Liquid-crystal deflector

Abstract

Aluminum (Al) bumps are observed over contact holes when the chemical vapor deposition-physical vapor deposition (CVD-PVD) Al filling process is employed in sub micron technology. Boundaries of bumpy Al grains are formed inside the contact holes, while those of smooth Al grains are formed at the neck of the contact holes. Transmission electron microscopy (TEM) is employed to observe the crystallographic orientation of bumpy and smooth Al grains, and the results are 220 and 111 on {100} silicon surface, respectively. It is known that the growth rate of Al in the 220 direction is higher than that in the 111 direction because of its lower plane density. The difference in growth rate between the 220 direction and the 111 direction is believed to lead to bump formation. A modified PVD Al process to form grain boundaries at the neck of the holes is developed to prevent bumpy Al formation and fill the holes completely.