Complex three‐dimensional patterned oxide thin film physical authentication tags obtainable with a mass production scalable, highly multiparameter dependent combinatorial process

Chemical beam vapor deposition combined with the use of shadow masks is a versatile technique to deposit patterned multifunctional (in terms of thickness levels and chemical composition) oxide thin films. In this paper, the methodology and the results related to thin film patterning are presented through a use case where such thin films are used as identity tags for connected devices. The system relies on the reading of one or more material properties of the tag affixed to the object that must be combined with a secure authentication protocol. The measured properties have a twofold dimension: first ones are deterministic and based on submillimeter scale patterns (i.e. they can be predicted knowing exact deposition conditions of the tag) while the others are totally random due to unpredictable sub‐micrometric growth patterns. This allows the tags to be either exploited as a standard unique identifier (with enrollment) or based on a twin tag comparison (considering only deterministic properties). Due to the large number of deposition parameters and properties associated to each tag, they are unique, unclonable and secured from reverse engineering. A first reading prototype based only on film transmission reading at different wavelengths is also presented.