Study of Electrical Probing through Thin-film Encapsulation Made of Al_2O_3 Films Deposited by Low Temperature ALD onto Different Metallic Underlayers

摘要

A qualitative study of electrical probing through 25 nm thick amorphous Al_2O_3 barrier layers, made by low temperature ALD, has been developed. It has been found that the effectiveness of probing depends on the metallic layer beneath the oxide barrier. While a 100 nm thick Cr layer does not allow any probing through the oxide, softer metals like Al turn out to be ideal candidates. From a mechanical point-of-view, nano-indentation studies (normal nano-indentation with a Berkovitch indenter) onto Al_2O_3 films made onto the different metals reveal that their mechanical properties are different. While Al_2O_3 onto Cr is very stiff, Al_2O_3 deposited onto Al is softer, allowing electrical probes to reach the metal underneath.