Growth process of thin chemical vapor deposition-aluminum films and its underlayer dependence—real-time monitoring of reflected light intensity at the depositing surface

It is known that the reflectivity of aluminum (Al) film deposited by chemical vapor deposition (CVD) decreases with an increase of film thickness as its surface roughens. A thin, smooth film is effective for filling small holes and narrow trenches by confonmal deposition, but a rough surface is not effective. In this study, a real-time monitoring of the CVD-A1 film deposition process has been attempted by measuring the reflected light intensity at the depositing film surface. By finishing the deposition when the monitored reflected light intensity of the He-Ne laser reached the maximum, a film with a very smooth surface could be reproduced. Furthermore, the lower limitation of smooth continuous film thickness was compared for four different cases. Investigated underlayers were Ti and TiN deposited by sputtering (SPT). On these underlayers, CVD-Al film was deposited without exposure to atmosphere or with exposure to atmosphere prior to the deposition, resulting in a total of four deposition conditions. The results showed that Al film deposited on TiN without exposure to atmosphere had the thinnest and the smoothest continuous film among the four. Since the thickness was 60 nm, the filling of 0.12-μm diameter holes or 0.12-μm wide trenches can be expected by this process.