Reliability of ultra-porous low-k materials for advanced interconnects

Abstract

Summary form only given. The reliability of new ultra-porous low-k materials is often a fascinating and complex tale involving multiple concepts from material science, electrical and chemical engineering. Pursuing an understanding of reliability for novel low-k materials requires the dissection of fundamental mechanisms and phenomena altering the electrical and physical properties of the dielectric matrix. Failure mechanisms can be categorized into two main groups. Intrinsic failure arises from damage to the dielectric matrix due to the transport of charge carriers. Ion catalyzed failure results from the drift of ionic species originating from the metal/dielectric interface. Integration of sub-20nm process technology nodes can be radically advanced by resolving how major failure mechanisms coexist and collaborate to generate dielectric failures. Here, we present a set of dynamic applied field experiments designed to identify changes in the conduction and reliability of dielectric films as result of bias and temperature stress (BTS). It is shown that ionic species originating from the metal/dielectric interface can behave as trapping centers for charge carriers under BTS. Trapping of electrons into ionic centers could increase the scattering of charge carriers which leads to the additional formation of intrinsic defects across the dielectric matrix, thus accelerating intrinsic failure. A mechanism is proposed to describe how leakage current decay at the onset of BTS is related to charge carrier confinement into intrinsic and ionic defects. The kinetics of charge trapping events were found to be consistent with a time-dependent reaction rate constant, k = k0 · (t + 1)β-1 where 0<;β<;1. This formulation leads to a classic, stretched exponential decay rate that we are looking to use to help predict dielectric reliability.