Electromigration performance of Al-Si-Cu filled vias with titanium glue layer

Electromigration performance of vias filled with high temperature (480 degr ees C) sputtered Al alloys on Ti glue layers was investigated in comparison with W-stud vias. Electromigration lifetime and failure mode are quite dif ferent according to via structures and kinds of Al alloys used. Electromigr ation lifetime of W-stud via chain and Al-Cu filled via chain depends on th e via to via distances, while that of Al-Si-Cu filled via chain does not de pend on the via to via distances. Failure mode observations revealed that v oids were formed only at a few locations in the test structure in Al-Si-Cu filled via chain while voids were formed at every via in W-stud via chains and Al-Cu filled via chains. It is supposed that Al moves through the Al-Si -Cu filled vias during electromigration test in spite of the existence of t he Ti glue layer at the via bottom. The Al transportation, however, was pro hibited at W-stud vias and Al-Cu filled vias. Glue Ti deposited at via bott om was converted to Al-Ti-Si alloy in Al-Si-Cu filled vias, while Al3Ti all oy was formed at AI-Cu filled via bottom. It is speculated that Al transpor tation occurs through via bottom Al-Ti-Si alloy layer during electromigrati on test in the case of Al-Si-Cu filled vias. (C) 1999 Elsevier Science Ltd. All rights reserved.