Conference Paper

Full copper wiring in a sub-0.25 mu m CMOS ULSI technology

Semicond. Res. & Dev. Center, IBM Corp., Hopewell Junction, NY
DOI: 10.1109/IEDM.1997.650496 Conference: Electron Devices Meeting, 1997. IEDM '97. Technical Digest., International
Source: IEEE Xplore


We present the first fully integrated ULSI CMOS/copper
interconnect technology. Up to 6 Cu wiring levels are built at minimum
metal-contacted pitch of 0.63 μm, with W local-interconnect and
contact levels and a polycontacted pitch of 0.81 μm, on a
fully-scaled sub 0.25 μm, 1.8 V CMOS technology. The Cu wiring has
advantages of significantly lower resistance, higher allowed current
density, and increased scalability, relative to comparable Ti/Al(Cu)
wiring. These benefits in turn have enabled the scaling of pitch and
thickness, from reduced-capacitance, high-density lower levels to low RC
global wiring levels, consistent with high-performance and high-density
needs. The integrated Cu hardware was evaluated according to a
comprehensive set of yield, reliability, and stress tests. This included
fully functional, high-density 288 K SRAM chips which were packaged into
product modules and successfully tested for reliability. Overall, we
find the results for full Cu wiring meet or exceed the standards set by
our Al(Cu)/W-stud technology

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Available from: Andrew Simon, Jan 11, 2015
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    ABSTRACT: Electroplated copper films are known to change their microstructure due to the self-annealing effect. The self-annealing effect of electroplated copper films was investigated by measuring the time dependence of the film stress and sheet resistance for different layer thicknesses between 1.5 and 20 ??m. While the sheet resistance was found to decrease as time elapsed, a size-dependent change in film stress was observed. Films with the thickness of 5 ??m and below decrease in stress, while thicker films initially reveal an increase in film stress followed by a stress relaxation at a later stage. This behavior is explained by the superposition of grain growth and grain-size-dependent yielding.
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