Effect of Post Metallization Annealing for La 2 O 3 Thin Film
Effect of Post Metallization Annealing for La 2 O 3 Thin Film
Effect of Post Metallization Annealing for La 2 O 3 Thin Film
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3.4.2 <strong>Effect</strong>s <strong>of</strong> PMA <strong>for</strong> Gold Upper ElectrodesFrom the investigation <strong>of</strong> PMA with aluminum upper electrodes <strong>for</strong><strong>La</strong>2O3 thin films, it was found that VFB was recovered to positive side by PMA.However, it was not clear that the reasons <strong>of</strong> that recovery <strong>of</strong> VFB wasowing to the PMA itself, covering <strong>La</strong>2O3 thin films with metal electrodesduring thermal process, or some reactions between <strong>La</strong>2O3 and aluminum as aresult <strong>of</strong> annealing with contact one another. Hence, PMA with anotherupper electrode should be investigated.In order to clarify the mechanism <strong>of</strong> the effect <strong>of</strong> PMA, PMA with goldupper electrodes was investigated.3.4.2.1 Dependence on the Temperature <strong>of</strong> PMA with Gold UpperElectrodesFirstly, dependence on the temperature <strong>of</strong> PMA with gold upperelectrodes <strong>for</strong> <strong>La</strong>2O3 thin films was investigated. Figure 3-36 shows the C-Vcharacteristics dependent on the temperature <strong>of</strong> PMA <strong>for</strong> <strong>La</strong>2O3 thin filmswith gold upper electrodes. Here, all <strong>of</strong> samples were HF-last treatmentand annealed in nitrogen ambience <strong>for</strong> 10 minutes. <strong>Annealing</strong> temperaturefrom 300 o C to 450 o C was examined respectively. It was observed that PMAwith gold upper electrodes increased the capacitance value with increase inthe annealing temperature, but also increased VFB shift to negative side withincrease in annealing temperature in contrast with the case <strong>of</strong> PMA withaluminum upper electrodes.Figure 3.37 shows the values <strong>of</strong> EOT versus annealing temperatureplot <strong>for</strong> <strong>La</strong>2O3 thin films with gold upper electrodes. Here, the results <strong>of</strong>As-deposition and PDA were shown in same graph. It was found that adecrease <strong>of</strong> EOT caused by PMA was proportional to the annealingtemperature in the case <strong>of</strong> gold upper electrodes.Figure 3.38 shows the values <strong>of</strong> the VFB shift versus annealingtemperature plot <strong>for</strong> <strong>La</strong>2O3 thin films with gold upper electrodes. It wasfound that variations <strong>of</strong> the VFB shift caused by PMA were proportional tothe annealing temperature to negative side in the case <strong>of</strong> gold upperelectrodes. And a range <strong>of</strong> the VFB shift cause by PMA was less than the- 62 -
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