Sol-gel processed Y₂O₃ embedded capacitor based physically unclonable function

Physical unclonable function (PUF) can create unique signatures for each manufactured microelectronics system, utilizing the random variations during microfabrication. It has been reported that the natural physical randomness of nanomaterials or nanostructures can be a unique source of variation while fabricated at low temperatures. In this work, we suggest that the natural randomness of the sol-gel coating method of a high-k dielectric nanofilm can be used as the source of electrical PUF methodology. We embedded sol-gel processed yttrium oxide (Y₂O₃) film into insulator layers forming thin-film capacitors. Because of the morphological variation of the sol-gel processed Y₂O₃ film, device-to-device variation of the permittivity naturally occurred, resulting in more variation of the capacitances and thus improved PUF uniqueness. For electrically read-out of PUF information, we integrated the capacitor PUFs into thin-film transistors (TFTs), confirming significantly more variation of the drain current in the subthreshold region of the TFTs with the embedded Y₂O₃ sol-gel film. With the solution processibility and low-temperature processing used in this work, the PUFs in this work can be integrated into the backend-of-the-line of CMOS integrated circuits or flexible electronics for enhanced security functionalities in the distributed sensors and wearable/biomedical electronic devices.