Process and Reliability of Air-Gap Cu Interconnect Using 90-nm Node Technology

Electrical Breakdown in Advanced Interconnect Dielectrics

“…More detailed questions about the manufacturing feasibility of presently targeted process and integration approaches to ULK materials and their ultimate impact on reliability need to be addressed. Although this technology still has much to do in terms of defining what portions of the interconnect stack should have such gaps and defining the proper integration strategy for such interconnect architecture (especially with regards to mechanically stability), one interesting result found with present approaches is that the observed IMD-TDDB result for an air-gap does not appear to be a 'show-stopper' [412,413], at least at a larger critical dimension. There remains a fair bit of uncertainty regarding the suitability of ULK/ELK dielectrics with k < 2.3 for high-volume manufacturing, but further advances in process and integration optimization of ULK/ELK can be expected.…”

Process Technology for Copper Interconnects

“…Isolated pores are desirable to prevent water and other contaminants from diffusing into the dielectric step during wet clean steps prior to metallization and during CMP. Because of all the problems associated with porous low-k dielectrics, there is renewed interest in using air-gap technology [29][30][31][32]. Because of all the problems associated with porous low-k dielectrics, there is renewed interest in using air-gap technology [29][30][31][32].…”

Dielectric failure mechanisms in advanced Cu/low-k interconnect architecture

“…In order to keep pace with the gate scaling beyond the 90 nm technology node, second xerogel [15], which are basically porous silica-based dielectrics. Ultimately, to achieve the most idealistic interconnect system with the lowest intra-line capacitance is by introducing air gaps as the IMD dielectric [16,17].…”

“…The PDF of the lognormal distribution is described in equation 2. 16. Like normal distribution, the lognormal distribution is a two parameter model.…”

“…Therefore, the crack paths occur at the direction of maximum shear stress instead of along the interfaces. Subsequently, Cu extrusion occurred through the crack paths, driven by the electrostatic forces 16. SEM cross-section images at (a) AA' displaying dielectric crack paths from Cu top corners and (b) at BB' illustrating Cu extrusion through the crack paths.…”