Adhesive strength of electroplated copper films

A study has been conducted to characterise the scratch resistance and adhes ive strength of copper films electroplated on to thin layers of W/TiN/Si(10 0) and Cu/Ta/Si(100) substrates. The properties were characterised with a m icroscratch tester using diamond indenter of different sizes. For the elect roplated copper film on W seed, a 200 mum tip with an increased loading pro duced initially a minor delamination corresponding to damage along the side s 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 und erlying 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 mum tip. When a 50 gm indenter was us ed a minor delamination was seen initially at a force of 4 N, and this dela mination subsequently increased with increasing load, but no full delaminat ion 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 perfor med using a 20 mum diamond tip. The failure phenomenon for the film on Cu s eed is different from that on W seed. The initial failure was caused by rad ial cracking in the film, which turned into chipping of the film as the loa ding force increased. The film then completely delaminated, causing substan tial debris to be strewn along the scratch path. (C) 2001 Elsevier Science B.V. All rights reserved.