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

3.4.2.2 Effects of Chemical Oxidation Treatment for PMA withGold Upper ElectrodesThe effects of chemical oxidation treatment for PMA with gold upperelectrodes were investigated same as the case of PMA with aluminum upperelectrodes. Figure 3-40 shows the C-V characteristics of PMA dependent onthe annealing temperature in the case of chemical oxidation treatment.From rough view, the tendency for the effect of PMA appeared on chemicaloxidation treatment same as in the case of PMA with aluminum upperelectrodes, namely, an increase of the capacitance value with increase in theannealing temperature, and an increase of VFB shift to negative side withincrease in annealing temperature as well. To be precise, some effects ofchemical oxidation treatment were found from the comparison with HF-lasttreatment. Figure 3-41 shows the values of the EOT versus annealingtemperature plot for La2O3 thin films with gold upper electrodes as thesupplement to Figure 3-37. It was found that chemical oxidation treatmentslightly decrease the value of EOT as compared to the ones of HF-lasttreatment, but also a decrease of EOT was almost proportional to annealingtemperature. Figure 3-42 shows the values of the VFB shift versusannealing temperature plot for La2O3 thin films with gold upper electrodesas the supplement to Figure 3-38. This graph indicates that chemicaloxidation treatment for PMA with gold upper electrodes slightly enlarged theVFB shift toward negative side for same annealing temperature, but also VFBwas almost proportional to the temperature of PMA. Figure 3-43 showsEOT versus J plot for La2O3 MIS capacitor with gold upper electrodesfabricated by as-deposition, PDA and PMA as the supplement to Figure 3-39.It was found that chemical oxidation treatment decreased leakage currentapproximately 1 to 2 orders of magnitude as compared to HF-last treatment,and universal relation between EOT and leakage current was also observedsame as the case of HF-last treatment.- 65 -