REASONS FOR HEAT-RESISTANCE AND REDUCED OXIDE THICKNESS OF TA2N ANODIZED CAPACITORS

Ta2N anodized capacitors have much greater heat resistance than Ta ano dized capacitors. The difference between the heat resistances of the T a and Ta2N capacitors was investigated by Auger analysis and it was fo und that the Ta2N compound thin film itself has a high heat resistance : Very little thermal oxidation of this film occurs until relatively h igh temperatures. The thermal degradation of TaN2 anodized capacitors which takes place at temperatures above 450 degrees C was found to be due to the oxygen diffusion from the anodized layer to the Ta2N underl ayer, Another cause of thermal degradation was the oxidation of the Al electrode at high temperatures. Therefore, both the breakdown of the interface between the electrode and anodized layer and the oxidation o f Al also contributed to the thermal degradation of the capacitors at high temperature. Even though the thickness of the Ta2N anodized layer was reduced by using a 30 V anodizing voltage, the heat resistance wa s greater and the capacitance was 3 times as high as that of Ta capaci tors anodized at 160 V.