Research On The Structure And Performance Of The Cu-W Thin Films Deposited By Dual-target Magnetron Co-sputtering

Cu-W thin film is uesd widely in the field of Microelectronics and Electronic Devices due to excellent electric thermal conductivity and low thermal expansion. It is rather difficult to obtain Cu-W solid solution due to the insolubility and poor wetting property between Cu and W. In this paper, Cu-W thin films of metastable solid solution were deposited by dual-target magnetron co-sputtering.Firstly, the relationship between at% W and PW/PCu have been obtained through experiments. The structures and micrographs of Cu-W thin films were analyzed by EDS, XRD, SEM and TEM. Results reveal that Cu-W thin films consist of metastable solid solution of Cu in W or W in Cu.The structures vary with W content increasing, which are fcc of W in Cu, (fcc+bcc) two-phase regions and bcc of Cu in W metastable solid solution. The grain size reduces with the content of solute atom increasing. The formation of Cu-W metastable solid solutions attribute to that the atom energy is enough high to overcome the mix-heat and the nano-particles and a great deal of defects interfuse within thin films. In addition, the structures of Cu-W thin films in different growth stages are studied. Results reveal that W is crystal and Cu is non-crystal in the early stage, which is conducive to overcome the mixed heat between Cu and W. In the subsequent growth process, due to sputtering particle bombardment role, Cu gradually crystallized and formed the metastable solid solution with W.Secondly, effects of the component on the adhesive strength of Cu-W thin films are studied. Results reveal that the adhesive strength of two-phase Cu-W thin films is best. The effects of the substrates surface treating technique on the adhesive strength of W-based Cu-W thin film are studied. It is found that the technique of ion beam assistant bombardment implanting W particles can remarkably improve the adhesive property of W-based Cu-W thin films. The critical load is doubled over than the sample only sputter-cleaned by ion beam. The mechanism of ion beam assistant bombardment implanting enhancing the adhesion of W-based Cu-W thin films is analyzed. With the help of mid-energy Ar+ ion beam, W atoms can carry on diffusion into the Fe-substrate surface layer, Fe atoms in the substrate surface layer and W atoms interlace with one another, microcosmic mechanical meshing and diffusing combination on atom-scale among the Fe and W atoms through the film-substrate interface can be formed. The wettability and thermal expansion properties of the W atoms diffusion zone contained plentiful W atoms are close to that of pure W or W-based Cu-W film.Finally, the electrical and thermal properties of Cu-W films are studied. In electrical properties, the lattice distortion is produced due to the addition of solute atoms, so the resistance of Cu-W films increase with the content of solute atom increasing. In thermal properties, the thermal conductivity of Cu-W films is far below the bulk materials, it is mainly due to the micro-cracks and scattering of the border and crystal in film; the thermal expansion of Cu-W films in line with the basic rules mixed, which are below the value of theory.