Sputtered copper films with insoluble Mo for Cu metallization: A thermal annealing study

Abstract

The thermal annealing behavior of Cu films containing insoluble 2.0 at.% Mo magnetron co-sputtered on Si substrates is discussed in the present study. The Cu-Mo films were vacuum annealed at temperatures ranging from 200°C to 800°C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) observations have shown that Cu 4 Si was formed at 530°C, whereas pure Cu film exhibited Cu 4 Si growth at 400°C. Twins are observed in focused ion beam (FIB) images of as-deposited and 400°C annealed, pure Cu film, and these twins result from the intrinsically low stacking-fault energy. Twins appearing in pure Cu film may offer an extra diffusion channel during annealing for copper silicide formation. In Cu-Mo films, the shallow diffusion profiles for Cu into Si were observed through secondary ion mass spectroscopy (SIMS) analysis. Higher activation energy obtained through differential scanning calorimetry (DSC) analysis for the formation of copper silicide further confirms the beneficial effect of Mo on the thermal stability of Cu film.

Thermal stability of Cu(W) and Cu(Mo) films for advanced barrierless Cu metallization: Effects of annealing time

“…Our previous studies have indicated that the doping of insoluble substances in Cu films can inhibit recrystallization and grain growth, and thus the formation of copper silicide, during annealing. [7][8][9][10][11][12][13][14] We have further confirmed that annealing of Cu(W) 11 and Cu(Mo) 12 films for 1 h at 400°C yielded no copper silicide and had a low resistivity and high thermal stability. The aim of the current study is to investigate the thermal reliability of Cu(W) and Cu(Mo) films after annealing for long periods of time.…”

Copper-Silver Alloy for Advanced Barrierless Metallization

“…14 To keep a barrierless Cu alloy system's resistivity low, we need to add minute quantities of alloying elements or compounds to a Cu film. Our other studies 5,6,[13][14][15][16] also record our successful use of effective insoluble alloying elements or compounds, such as refractory and transition metals (W, Mo, Ru, etc.) and their nitrides, for Cu barrierless metallization.…”

“…When the device dimensions are reduced to a nanometer scale, the resistance of the entire device will increase, due to higher resistivity and a surface scattered with thin barriers. 2 A barrierless metallization method based on enhanced thermal stability in Cu alloys has been proposed [3][4][5][6][7][8][9][10][11][12][13][14][15][16] as an alternative solution. For example, Cu(RuN) doped on barrierless Si is reported to be stable at temperatures up to 680°C.…”

Thermal Stability Study of Cu(MoN x ) Seed Layer on Barrierless Si

“…The copper silicide in the Cu(MoN x ) film is not observed until annealed at 580°C. The maximum stable temperature without copper silicide formation is thus 560°C, which is higher than those of 400°C and $200°C for Cu(Mo) 5 and pure Cu, respectively. This suggests the better thermal stability of the Cu(MoN x ) alloy film.…”

“…[2][3][4][5][6][7][8][9][10][11][12][13] Some have investigated the alloying of an insoluble substance (e.g., W 4 ) into Cu, which forms distinctive microstructures with good thermal properties on barrierless Si; these structures have valuable applications in materials science. Chu and Lin 12 reported an annealing method for Cu(WN)/Si by forming a self-passivated layer in order to improve the thermal stability of Cu films.…”