An efficient approach to quantify the impact of Cu residue on ELK TDDB

Abstract

In this study, Triangular Voltage Sweep (TVS) is shown to be an effective way for quantifying the amounts of free Cu ions in porous low-k film. Free Cu ions at the interface that correlate with the Inter-Metal Dielectric (IMD) TDDB lifetime is also discussed. Adding a thermal treatment after the Chemical Mechanical Polish (CMP) process shows that the IMD TDDB lifetime can be improved by at least 2 orders of magnitude with a decrease in Cu ions at the interface. This study also proves that the TVS method can be used to evaluate Cu ions as well as Timeof-Flight Secondary Ion Mass Spectrometry (TOFSIMS).

Reliability limitations to the scaling of porous low-k dielectrics

“…We have shown previously that the effect of porosity on failure is accurately described by (1) and (2) [6,7,9]. LER impacts failure distributions at high voltage, distorting the failure distribution shape from Weibull as well as introducing systematic errors in the measured field dependence of failure [10].…”

“…Our experimental data is determined using hard breakdown as a failure criterion. Since the k value of these dielectrics is only controlled by the degree of porosity, we varied β to simulate failure distributions because β is a function of porosity as depicted by (2). We keep all other parameters in (1) constant and the LER magnitude was σ=4% of s. The β value is therefore determined to be β=6,4,and 3 for k=2.8,2.5, and 2.3 dielectrics.…”

“…Much effort has been expended to understand the processing influences and the physical mechanisms of low-k dielectric failure [1][2][3][4]. Clearly reliability considerations are important constraints on the reduction of k, but so far it has not been considered whether electrical breakdown will ultimately limit scalability, or if it will be constrained by factors such as mechanical stability or process damage [5][6][7][8].…”