Microstructure Study Of Sputtered Thin Layers In HDI Substrate

With the miniaturization and integration of ICs, the packaging and interconnecting technology is becoming a key to continue and transcend the "Moore’s Law". High density substrate has not only become the main form of packaging, but also one of the supporting technologies for "3D" package from now.Although HDI substrates have different layers and patterns, but they feature sputtered Ti/Cu thin layers as a "seed layer" in their advanced structures. The layers have submicron and even nanometer thickness, and their microstructures are more minimal. In this paper, a comparative study is carried on to the four means of characterizing the submicron microstructure from sample preparation, theory and practice.To protect the environment, lead-free soldering process has become the mainstream in the electronic package, with a higher operating temperature which will affect more on the sputtered microstructure than the traditional technology, thus harming the reliability of the final package. Here, XRD.. four-probe、AFM and so on are used to study how lead-free effect the microstructure and conductivity of the sputtered layers. Then, the microstructure and interfacial properties of sputtered Ti are researched by XRD and TEM, and the Ti layer is almost amorphous. A novel electrochemical method is designed to prepare fresh Ti layer for XRD, on which basis the effect of lead-free reflow on sputtered Ti nano-layer. This paper also found that sputtered Ti layer will crystallize after sputtering a ultra-thin Cu layer.In practice, HDI substrates often fail for the structure defect in the sputtered layers. Dual-beam FIB and an independent SEM are used to study the interface in the sputtered layer. A clever method was used to transform the sample from FIB to SEM. And further the results were revealed.