Preparation And Characterization Of Cu-Ge And Cu-Ge-M Functional Films

Cu-Ge binary alloy system can be divided into two parts of the solid solution and the compound because the solid solubility of Ge in Cu is large(about 9%).Ge is expected to be used to improve the stability of the Cu film because of its larger atomic radius,dissolved in Cu can cause larger lattice distortion.It is also reported that the Cu-Ge compound film has high stability,strong antioxidant capacity,excellent optical performance and so on.Theoretically,it is feasible for these two types films to be used in the preparation of barrierless layer structure(directly used as Cu seed layer).But there is still no systematic studies on the comparison about the stability and resistivity between the two kinds thin films.Based on the Cu-Ge binary equilibrium phase diagram,the solid solution and the compound films in this paper were prepared on single crystal Si(100)substrates by magnetron sputtering within a wide range of components.Firstly,the change of thin films' stability and resistivity were studied after vacuum annealing,and further to optimize the composition of solid solution Cu(Ge)films.Then the comparison of two kinds of thin films from several aspects,such as resistivity,hardness and stability were carried out.The results about the Cu(Ge)solid solution films indicate that the addition of Ge alone would lead to serious interfacial diffusion and promote the Cu-Si reaction due to the low diffusion activation energy and high diffusion coefficient of Ge in Cu.In order to improve this phenomenon,here,Fe(or Sn)were selected as the third element to prepare Cu(Ge-Fe(or Sn))ternary films.The strong interactions from the negative mixing enthalpy between Ge-Fe(or Sn)firmly stabilizes Ge in the Cu lattice and improves the thermal stability of the film.After 400 oC/1 h annealing,the Cu99.19Ge0.73Fe0.08 and Cu99.22Ge0.69Fe0.09 films with the largest lattice distortion still remained stable with the resistivity as low as 2.54~2.80 ??·cm.For Cu(Ge-Sn)films,the Cu-Si reaction did not occur in the Cu99.01Ge0.90Sn0.09 films which had the largest lattice distortion,and the resistivity was maintained at 2.51 ??·cm.The results proved that the strong interaction elements Fe and Sn could prevent the diffusion of Ge and enhance the stability of Cu alloy films.The addition of small atomic radius element Fe,which has large diffusion activation energy and small diffusion coefficient in Cu,could inhibit diffusion for a wide range of composition.The results of the research on Cu-Ge binary compound state films showd that the transformation from ? to ? and ?1 was in a highly coherent manner.Compared with the solid solution films,the compound films has no obvious advantage on performance: the hardness increased slightly.After annealing at 400 oC for 1 h,there was Cu3 Si particles in the samples in ?-Cu(Ge)and ?-Cu5 Ge phase zones.Though there was no producton of Cu-Si reaction in ?1-Cu3 Ge,the resistivity value was very high because that the grain didn't growth after annealing and the concentration of adding elements is high.As a result,it is feasible for the solid solution state Cu(Ge-Fe(Sn))films with nothing but composition optimization to be applied in Cu seed layer as the barrierless layer structure and the resistivity and stability can satisfy the subsequent processing of the microelectronics industry requirements.