STUDY ON THE INTERFACES OF CU PA-N AND PA-N/SI BY SECONDARY-ION MASS-SPECTROSCOPY AND SCANNING ELECTRON-MICROSCOPY/

For microelectronics applications, it is important to have good interf acial properties between copper and parylene-N (Cu/PA-N), and parylene -N and silicon (PA-N/Si). Two of the relevant interfacial properties s tudied in this article are diffusion of the individual layers into the other layer at application temperatures and adhesion between these la yers. The interface between copper and parylene-N, and parylene-N and silicon has been studied using secondary ion mass spectroscopy (SIMS). Scanning electron microscopy (SEM) has also been used to study the PA -N/Si interface. SEM revealed the microstructure at the interface. SIM S was used to tunnel through the composite film in the cross section a nd get the various elemental concentrations. This gave the average con centrations prevailing, at a particular depth. It was observed that co pper diffuses, from the top, through the PA-N film to the silicon subs trate at 350 degrees C. Gettering of copper was observed, leading to h igh concentration of copper at the Cu/PA-N and PA-N/Si interface. A hi gh distribution of silicon was observed in PA-N at the PA-N/Si interfa ce. X-ray photoelectron spectroscopy studies showed that no new chemic al bonds were formed. Thus, diffusion resulted in a mixing layer which led to good interfacial adhesion. (C) 1996 American Vacuum Society.