Grain size monitor of Al pad is necessary to assure pad quality and electrical performance in IC manufacturing. Currently, the sample is prepared either without pretreatment or with 4.9% HF stain or ion milling before grain size measurement. In this paper, we demonstrate the pretreatment has a pronounced effect on the grain size measurement and the method with ion milling pretreatment shows more reliable results. The mechanism is further discussed.

Failures caused by threshold voltage (Vt) shifts in sub-100nm technology transistors have become very difficult to both analyze and determine the failure mechanism. The failure mechanisms for Vt shifts are typically non-visible for traditional physical analysis methods such as SEM inspection or traditional TEM analysis. This paper demonstrates how nano-probing was used to carefully and fully characterize the Vt shift failure to determine a specific electrical signature for a specific failure mechanism and then with junction stain Transmission Electronic Microscopy (TEM) verify the subtle doping defect affecting the Static Random Access Memory function in the 65nm generation node. Device failure due to a lack of Lightly Dope Drain (LDD) implant induced by an inconspicuous spacer defect was determined to be the root cause of the failure.

In reliability test some chips suffered functional failure. Through a series of failure analysis experiments, the root cause was determined to be a silicon dislocation across LDD (Lightly Doped Drain) area causing p-n junction leakage. However, those failed samples all passed both CP (Chip Probe) and FT (Final Test) monitor. Therefore, it is reasonable to suspect that DVS (dynamic voltage stress) may enhance minor dislocations already existing before CP and FT. To prove this hypothesis, an experiment was designed to find the relationship between DVS and the depth of dislocation in silicon substrate. In conclusion, DVS could enhance dislocation across LDD area, which may induce reliability failure. Moreover, reliability concerns on this finding will be discussed in this paper.

In this paper, a case of package level reliability test failure was studied. A model of “Slice Defect”, which was identified as the root cause by failure analysis, is introduced. Experiment results are presented to approve that such model is in fact correct and the corrective actions are effective.