Modifying the native aluminum oxide layer by simple methods for fabricating write-once-read-many memory devices
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abstract
In this work, we have fabricated write-once-read-many (WORM) memory devices based on the modification of the native aluminum oxide (AlOx) layer of the aluminum (Al) bottom electrode using different approaches, such as irradiation of a UV-ozone(UVO) cleaner for 5 min (AlOx-UVO), the exposure for a few seconds of the native AlOx to a 1 M solution of oxalic acid (AlOx-OA) and a combination of treatment using the UVO cleaner and the exposure to an oxalic acid solutio (AlOx-UVO-OA). We found that with the different treatments of the native AlOx, the physical, chemical, and electrical properties of the insulating layer of the Al/AlOx/Al WORM devices are different. WORM devices based on the AlOx-UVO and AlOx-OA layers showedanON/OFF ratio of* 1 9 102,while those based on the AlOx-UVO-OA layer showed an ON/OFF ratio of * 1 9 104. Furthermore, despite presenting a thin insulating layer (B 4 nm), the devices did not reveal the presence of physical deformations on the top electrode. The absence of physical deformations indicates that the electrical switching mechanism is not based on an anti-fuse mechanism, suggesting that the mechanism corresponds to a soft dielectric breakdown related to the creation of oxygen vacancies, with the consequent conductive filamentary paths in the AlOx layer.
