Wafer Level Electromigration Tests for Production Monitoring

Smaller geometrics are requiring metal lines to carry higher current densities. This increases their susceptibility to electromigration. This paper describes the SWEAT test (Standard Wafer-level Electromigration Acceleration Test) which was developed to monitor electromigration susceptibility at the wafer level. The test is extremely fast, allowing evaluation of a metal line in less than 15 seconds. It also uses a specially designed test structure to concentrate those stresses which lead to voiding. Most importantly, this test allows the user to derate data obtained to give equivalent lifetimes the same as those obtained in conventional testing.