Interlevel Insulation Reliability Evaluation

A test vehicle has been developed to monitor the reliability of interlevel insulator layers. It is an all test site wafer and is processed through all the semiconductor personalization steps. It becomes a representative part of a job or lot from which reliability data can be accumulated and projected. This is accomplished by utilizing a ramp stressing technique. As failed sites are found, the exact position or crossover leakage region is identified by employing combinations of three separate procedures: laser isolation, voltage probing, and resistance measurements. A physical analysis is made consisting of an optical and scanning electron microscope (SEM) examination, surface polishing, nonencapsulation sectioning and electron probe analysis. In the work discussed, the predominant failure mode was attributed to micron-sized particulates. Photolithography and quartz fissuring problems were also encountered and resulted in failure. It is described how analysis results combined with responsive manufacturing actions eliminated sources of insulator failure and significantly accelerated the process learning.