Effect of Post Metallization Annealing for La 2 O 3 Thin Film

3.4.1.4 Dependence on the Ambience of PMA with AluminumUpper ElectrodesThe influence of annealing ambience on the electrical characteristicsof PDA was already described. And up to this point, all of experiments interms of PMA were done fixed to nitrogen ambience. Then, the influence ofthe annealing ambience through PMA was examined same as PDA. Figure3-31 shows the C-V characteristics annealed in nitrogen, oxygen and forminggas ambience respectively. The any difference from nitrogen ambience,however, was not observed in the case of PMA. Figure 3-32 shows thecomparison of the C-V characteristics of PMA between nitrogen and oxygenambience on each annealing time from 0 second (spike) to 100 minutes. It isconfirmed that there was, roughly speaking, nothing different betweennitrogen and oxygen ambience. It can be considered that it is difficult forPMA samples to affect the ambience during the annealing because La2O3thin films are always covered with upper electrodes in the case of PMA, inother words, La2O3 films are not supposed to expose the atmosphere directlyduring annealing. This fact would make it difficult to exert an influence onthe electrical characteristics. Finally, the plots of VFB shift and EOT wereshown, as the supplements to Figure 3-29 and 3-30, in Figure 3-33 andFigure 3-34 respectively. From these Figures, it was found that there wasno influence on VFB and EOT owing to the annealing ambience and bothambience showed similar tendency.Capacitance (µF/cm 2 )1Al/La O / n-Si(100)/Al2 3250 o C depo HF-lastPMA 300 o C 10min.N , O 2 2& F/G ambientIdeal V FBAl_PMA_300C_10min._F/GAl_PMA_300C_10min._N2Al_PMA_300C_10min._O20-1.5 -1 -0.5 0 0.5 1Voltage (V)Figure 3.31: The C-V characteristics annealed in N2, O2 and F/G ambience- 57 -