Adhesive strength of electroplated copper films

A study has been conducted to characterise the scratch resistance and adhesive strength of copper films electroplated on to thin layers of W/TiN/Si(1 0 0) and Cu/Ta/Si(1 0 0) substrates. The properties were characterised with a microscratch tester using diamond indenter of different sizes. For the electroplated copper film on W seed, a 200 μm tip with an increased loading produced initially a minor delamination corresponding to damage along the sides of the scratch path followed by cracking at the centre of the scratch. A complete delamination of the film, causing tearing of the film from the underlying substrate, occurred at a critical load of 16 N. In the case of the film on Cu seed, no delamination was observed within the loading range up to 22 N under a 200 μm tip. When a 50 μm indenter was used a minor delamination was seen initially at a force of 4 N, and this delamination subsequently increased with increasing load, but no full delamination was found within the loading range of up to 22 N. The full delamination of the film on Cu seed occurred at 3 N when the scratch testing was performed using a 20 μm diamond tip. The failure phenomenon for the film on Cu seed is different from that on W seed. The initial failure was caused by radial cracking in the film, which turned into chipping of the film as the loading force increased. The film then completely delaminated, causing substantial debris to be strewn along the scratch path.