A research group led by Professor Masao Tanabe of Shibaura Institute of Technology and Toray Research Center, Inc. has succeeded in directly observing nanometer-scale (1 nanometer is 1 billionth of a meter) chemical structural changes occurring near the interface between Cu (copper) wiring and Low-k insulating film used in semiconductor wiring, using an analytical technique called AFM-IR.
Until now, in actual semiconductor wiring structures, conventional infrared spectroscopy has a wide measurement area and the signal is averaged with the surrounding area, making it difficult to directly evaluate chemical structural changes occurring in a very limited area near the Cu wiring. Therefore, the research group focused on atomic force microscopy-infrared spectroscopy (AFM-IR), which combines infrared spectroscopy (IR) and atomic force microscopy (AFM). AFM-IR is an analytical technique that enables chemical analysis on the nanometer order.
The research group used AFM-IR to investigate the chemical structure near the Cu wiring in a Cu/Low-k insulating film sample (an insulating material that suppresses electrical interference between wirings) that simulates a semiconductor wiring structure.
AFM-IR measurements performed on the surface of a Cu/Low-k insulating film wiring structure revealed that, compared to the central part of the Low-k insulating film, the Si-CH₃ (methyl group) and Si-H bonds, which are important for maintaining the performance of the Low-k insulating film, were reduced near the Cu wiring. Furthermore, components derived from hydroxyl groups (OH) were increased. Moreover, these chemical structure changes were concentrated in an extremely narrow region of about tens of nanometers from the interface.
This will enable detailed nanoscale analysis of the location and chemical changes that occur at the interface and in materials degradation during semiconductor manufacturing processes. It is expected to contribute to semiconductor material development, manufacturing process improvement, and the development of high-performance, high-reliability semiconductors.
Paper information: [Journal of Applied Physics] Interfacial structural modification in Cu/low-k interconnects revealed by atomic force microscopy infrared spectroscopy
