Failure Modes of Copper Interconnect in ICs
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The main failure modes associated with the integration of copper interconnect are:
         a) Metallization level failure
             a.i) Copper corrosion
             a.ii) Contamination
             a.iii) Interface diffusion
             a.iv) Electromigration
             a.v) Stress migration
             a.vi) Self heating
             a.vii) Joule heating
             a.viii) Stress voiding
             a.ix) Copper extrusion
             a.x) Via voiding
             a.xi) Interface adhesion
         b) ILD (inter-level dielectric) failure
             b.i) Cracks
             b.ii) Interface adhesion
             b.iii) Delamination
             b.iv) Moisture adsorption
             b.v) Intra-level and inter-level leakage
             b.vi) Bias-temperature instability
             b.vii) Mechanical weakness
             b.viii) Low thermal conductivity
             b.ix) Breakdown of low k dielectrics
         c) Failure of gate level and silicon active area
             c.i) Breakdown of the gate dielectrics
             c.ii) Soft breakdown (SBD)
             c.iii) Stress induced leakage current (SILC)
             c.iv) Direct tunneling
             c.v) Hot carrier injection (HCI)
             c.vi) Trap assisted tunneling (TAP)
             c.vii) Negative bias temperature instability (NBTI)
             c.viii) Interface instability
             c.ix) Migration
                    Copper migrating into silicon active areas can form deep level traps, causing a dramatic decrease of minority carrier lifetime or can form copper silicide precipitates resulting in leakage current at source and drain shallow junctions. Copper diffusion into the SiO2 field insulator can also induce mobile charges, resulting in transistor parameter shifts [1,2].
           d) Integration issues
             d.i) Thermal-mechanical issues
             d.ii) Interface adhesion
             d.iii) CTE (Coefficient of Thermal Expansion) mismatch
             d.iv) Chemical reaction
             d.v) Joule heating effects

 

 

 

 

 

 

 

 

[1] A. Mesli, T. Heser, Phys. Rev. B 45(20) (1992) 11632.
[2] F. Braud, J. Torres, J. Palleau, J.L. Mermet, C. Marcadal, E. Richard, Proceedings 1996 13th VMIC (1996) 174.

 

 

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