Comprehensive reliability evaluation of a 90 nm CMOS technology with Cu/PECVD low-k BEOL

Abstract

Integration and development of Cu Back-End of Line (BEOL) with PECVD low-k organosilicate glass (OSG, also called SiCOH, carbon-doped oxide, CDO, etc.) for 130 nm and 90 nm CMOS technologies has been reported by a number of institutions. Here we report on a Cu/SiCOH technology which has similarities, but also enhanced integration and reliability characteristics while preserving the R and C performance levels. These enhancements have led to excellent reliability results reported here, and are expected to increase the robustness to high-volume manufacturing and extendibility to next-generation smaller dimensions. The SiCOH and cap mechanical, chemical, and electrical strengths are increased, as well as associated interfacial adhesions. These combine with an optimized Cu metallization. As chip-package reliability is most at risk for low-k dielectrics, improvements have been brought into the BEOL level structure, the kerf design, and in some cases new packaging materials. When combined with the dielectric material and interface improvements, redundancy exists in the protection against potential chip-packaging failures. No failures occur in the full rounds of chip-package reliability stress testing done here on multiple wirebond and flip-chip packages. These packaging and other reliability results are presented, including BEOL-specific tests [electromigration (E-M), stress-migration (S-M), time-dependent dielectric breakdown (TDDB), thermal cycling (T/C)], environmental [temperature-humidity-bias (THB)], and functional stressing of product modules. The stress criteria and results exceeded JEDEC standards. All Cu/SiCOH tests passed at the same levels as our concurrent 90 nm Cu/SiOF technology.