Micromachining of Al2O3 thin films via laser drilling and plasma etching for interfacing copper

Abstract

Due to their chemical inertness and high-temperature stability, atomic layer deposited (ALD) oxide thin films emerged as an attractive copper encapsulation, passivation, and protection technology. Several types of high-k dielectrics, which are robust insulators, can be deposited by ALD. Hence, a successful encapsulation process electrically isolates the underlying film and active elements from the environment, as a side effect. To electrically interface such encapsulated structures, a reliable method that selectively and locally removes the encapsulation film is required. Here, the study focused on the effectiveness of laser drilling and plasma etching of Al2O3 thin films deposited via ALD, both in silico and experimentally. Results have shown that the CO2 laser drilling alone is insufficient to remove the Al2O3 thin films. However, plasma etching successfully removes the encapsulation layer, providing a clean interface for conductive vias. Results are essential for future ALD layer applications in the encapsulation of copper and other critical components in semiconductor fabrication processes.