Tomoko Aoki

Measurement of Copper Drift in Methylsilsesquiazane-Methylsilsesquioxane Dielectric Films

Measurement of Cu drifts in methylsilsesquiazane-methylsilsesquioxane dielectric films in the presence of an electric field was conducted using bias-temperature stress (BTS) and capacitor-voltage (CV) analysis as well as time dependent dielectric breakdown (TDDB) stress. The amount of Cu ions in the dielectric films can be estimated making use of the flatband voltage shift ΔVFB from the BTS. Comparing the flatband voltage measured by CV analysis with the leakage current integrated over time, it is found that the main content of the leakage current during BTS is ionic current that can be attributed to the drift of Cu and mobile ions. The Cu ions cause the leakage current during TDDB stress to increase. The drift rate of Cu in methylsilsesquioxane is lower than the reported values in polyarylene ether (PAE) and fluorinated polyimide (FPI), and larger than that in plasma enhanced chemical vapor deposition (PECVD)-SiON.

Porous Silicon Oxynitride Films Derived from Polysilazane as a Novel Low-Dielectric Constant Material

A novel spin on material derived from perhydropolysilazane that converts into ultra-low k inorganic films is described in this paper. The obtained films, cured at 400°C in N 2 atmosphere, exhibit dielectric constants as low as 1.6 which do not change after holding the wafers in a clean-room mbient for 2 months. Cross-sectional SEM images of the cured films show the aggregation of small granules with diameters ranging from 5 to 30 nm. The films can be obtained by conventional SOG process: spin-coating, baking and curing, without any additional process such as hydrophobic treatment. The average atomic compositions of the films are, Si/O/N/C = 40/55/5/0.5 (atomic %), by XPS analysis. These results indicate that the films have hydrogen silicon oxynitride structures. No evolution of H 2 O and NH 3 was detected by TDS analysis in the temperature range of RT to 800°C. Hydrophobic Si-H and Si-H 2 groups remaining in the film might prevent water absorption, resulting in the low dielectric constant. The remainder of Si-H and Si-H 2 constituents in the cured films is the result of selective oxidation reactions of perhydropolysilazane in the baking process with the use of a specific catalyst. The structures of the films are tailored by altering the amount of the catalyst. In this study, we also demonstrate the relationship between the effect of the catalyst and the film properties.