒ w mw TSDC TSDC x, activatin energy mw q» ƒ w š ƒ. REFERENCES 1. C. Lavergne and C. Lacabanne, A Review f Therm- Stimulated Current, IEEE, Electrical Insulatin Magazine, 9 [2] 5-21 (1993). 2. H.J.Sng, Y.R.Lee, and Y.J.Park, Study n Plarizatin Prperties f BaTiO 3 by Using Thermally Stimulated Deplarizatin Current(in Krean), Kr. J. Mat. Res., 12 [8] 613-16 (2002). 3. S.Takeka, K.Mrita, Y.Mizun, and H.Kishi, Thermally Stimulataed Current (TSC) Studies n Resistance Degradatin f Ni0MLCC, Ferrelectrics, 356 [1] 78-84 (2007). 4. H. Chazn and H. Kishi, dc-electrical Degradatin f the BT-Based Material fr Multilayer Ceramic Capacitr with Ni internal Electrde : Impedance Analysis and Micrstructure, Jpn. J. Appl. Phys., 40 5624-29 (2001). 5. C. Bucci and R. Fieshi, Inic Thermcnductivity. Methd fr the Investigatin f Plarizatin in Insulatrs, Phy. Rev. Lett., 12 [1] 16-9 (1964). 6. J.Jung and Ph.D.Thesis, Defect Chemistry and Electrical Prperties f BaTiO 3, pp.109-119, Sungkyunkwan Univ., (2005). 7. P.Braunlich, Thermally Stimulated Relaxatin in Slids, Vl. 37, pp.69-93, Tpics in Applied Physics, Springer-Verlag., (1979). 8. W.Huebner, Thermally Stimulated Current and Dielectric Prperties f Dped and Undped Barium Titanate, Ph.D. Thesis, Univ. Missuri-Rllar (1987). 9. F.El Kamel, P.Gnn, F.Jmni, and B.Yangui, Thermally Stimulated Currents in Amrphus Barium Titanate Thin Films Depsited By Rf Magnetrn Sputtering, J. Appl. Phys., 100 054107-1-054107-6 (2006). w wz