Mechanical characterization of CMOS metal layers

This paper reports on the strain rate dependence of the mechanical properties of aluminum-based metallization layers. Evaporated Al, sputtered Al_99%Cu_1%, and multilayers of mum-thick Al_99%Cu_1% films separated by thinner TiN/Ti layers are characterized using the bulge test, the microcompression method and the microtensile technique. Elastic, ductile and fracture parameters are extracted for strain rates depsiv/dt between 10^-4 to 10¹ s^-1. The Young´s modulus E of sputtered layers, 59 GPa, is marginally lower than that of evaporated films, 63 GPa. Both fracture strain epsiv_max and strength sigma_max of sputtered Al, 5.5% and 79 MPa, respectively, show no significant variation with de/dt, changing to epsiv_max = 2.1 % and sigma_max = 200 MPa when such films are stacked with TiN/Ti layers. Regarding evaporated Al, the failure parameters depend strongly on the strain rate: emax decreases from 33.2 to 1.3% and sigma_max increases from 153 to 380 MPa within the entire range of tested depsiv/dt values.