Study of the effect on die backside stress from coating of a nitride layer

Place a Die breaking strength is related to the surface morphology of the die. Existing of the defects on the die backside makes die fracture becomes a more severe problem in the microelectronic package. In this study, impact of the die backside defects on the stress is investigated by mechanical theories. Finite element method and 3 point bending test are used to verify the theory prediction. Thin layers of AlN were coated on the backside of the dice with different morphologies. Mechanical properties of these dice were tested by 3PB method. It is found that coating a thin layer of AlN on the die backside can increase the die breaking strength. Furthermore, the stress at the crack tip and its vicinity, with and without coating layer, has been compared by using finite element simulation. The results suggested that coating a thin layer of AlN on the die backside is a feasible way to improve the mechanical property of the package and protect the package from fracturing.