Investigation of copper diffusion in SiOF, TEOS-oxide and TCA-oxide using bias thermal stress (BTS) tests

By increasing the integration density, the performance and the reliability of integrated circuits is determined by the materials of the metallization and the dielectric. Copper is well suited for future metallization systems, because of its low resistivity and high electromigration resistance. The implementation of low dielectric reduces parasitic capacitance. A significant increase of the performance can be achieved by using copper and low dielectric. However, for copper metallization a diffusion barrier is necessary. Fluorine doped silicon oxide (SiOF) is discussed as a possible inorganic low dielectric and has therefore to be tested for its barrier performance. BTS tests are known as a method to accelerate copper diffusion and degradation in dielectric materials. To compare the barrier quality, BTS tests were performed on TCA oxide, TEOS oxide and fluorine doped TEOS oxide.