Uniformity and characterisation of PVD aluminium films.

Aluminium is a very important material used in the semiconductor industry as an interconnection layer. The most popular method of depositing aluminium films is the physical vapour deposition (PVD) process. The objective of the present study is to improve aluminium film uniformity by optimising the process conditions to use a thicker target and meet the demand for more uniform films on wafer surfaces. Aluminium films were deposited by a sputtering process on 200 mm wafers in PVD chambers. Experiments were carried out to find the process factors that affect film uniformity. The results revealed that film uniformity was affected significantly by wafer to target spacing and process pressure. Film characterisation was then performed by measuring grain size and film surface roughness, and performing package level electron migration, ball shear and bond pull tests. A higher process pressure resulted in more uniform films with bigger grains, lower surface roughness, longer reliability lives and higher ball shear values. With optimised process conditions, the aluminium layer uniformity can be maintained at <1·5% throughout the whole target life (∼1000 kWh). [ABSTRACT FROM AUTHOR]