Reliability testing of Cu-Sn intermetallic micro-bump interconnections for 3D-device stacking

Abstract

In this work, two different reliability experiments, thermal cycling and electromigration, are performed on fully packaged Si-to-Si stacks bonded with Cu-Sn intermetallic (IMC) micro-bumps. These experiments investigate both the more critical thermo-mechanical behavior as well as the expected positive thermalelectrical behavior. The Cu-Sn IMC bumps survive thermal cycling for more than 3900 cycles between -40 and 125 o C with 1 hour per cycle. The resistance to electromigration is strongly dependant on the used Sn thickness and shows an improved performance for thinner Sn samples (3.5µm) compared to thicker Sn (8µm). In either case, IMC bumps outperform standard solder flip chip bumps.

High density interconnect bonding of heterogeneous materials using non-collapsible microbumps at 10 μm pitch

“…As expected from a C bond-to-bond alignment is consisten to edge. Some slight voids are seen what has been reported previously interconnects [2,3,7]. From the SEM ima approximately 2 μm in x is seen in the alignm across the array from left to right, compar expected from the CTE calculation.…”

Dynamical IMC-growth calculation

“…(5) and (6) are used. The heat of solution H S was also required for the calculation of the thermomigration in Eq.…”

“…This leads to the result that with a shrinking bump size the IMC layers become more and more important. Especially micro bumps with a diameter of less than 40 μm IMCs can be transformed to full IMC contacts [3][4][5]. Based on the knowledge of the IMC-growth the development of aging models for BGAs and concepts for the fabrication of IMC joints for IC stacks with μBGAs will be possible.…”

Numerical analysis of thermo-mechanical characteristics of solder joint depending on change in solder junction structure of MCP

“…In the existing junction structure of such solder joint, it is true that the ratio of solder's volume is reduced to decrease the size of an entire package and intermetallic compounds of joint [9] in case of die stacking, which results into a decline of reliability of solder joint. In particular, since a fine pitch size causes solder bridging, an existing junction structure has limitation in decreasing its package size.…”