Density Functional Theory Study of Cu Adhesion on Rh, Ir, Pd, Ta, Mo, Ru, Co, and Os Surfaces

Abstract

In this work, first-principles calculation based on the density functional theory was applied to study Cu adhesion on the surfaces of Rh(111), Ir(111), Pd(111), Ta(110), Mo(110), Co(0001), Os(0001), and Ru(0001), on which the adsorption energy, electron density difference, and geometrical structures of Cu were investigated. The analysis of the calculated and experimental results shows that the atomic chemical interaction, surface lattice mismatch, and crystal lattice type have marked effects on Cu adhesion on glue layers. Cu atoms on all the metal surfaces studied in this work are more likely to form the fcc structure with a quasi-(111) orientation. The coupling effect of the large surface lattice mismatch and the lattice type difference between Cu and the metal surface can greatly reduce Cu adhesion ability. Among all the studied metals, Ir and Os showed comparable adhesion ability to Ru and can be considered as promising Cu glue layers for Cu interconnects.

Ru passivated and Ru doped ε-TaN surfaces as a combined barrier and liner material for copper interconnects: a first principles study

“…The binding energies and valence charge of one Cu adatom at these sites are given in Table 3. Adsorption of Cu adatoms on Ru(0 0 1) surface has been studied earlier by Qu and co-workers 29,46 using DFT and ultrasoft pseudopotentials. However, they did not compute the hopping/association barriers or sub-surface diffusion barriers of the adatoms, which we have focused in this section.…”

“…There have been fewer theoretical studies using density functional theory (DFT) on the use of refractory metals as copper diffusion barriers or their use as liner layers, focusing on a variety of different metals. 28,29 Pure TaN is an excellent barrier for copper diffusion, however it is not well suited for copper electroplating. 7 Nevertheless, when combined with a suitable liner material such as Ru, it has great potential to overcome some of the challenges mentioned above.…”

Incorporation of tungsten or cobalt into TaN barrier layers controls morphology of deposited copper

“…This is usually not feasible and therefore it is reasonable to select the primary properties of interest and focus on modelling these. Adhesion is the property that is most easily studied using theoretical methods [32,[32][33][34]. Activation energy for atom diffusion can be determined using nudged elastic band calculations and can give insight into surface mobility of atoms as well as the diffusion barrier properties [35][36][37].…”

Study of direct Cu electrodeposition on ultra-thin Mo for copper interconnect

“…However, direct Cu electroplating process on diffusion barriers is very complex compared to that on Cu seed layer due to much higher resistivity of those barriers in comparison to Cu seed layer. Also Cu nucleation and growth on different barrier materials will be significantly different due to the different surface lattice structure of the barriers and different adhesion and interface properties between Cu and each kind of diffusion barriers [2]. Recently, Ru, Ir, and…”

“…Scharifker and Hills developed a mathematical model to describe the nucleation mechanisms with current-time transients[21]. The models for instantaneous and progressive nucleation are given by equations(2) and(3), respectively[21], i m and t m are the maximum current and the corresponding time, respectively.The curves plotted using Scharifker and Hill's model and our experimental results are shown inFig. 2(b).…”