In MOSFET structures, copper diffusion into the SiO2 field insulator can also induce mobile charges, resulting in transistor parameter shifts [1,2]. Figure 2897 shows SIMS profiles of failed and good MOS structures. The root cause of the device failure
is due to gate oxide breakdown, induced by Cu (copper) contamination.
Figure 2897. SIMS profiles of failed (a) and good (b) MOS structures. 
 A. Mesli, T. Heser, Phys. Rev. B 45(20) (1992) 11632.
 F. Braud, J. Torres, J. Palleau, J.L. Mermet, C. Marcadal, E. Richard, Proceedings 1996 13th VMIC (1996) 174.
 Kin Man Yu, https://www6.cityu.edu.hk.