Lower-k SiCOH integration for 65 nm ground rules

Abstract

PECVD SiCOH integration, which has been in production from the 90 nm node with our SiCOH film having k=3.0 has two ways to go to extend to lower capacitance. One is to add porosity to become ultra low-k (ULK). The other is to stay with low-k SiCOH, which is modified to have a "lower-k". The effective k-value attained with the lower-k (k=2.8) SiCOH processed in the "Direct CMP" scheme is very close to that with an ULK (k=2.5) SiCOH film built with the "Hard Mask Retention" scheme. This paper first describes consideration of these two damascene schemes, whose comparison leads to the conclusion that the lower-k SiCOH integration can have more advantages in terms of process simplicity and extendibility of our 90 nm scheme under certain assumptions. These assumptions are that (i) Direct CMP is applicable to lower-k SiCOH, but risky to ULK, (ii) lower-k SiCOH can be intact against plasma damage, whereas ULK is too susceptible, (iii) no current modern CMP technologies can have across-the wafer-uniformity high enough to enable the "Hard Mask Retention" scheme in 300mm wafers, and (iv) unit processes established for the 90 nm k=3.0 SiCOH can be tweaked for the lower-k SiCOH without changing tool sets and materials/gases. Along these lines, this paper describes PECVD optimization for the lower-k SiCOH film, followed by our successful integration of the film in 65 nm ground rules. Data proves that the robustness of this lower-k SiCOH film can lead to a successful integration.Grant: Acknowledgements: This work is supported by the independent alliance programs for SOI and Bulk CMOS technology development.