Effect of dielectric materials on stress-induced damage modes in damascene Cu lines

Abstract

The stress of damascene Cu integrated with silicon dioxide (SiO2) and a low-k material was analyzed by x-ray diffraction, and that of the via-line structure was evaluated using finite element analysis. In both cases, the hydrostatic stress of the Cu line embedded in SiO2 was greater than that of the Cu line with low-k dielectric, whereas the opposite was true for the von Mises stress. In particular, the von Mises stress in the via embedded in the low-k dielectric was large. It was also shown that the yield strength of the via embedded in the low-k material is severely reduced compared with that of the via embedded in SiO2. Therefore, the deformation of the via, due to high von Mises stress and low yield strength, is expected to be the important failure mode in the interconnects made with low-k dielectrics which have higher coefficient of thermal expansion and lower elastic modulus.

Study of Fatigue Behavior of 300 nm Damascene Interconnect Using High Amplitude AC Tests*

“…So far this has turned out not to be the case. However, we argue that the present data are qualitatively consistent with previously reported calculations [6,7] and measurements [8,9] of stresses in damascene structures.…”

Triaxial stress distributions in Cu/low-k interconnect features

“…However, larger stress values ͑500-600 MPa͒ that appear biaxial ͑ 11 = 22 ͒ in narrow Cu lines within porous low-k dielectrics were reported by Wilson et al,4 suggesting that the Cu was highly constrained in the transverse direction despite the presence of a highly compliant dielectric material adjacent to the lines. While Cu out-ofplane stress ͑ 33 ͒ values were consistently tensile in low-k dielectric arrays, 3 those embedded in porous low-k dielectrics appeared to switch from compressive to tensile over the range of measured linewidths. 4 In an effort to resolve these discrepancies, the current study was undertaken to perform a more through examination of the impact of smaller linewidth on stress in Cu arrays at technologically relevant dimensions.…”

“…Paik et al 3 indicated that in narrow Cu lines with organosilicate glass ͑OSG͒ dielectric material, the transverse stresses ͑ 22 , 33 ͒ were similar and lower in magnitude than the corresponding longitudinal stress ͑ 11 ͒. However, larger stress values ͑500-600 MPa͒ that appear biaxial ͑ 11 = 22 ͒ in narrow Cu lines within porous low-k dielectrics were reported by Wilson et al,4 suggesting that the Cu was highly constrained in the transverse direction despite the presence of a highly compliant dielectric material adjacent to the lines.…”

“…Conal E. Murray, 1,a͒ Paul R. Besser, 2 E. Todd Ryan, 3 The distribution of triaxial stresses within single damascene Cu/organosilicate interconnect structures as a function of linewidth, ranging from 45 to 250 nm, was measured using x-ray diffraction. Least-squares minimization techniques were employed to determine the volume-averaged stress tensors of the Cu features.…”

Externally constrained plastic flow in miniaturized metallic structures: A continuum-based approach to thin films, lines, and joints

“…Applying the curvature method to passivated (encapsulated) line structures have also been reported [70,[241][242][243]. The X-ray diffraction [63,83,86,87,[244][245][246][247][248][249][250][251][252][253][254][255][256][257][258][259], Raman spectroscopy [260,261], and micromachine-based [262] techniques have also been developed and employed in measuring stresses in specially designed metal line structures.…”