Characterization and optimization of porogen-based PECVD deposited extreme low-k materials as a function of UV-cure time

Study of porogen removal by atomic hydrogen generated by hot wire chemical vapor deposition for the fabrication of advanced low-k thin films

“…The single most interesting feature of the broad absorption band in the region of 980-1250 cm −1 , is that the highest Si\O peak retained its maximum at approximately the same wave number, independent of the filament temperature. This is a strong indication that there was little transition from cage and suboxide types of Si\O bonds to network bonds, different from when the as deposited films were treated by a UV cure, as reported in [9]. The FTIR spectra in the 3000-3500 cm −1 region indicate that there is some water incorporation in the films when they were treated at temperatures higher than 1800°C.…”

“…Our approach for the process development included optimization of filament temperature to remove the porogen while targeting an ultra low-k value. Porogen removal has been generally analyzed with FTIR by observing the peak area of the C\CH x bending bonds (2800-3000 cm −1 ) [9]. Fig.…”

“…Fig. 1 shows FTIR spectra of the remaining C\CH 3 and C\CH 2 groups in the 2800 cm −1 to 3000 cm −1 range [9] as a function of filament temperature, for a H 2 treatment for 15 min. In the 1500°C to 1800°C range, at higher temperatures more porogens have been removed.…”

“…The film thickness was around 100 nm with within wafer non-uniformity of less than 10%. The film deposition conditions were detailed elsewhere [9,10]. The second process step was the removal of porogen.…”

“…The subtractive method requires at least two process steps: 1) co-deposition of a SiOC:H precursor and a sacrificial porogen (CH x ) precursor [5], and 2) removal of porogen. This removal can be done by several techniques, of which a remote plasma treatment [6,7] and a ultraviolet (UV) cure [8,9] are the most common. The UV cure treatment also may raise skeleton cross linking and enhance film mechanical properties [7] and may be, therefore, used as a third step in the subtractive method, when the second process step is a remote plasma [7,10].…”