유기금속화학기상증착법에 의한 ZnO:Al 필름 합성에서 플라즈마 인가 효과

Effect of Plasma Enhancement on the Al-doped ZnO Thin Film Synthesis by MOCVD

Abstract

Al-doped ZnO (AZO) thin films were synthesized on Si(100) wafers via plasma enhanced metal organic chemical vapor deposition (PE-MOCVD) method using diethyl zinc (DEZ) and N-methylpyrrolidine alane (MPA) as precursors. Effects of Al/Zn mixing ratio, plasma power on the surface morphology, crystal structure, and electrical property were investigated with SEM, XRD and 4-point probe measurement respectively. Growth rate of the film decreased slightly with increasing the Al/Zn mixing ratio, however electrical property was enhanced and resistivity of the film decreased greatly about 2 orders from $9.5{\times}10^{-1}$ to $8.0{\times}10^{-3}{\Omega}cm$ when the Al/Zn mixing ratio varied from 0 to 9 mol%. XRD analysis showed that the grain size increased with increasing the Al/Zn mixing ratio. Growth rate and electrical property were enhanced in a mild plasma condition. Resistivity of AZO film decreased down to $7.0{\times}10^{-4}{\Omega}cm$ at an indirect plasma of 100 W condition which was enough value to use for the transparent conducting oxide (TCO) material.

Fig. 1 Schematic diagram of a PE-MOCVD system

Fig. 2 SEM images of the films deposited in various Al/Zn ratios. (A) 0% (B) 3% (C) 6% (D) 9%

Fig. 3 Surface reflectance patterns

Fig. 4 Growth rate and resistivity vs Al/Zn ratio

Fig. 5 XRD patterns of the deposited films

Fig. 7 SEM images of the AZO films deposited in a plasma conditions(A) no plasma (B) 50 W (C) 100 W (D) 150 W : direct plasma (E) 50 W (F) 100 W (G) 150 W : indirect plasma

Fig. 8 Effect of plasma power on the growth rate

Fig. 9 Effect of plasma power on the resistivity

Fig. 6 Effect of Al/Zn ratio on the interplanar distance of (002) plane

Table 1 Experimental conditions