Impact of dielectric stack and interface adhesion on mechanical properties of porous ultra low-k

Introduced for next interconnect generations to replace dense low-k materials, porous dielectrics exhibit poor mechanical properties, which are difficult to evaluate with nanoindentation. Indeed, integrated ultra low-k material thickness which drastically influences mechanical properties is three times thinner than the one required for nanoindentation measurement. Therefore multilayers are used to obtain both the required thickness and the mechanical properties equivalent to integrated films. However, the hardness and Young's modulus determination become sensitive to interface adhesion and crack occurrence. As a solution, plasma treatments performed prior layer deposition increase the stiffness determined by nanoindentation by a factor of 3, thus evidencing that the integration of porous materials in multilayers is sensitive to mechanical properties and also to interface affinity.