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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3.4.3 <strong>Effect</strong>s <strong>of</strong> PMA <strong>for</strong> Platinum Upper ElectrodesIn <strong>for</strong>mer section, PMA with gold upper electrodes were investigatedin order to be compared with PMA with aluminum upper electrodes.Consequently, PMA with these two metal electrodes showed quite differentbehavior after PMA, and also PDA. And although VFB was recovered almostcompletely by PMA at 300 o C <strong>for</strong> 10 minutes in nitrogen ambience in the case<strong>of</strong> aluminum upper electrodes, a recovery <strong>of</strong> VFB shift was not realized by anyannealing in the case <strong>of</strong> gold upper electrodes. From these results, it isconceivable that some reaction between aluminum and <strong>La</strong>2O3 would lead tothe recovery <strong>of</strong> VFB shift, and also a decrease <strong>of</strong> capacitance value. In orderto corroborate this supposition, another metal electrode except aluminumshould be examined. In my study, PMA with platinum upper electrodeswere investigated and these results will be described the following pages.3.4.3.1 Dependence on the Temperature <strong>of</strong> PMA with PlatinumUpper ElectrodesFirstly, dependence on the temperature <strong>of</strong> PMA with platinum upperelectrodes <strong>for</strong> <strong>La</strong>2O3 thin films was investigated same as other metalelectrodes. Figure 3-52 shows the C-V characteristics dependent on thetemperature <strong>of</strong> PMA <strong>for</strong> <strong>La</strong>2O3 thin films with platinum electrodes. Here,all <strong>of</strong> samples were HF-last treatment and annealed in nitrogen ambience <strong>for</strong>10 minutes. <strong>Annealing</strong> temperature from 300 o C to 600 o C was examinedrespectively. It was observed that the excellent C-V characteristic withoutany hysteresis and much VFB shift was observed by PMA at 300 o C. However,the degradation <strong>of</strong> the C-V characteristics such as an appearance <strong>of</strong>hysteresis classified into charge infection type or a decrease <strong>of</strong> capacitancevalue were also observed with increase in the temperature <strong>of</strong> PMA withplatinum 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 platinum upper electrodes. Here, the results<strong>of</strong> as-deposition and PDA were shown in same graph. It was found thatPMA with platinum upper electrodes increased the value <strong>of</strong> EOT withincrease in annealing temperature even though the value <strong>of</strong> EOT in the case- 75 -
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