The influence of Al2O3 nanolamination in ALD ZrO2 capacitor on physical and electrical characteristics

In this paper, the nanolamination of a ZrO2 insulator by Al2O3 for metal insulator metal capacitor applications has been studied. The insulating layers (ZrO2 and Al2O3) were deposited by atomic layer deposition and the electrodes were made of TiN. Different configurations of ZrO2 and Al2O3 alternations were studied, including 1 to 16 Al2O3 inclusions in the ZrO2 layer. X-ray diffraction of the insulator configurations showed that with four or more Al2O3 inclusions, the structure loses its crystalline orientation and becomes amorphous. Electrical characterizations have been conducted to study the capacitance, breakdown field, and leakage current for every insulator configuration. The capacitance density significantly decreases as the number of Al2O3 layers increases, except when an amorphous transition occurs; at this point, a local maximum of 17 nF/mm2 was found. A 19% increase of the breakdown field of samples with two or more Al2O3 inclusions has been correlated with an increase of leakage current explained by the emergence of the Fowler–Nordeim conduction mechanism at electrical fields higher than 4 MV/cm.