First Lateral Contact Probing of 55-μm Fine Pitch Micro-Bumps

Abstract

Probing micro-bumps for pre-bond testing is an essential process to check for a known good die. In recent technologies, micro-bumps such those used in 3-D-IC are too small and dense, which gives the probing a new challenge. Moreover, developers are concerned that the tip ends of the micro-bumps are mechanically damaged during the pre-bond testing, which is detrimental for the post-process IC assembly. Thus, many low damage probing solutions have been developed, but they still inevitably damage the tip end of the micro-bumps when the conventional probing method, vertical contact, is used. In this paper, for the first time, we demonstrate lateral contact probing on 55-mu m pitch micro-bumps without any damage to the tip ends. We successfully realized the testing with monolithically fabricated probes by nickel electroplating with a high aspect ratio photoresist mold. The measured fatigue life of the fabricated probes was at least100 000 cycles. Furthermore, the measured current carrying capacity was more than 180 mA. Proving our concept, the contact test results on the micro-bumps showed no damage to the tip end, and the contact resistance was below 1.13 Omega. Finally, the10 000 probes achieved a uniform 55-mu m pitch, which ensured the possibility in real testing.