Abstract
One of the most outstanding problems in multilevel interconnect technology is the filling and planarization of metals in deep vias and trenches. Due to the shadowing effect, metal via filling with large aspect ratio using conventional deposition techniques is known to be very difficult. A directional deposition technique, known as partially ionized beam deposition (PIB) shows that oxide trenches with an aspect ratio of 3 can be filled wall to wall with Al or an Al–Cu alloy. Unlike conventional deposition techniques, Al films deposited by the PIB technique grow layer by layer and do not develop the usual overhang structure at the top corner of the vias. In this paper, a detailed study on the effects of impurities, either from a poor vacuum condition or from the substrate, on the PIB via/trench filling is presented. It is found that the surface mobility is greatly reduced as the vacuum pressure is increased from 10−4 Pa. It is also shown that the minimum substrate temperature (normally less than 200 °C) required for PIB via/trench filling is different for different types of oxide such as thermally grown, plasma enhanced chemical vapor deposition (PECVD), and tetraethylorthosilicate (TEOS) oxides.
Published Version
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