The mechanical properties of porous low-dielectric-constant (low-k) thin films have been investigated for the stability evaluation of multilevel-interconnect structures using nanoindentation, microscratch, and four-point bending tests. Stress-strain curves of these films are proposed to predict their strengths and to explain their deformation behaviors. Real stress-strain behaviors are analyzed and confirmed by combining the experimental data obtained from nanoindentation and microscratch tests. Soft low-k films exhibit large plastic deformation, while hard and brittle films fracture early. The interfacial adhesion strengths and delamination behaviors between thin-film layers have been also studied using microscratch and four-point bending tests. The mechanical failure of interconnect structures depends on the inferiority of film strength or interfacial adhesion. (C) 2004 Elsevier B.V. All rights reserved.