Low Dielectric Constant SiCOH Films as Potential Candidates for BEOL Dielectrics

The quest to improve the high performance in ULSI circuits, is driving the search for new materials with low dielectric constants (k=2.5-3.0) for the back end of the line (BEOL) interconnect structures. Novel SiCOH films comprising Si, C, O and H, have been deposited by a PECVD deposition technique. The films have been characterized as-deposited and after anneals of up to 8 hours at 400°C. The atomic composition of the films has been determined by RBS and FRES analysis and their optical properties have been determined by FTIR and index of refraction measurements. The mechanical properties have been determined by measurements of stress and of crack development velocity in water. Metal insulator silicon structures have been used to test the electrical properties of the SiCOH films. After an initial stabilization anneal, the SiCOH films are thermally stable up to 400°C, have low tensile stresses (<50 MPa), an extremely low crack propagation velocity, and a hydrophobic behavior. According to the deposition conditions the films have dielectric constants in the range of 2.8 to 3.5. These film properties, combined with an easy-to-integrate deposition process indicate that the material has a strong potential as an interconnect dielectric.