| Copper (Cu) has been chosen to replace Al based alloys as the device interconnect material for advanced microelectronics. Cu has lower resistivity and higher electromigration resistance, and provides significant performance improvement, but Cu-based technology is a more complex technology. Hence, it is essential to understand the material properties of Cu interconnects, in particular their micro-crystalline structure. X-ray diffraction is a powerful technique widely used in materials research, and the advent of high brightness synchrotron radiation x-ray sources together with recent advances in x-ray optics have extended diffraction to spatially resolved measurements with sub-micron resolution.; The goal of this thesis is the local characterization of Cu interconnects using X-ray microdiffraction, lifetime tests and global stress measurements.; We performed extensive microstructure, stress and electromigration studies on our Cu samples. We observed that barrier layers have strong influence on the stress and microstructure development in Cu thin film. Electromigration tests were done on various samples, showing that barriers have also a significant impact on the reliability of Cu lines. Barriers seed different microstructures in Cu thin film, thus changing the atomic migration mechanism, and also affect the stress level of the Cu thin film, which is important in electromigration.; We have used the state-of-the-art X-ray micro-beam facility at the Advanced Photon Source (APS) to study the effect of the barrier materials on the crystal structure of Cu thin films. Various textures were found on Cu samples deposited on different barrier materials. Micro diffraction experiments were performed to map the strain distribution along patterned Cu lines with a ∼1 μ m resolution. Diffraction patterns from single grains were recorded on an x-ray CCD camera and techniques were developed to analyze the two dimensional micro-diffraction data to extract strain-stress relations. Strain measurements were done on the same line before and after electrical stressing. Strong strain variation was found after accelerated electromigration testing. These observations demonstrate the usefulness and potential of X-ray micro-characterization techniques in the electronic materials area. |
