AVS 60th International Symposium and Exhibition
    Electronic Materials and Processing Thursday Sessions
       Session EM-ThA

Paper EM-ThA7
Analysis of Grain Structure and Electrical Resistivity of 17 nm Half-Pitch Copper Wires

Thursday, October 31, 2013, 4:00 pm, Room 102 A

Session: Materials and Process for Advanced Interconnects II
Presenter: J.S. Chawla, Intel Corporation
Authors: J.S. Chawla, Intel Corporation
K.J. Ganesh, Intel Corporation
B.J. Krist, Intel Corporation
J.S. Clarke, Intel Corporation
H.J. Yoo, Intel Corporation
Correspondent: Click to Email
We report electrical resistivity, copper grain size, and grain orientation distribution for 17-51 nm drawn wires fabricated with Cu/Ta, Cu/Ru and CuMn/Ru based processes on 300 mm Si wafer platform. Interconnects containing those structures measured in this study were fabricated using patterning and metallization schemes described earlier [1, 2]. The grain structure and size are characterized using a recently developed technique [3, 4], which couples diffraction-scanning transmission electron microscopy (D-STEM) configuration with precession electron diffraction (PED). Electrical resistivity and conducting cross section area of each wire is obtained by a four-point probe resistance measurement at various temperatures (25-75 οC) and lengths of wire (25-100 µm). The geometrical cross sectional area is measured using transmission electron microscopy (TEM), and shows the conducting cross sectional area for both Cu/Ru and Cu/Ta wires equals the geometrical Cu cross-sectional area. This result indicates neither Ru or Ta liner contribute to conduction, owing to their high resistivity compared to Cu at these dimensions.

The wires studied for this report have a conducting cross-sectional area ranging from 150 to 1100 nm2. The resistivity of Cu/Ru and Cu/Ta wires at conducting cross-sectional area of 200 nm2 is 4.6 and 7.7 µΩ-cm, respectively. The resistivity of the Cu/Ru wire is 40% lower than that of the Cu/Ta wire, and can be attributed to a larger (2x) median Cu grain area for the Cu/Ru, thus resulting in reduced electron scattering at grain boundaries. The resistivity delta between Cu/Ru and Cu/Ta wires decreases from 3.1 µΩ-cm to 0.8 µΩ-cm as area increases from 200 nm2 to 900 nm2. This is attributed to a combination of respective increase in grain size, and reduction in electron scattering at surfaces with increasing dimensions. The resistivity of a CuMn/Ru wire with 200 nm2 conducting cross-sectional area is 9.9 and 10.3 µΩ-cm with and without annealing, respectively. The higher resistivity for the CuMn/Ru wire is attributed to the Mn dopant, which increases impurity scattering. The electrical resistivity data is also consistent with the combined Fuchs-Sondheimer and Mayadas-Shatzkes expression.

References:

[1] M. van Veenhuizen et al., IEEE International Interconnect Technology Conference (IITC), 2012

[2] J. S. Chawla et al., IEEE International Interconnect Technology Conference (IITC), 2013

[3] K. J. Ganesh et al., Microscopy and Microanalysis, 16 (5), 2010

[4] K. J. Ganesh et al., Nanotechnology, 23 (13), 2012