Metallization Qualification for VLSI (TRACE Test).

Abstract : The objective of this work was to define a standard test procedure to qualify VLSI metallization systems for government applications. The susceptibility of the metallization to electromigration was the primary concern of this qualification. Life tests were conducted in which a large number of test lines were stressed to failure. Resistance change was monitored and the correlation between rate of change and lifetime evaluated. It was determined that the correlation was small and therefore resistometric test methods are not suitable for predicting life. Finite element modeling of the resistance change process was used to explain some of the anomalous resistance variations which were observed. The time to failure was found to be log-normally distributed down to the 0.2% failure point. It was also found that a very long test line is statistically equivalent to many shorter lines when evaluating early failures. Therefore, a lift test in which a modest number of very long lines are tested to failure is an efficient test for evaluating early failures. Keywords include: Metallization; Electromigration; Quality control; Reliability; and Test pattern.