Dispersion feature in arbitrary direction of surface acoustic wave applied to property characterization of ultra-large-scale integrated circuit interconnect films

Abstract

The ultrasonic surface acoustic wave (SAW) technique is becoming attractive for accurate and nondestructive property determination for thin low-k films employed in the modern ultra-large-scale integrated circuit (ULSI). In this paper, the dispersive characteristics of SAW propagating along arbitrary directions on the layered films deposited on Si(100) were studied in detail. The computation time was reduced greatly by appling coodinate transformation. The calculation of 9×9 Christoffel matrix was simplified to 6×6 matrix for one film layer structure, and from 15×15 matrix to 10×10 matrix for two-layered structure. This work will benefit the on-line test of low-k film properties during ULSI fabrication. Furthermore, the limitation on the propagating direction of SAW can be eliminated in the measurement.