Evaluation Method for Metal Line Failure Induced by High Current Density in Order to Ensure ULSI Reliability

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1.The parameter governing electromigration damage in the passivated bamboo line was newly formulated by adding the effect of stress on atomic diffusion to the governing parameter which has already been developed for unpassivated line. Using the parameter the simple and accurate method for derivation of film characteristic constants was developed.2.Acceleration ration tests of electromigration damage were performed where high-density electric current was supplied to the passivated aluminum bamboo line of submicron width for a certain period of time. Inputting the obtained velocity into the derivation method utilizing the governing parameter described in item 1 the film characteristic constants were obtained and the constants were concluded to be valid. From this fact, the governing parameter for electromigration damage newly developed was verified.3.It is known that there is a threshold current density of the electromigration damage in the via-connected line. Utilizing the governing parameter for electromigration damage a numerical simulation of the building-up process of the atomic density distribution was developed and thus we achieved the construction of the evaluation method of the threshold current density. This method is applicable to not only straight shape line but also the two-dimensionally shaped line such as angled line.4.Concerning the straight lines, the evaluation result that the threshold was in inverse proportion to the line length was obtained, and regarding an angled line the evaluation result that threshold of the angled line was greater than that of straight line was obtained. From experimental results the same tendency was obtained as the evaluation results, and thus the evaluation method was verified. It was found out that two-dimensional shape of the line affected threshold current density, and valuable knowledge for ensuring ULSI reliability was obtained.