Via-Filling Capability of Copper Film by CVD

Abstract

The via-filling properties of chemically-vapor-deposition (CVD) Cu film filled in deep submicrometer vias (diam of 0.11, 0.15 and 0.18 μm) were investigated with respect to various deposition parameters. A superior void-free via-filling by Cu film can be achieved at low temperature, low pressure, and high concentration of precursor species in the gas phase. However, these favorable conditions for void-free via-filling of Cu film also lead to slightly degraded film properties, including higher resistivity, higher content of impurities, degraded adhesion to substrate, and lower deposition rate, as compared with those obtained under the optimal deposition condition. Thus, a trade-off is needed between void-free via-filling and a superior film property. The key to achieve a void-free via-filling is to have a high probability of a re-emission event for the Cu-containing species inside the vias. Using helium (He) as the carrier gas is preferable to using hydrogen because the hydrogen reduction reaction would enhance the deposition of Cu, resulting in a decreased probability of a re-emission event and thus degrading the capability of void-free via-filling. In this study, we have achieved void-free filling by CVD Cu film in deep submicrometer 0.11 μm diam vias with an aspect ratio of 9.1 at and below deposition temperatures of 160°C, using a precursor flow rate of 0.4 cm3/min and at a deposition pressure of 60 mTorr. © 2003 The Electrochemical Society. All rights reserved.