In this paper a quick wafer-level evaluation technique for elecaomigration immunity is proposed. Noise measurements (IK, W) m performed on a test pattern with smss gradients under high current density up to 2 x 1 0 7 A / d . Each of the measurements is completed within a few minutes. The temperature of interconnections ( 2 W C for current density of 2xlO7A/cn?) is low enough to evaluate elecmmigration. Effectiveness of our technique has been verified by observing the fact that cumnt noise spectrum is closely related to the void formation.
I "High speed charging/discharging of long signal lines with heavy capacitance is the m a t important feature of high performance VLSI devices. Realization of such devices quires highly reliable interconnection. Shrinkage in size of VLSI circuits q u i r e s the de-CICBSC in cross section of thin film interconnection. This leads to an increase in m n t density. Therefue, failure of interconnection due to elecuomigration becanes a crucial problem.To establish a fabrication process for advanced devices in a short period, we must develop a quick evaluation technique for electromigration: In the past, many studies on Electromigration have been made.. Conventional methods of evaluating electromigration take a few weeks to complete the test In order to d u c e the time for evaluating electranigration immunity, J.Meiggs ct.al. (1) perf& elecmmiption tests with higher current dtnsity. But some of the failures in i n t e r c o~d m s might have been caused by other factors such as transformation of passivation layer due to high temperature. B.J.Root et.al. (*) proposed the SWEAT (Standard Waferlevel Elecmmiption Accelerating Test) test with a panem that has both wide and narrow regions (fuse). It quires a few steonds to complete the test. But we observed that timc to failure (l'TF) in SWEAT testing depends on not only material parameters but other factors such as the width of intemnnection. Some test results did not coincide with the results of conventional mthods. On the other hand, T.M.Chen et.al. (3).(4) p r o p o d a sensitive evaluation method of elecmmigration by current noise measurements. Noise mtasuremnt revealed electrondgration damage after conventional elecmmigration tests. But the detail of the relation between void famation mchanism and noise measurement is not soIn our study, current noise measurements have been perf m d on the test pattern which is used for SWEAT testing. By comparing the results of noise measurement and the observation of passivated interconnection by high resolution optical microscope, it is verified that the c m n t noise specmum is closely related to the void formation. We also compared the results of elecmmigration testing by noise measurement to those of the conventional mcthcds for intemnnections which have different vertical swctuxes. They show a good correspondence.Consequently the present current noie measurement technique has proved to be a sensitive and effective wafer-level evaluation method for elecaomigration immunity. clearly understood -Al...
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