Research Of The Thin Films Of Cu-base Metallization On AlN Ceramic Surface

Aluminum nitride ceramic is an ideal electronic packaging material due to a unique combination of properties including high theoretical thermal conductivity, thermal expansion coefficient which is close to the silicon, high electrical properties and mechanical properties, innocuity. In practical application of AIN, AIN ceramic surface must be metallized. Multi-layer film technology is conventional way for synthesizing thin-film metallization, but it may increase the interface thermal resistance. In this paper, thin films metallization on AIN substrates were obtained with ion beam and magnetron sputtering method. Influences of preparation process and flim composition which affected adhesive strength, residual stress and resistivity of the films were researched. Additionally, the distribution of thermal stress was analyzed by finite element analysis method.Copper film was deposited on the surface of AIN substrate by magnetron sputtering method. In this process, uniformity of film which was deposited by dual targets magnetron sputtering has much better properties, whereas the higher depositon rate will be got with single target magnetron sputtering method. Moreover, Cu film had much better qualities such as well crystallization and adhesive strength as the higher deposition temperature was used. The residual stress in Cu film was tensile stresses, which increased firstly and then decreased with the increasing of the deposition temperature, the stress reached the peak value when the deposition temperature was 200℃. The stress of surface metallization Cu film on AIN substrate can be reduced by implantation of transition interface on AIN substratesNi-Cu films were obtained by using ion-beam assisted deposition and electron beam evaporation deposition method. It was found that, as the proportion of components changed, the replacement or interstitial solid solution wound be formed. Ni-Cu films which are deposited by ion-beam assisted deposition had much better qualities than others, and the higher tempereture is used the better qualities it will get. As the Ni content increasing, the morphology of the film changed greatly that the crystal grain in the film graw up, and the film turned to be looser. At the same time, a lot of defects came out. The residual stresses in Ni-Cu film are tensile stresses, which increased following the increasing of deposition temperature. The resistance of Ni-Cu films increased at first then decreased with the increasing of Ni, and the stress reached the peak value when the content of Ni turns to 60at%.Thermal stress of surface film metallization on AlN substrate was analyzed by finite element analysis method. The thermal stresses of Cu film and Ni-Cu film are tensile stresses. The maximum thermal stress of the film mainly goes into effect at the center of the film, and the stress reaches the lowest value at the center of the matrix. The higher the deposition temperature is, the greater the thermal stress of the film will be. Following with the increasing of the film thickness, the maximum thermal stress will decrease and the minimum thermal stress tends to increase. With the pakaging materials applied in the devices, the higher operating temperature which the smaller the film thermal stress will be.