Microstructure characteristics and properties of copper films sputtered in EMI shielding layer

With the increase of system operating frequency and chip switching speed, electro-magnetic interference (EMI) shielding materials were wildly used in chip packaging technology. Packaging manufacturing process which bring cracks from the outer EMI shielding layer into the inner die has important influence on chip quality. In this paper, the influence on manufacturing parameters, such as film thickness and self-annealing time, on film strength were investigated. The microstructure characteristics and properties of copper films under different film thicknesses and self -annealing time were discussed. Microstructural characteristics were analyzed using field emission scanning electron microscopy (FESEM) and film properties were measured by nano-indentation instrument. Experimental results show that the 4um thickness of sputter copper film can achieve the lowest hardness performance and highest young's modulus of 108.3GPa. After 60 hours of self-annealing at room temperature, the grain was more stable than that of electroplated copper. The film thickness was proved to have significant influence on chips mechanical properties. Microstructure characteristics when stainless steel was sputtered on the top layer is discussed.