Comparison of the electromigration behaviors between micro-bumps and C4 solder bumps

Cai, Weihua; Yu, C. H.; Tung, Cheng-Huang; Huang, Renee; Hsieh, Chao-Ping; Chiu, Catherine; Hsiao, Hsiang Yao; Chang, Yuan; Lin, Chung‐Kuang; Liang, Yuhao; Chen, C.; Yeh, Ta‐Chuan; Lin, Larry; Yu, Douglas

doi:10.1109/ectc.2011.5898590

Cited by 15 publications

(8 citation statements)

References 13 publications

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“…Lu et al observed rapid depletion of IMCs and UBM consumption that led to significant damages caused by the fast diffusion of Cu and Ni along the c-axis of Sn crystals. Our previous study has shown a very different EM behavior of bumps when compared with the C4 bumps and confirmed the effect of Sn grain orientation on bumps [3].…”

Section: Introductionsupporting

confidence: 65%

“…When the scaling of semiconductor process technology becomes more challenging, 3D integration is becoming increasingly attractive as it promises benefits in system performance, small form factor, heterogeneous integration while at significantly reduced system integration cost and power consumption [1][2][3]. Solder bump is one of the key enabling technologies for 3D integration where high I/O count devices and interposers are interconnected with hundreds of thousands of bumps.…”

Section: Introductionmentioning

confidence: 99%

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Generic rules to achieve bump electromigration immortality for 3D IC integration

Chen

Shih

Cai

et al. 2013

2013 IEEE 63rd Electronic Components and Technology Conference

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An immortal solder micro-bump (bump) electromigration (EM) lifetime has been demonstrated for 3D IC integration. This ultimate goal was achieved under strictly controlled conditions, including the optimal design of bump metallurgy, geometry, optimized processes, along with welldefined stressing conditions and manufacturing window. The current carrying capability and EM lifetime of bump have been investigated as functions of stressing conditions which are correlated with the degradation mechanisms. When stressed under the appropriate g conditions, all bump test samples survived prolonged stressing, some over 13,000 hours, without a failure. Cross-sectional analyses revealed that the entire solder joint almost all transformed into intermetallic compounds (IMCs) with very minor or no voids. The resistance plots showed an initial fast rise in resistance due to IMC formation, then gradually leveled off and eventually reached a steady state. The observed degradation mechanism is dominated by IMC formation, which is the same as that of the user conditions. On the other hand, void formation that eventually led to open failure was the dominant degradation mechanism when samples were aggressively stressed. In other words, when all other conditions were the same, the stressing conditions make a huge difference in determining between an almost immortal EM lifetime vs. a short lifetime using the same high quality bumps. The boundary that separates the stressing conditions is roughly defined and will be discussed.In addition, since full IMC bump will become inevitable in the future miniaturized solder interconnect structure, the EM behavior of IMC dominated bump has also been evaluated in this study. Under highly accelerated stressing conditions of 174°C, at 1.6×10 5 A/cm 2 current density, the IMC dominated bumps were able to survive more than 600 hours and are still going strong. In comparison, solder bump failed quickly after just 107 hours when stressed under the same condition. This comparison study clearly demonstrated that IMC dominated joint has significantly higher current carrying capability than that of the solder joint. After reviewing all the data, we have concluded that the failure criteria for solder bump should be raised significantly higher than the 20% criteria traditionally used for the much larger C4 bumps.

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Section: Introductionsupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Generic rules to achieve bump electromigration immortality for 3D IC integration

Chen

Shih

Cai

et al. 2013

2013 IEEE 63rd Electronic Components and Technology Conference

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“…As illustrated in Figure 1, compared to the conventional Controlled Collapse Chip Connection (C4) bumps, the structures of fine-pitch microbumps are evolving significantly as the solder volume is largely reduced and the BLM-solder interaction becomes more important [2,3]. Since the total height of microbump is very small (< 20um), the IMC may dominate the mechanical and electrical properties of the entire bumps [4,5,6]. Furthermore, reflow process can accelerate the growth of IMC of Cu, Ni, Sn, etc., during the stacking of multiple chips, which has a profound impact to the chip stack assembly yield and reliability.…”

Section: Introductionmentioning

confidence: 98%

NiFe-based Ball-limiting-metallurgy (BLM) for microbumps at 50μm pitch in 3D chip stacks

Dang

Wright

Maria

et al. 2013

2013 IEEE 63rd Electronic Components and Technology Conference

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In this work, Pb-free microbumps at 50µm pitch with NiFe-based Ball-limiting-metallurgy (BLM) are fabricated and tested. Detailed microstructural analysis has been performed, which shows a uniform thin layer (~0.2µm) of FeSn 2 Intermetallic Compound (IMC) is formed between the Pb-free solder and NiFe BLM after the first reflow. In comparison, the NiCuSn IMC can grow more than 2µm in microbumps with the conventional Ni BLM or solder-caped Cu pillar after the first reflow. An excessive lateral "thermal-undercut" has been discovered in NiFe BLM structures during solder reflows due to good edge wettability of NiFe. A dual-layer BLM structure is proposed and demonstrated to mitigate the "thermalundercut". Moreover, addition of NiFe layer on a micro-Cu pillar structures have been demonstrated and characterized.

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“…26 However, for electromigration in microbumps with solder thickness less than 20 lm under high current densities, the resistance curve behaves completely different. [27][28][29][30] The resistance increases abruptly in the beginning, followed by more gradual increase, thus causing the resistance curve to behave concave-down. Wei et al conducted electromigration tests in microbumps by 9.6 Â 10 4 A/cm 2 at 168 C and they observed concave-down resistance curves.…”

Section: Introductionmentioning

confidence: 99%

“…Wei et al conducted electromigration tests in microbumps by 9.6 Â 10 4 A/cm 2 at 168 C and they observed concave-down resistance curves. 27 Lin et al stressed microbumps at 1.23 Â 10 5 A/cm 2 at an ambient temperature of 130 C and they detected concave-down resistance curves. 28 Similar results were also found in 5 lm-thick-solder microbumps with 30 lm pitch stressed at 10 4 -10 5 A/cm 2 at 150 C. 29 Chen et al also reported a fast initial rise in resistance, then gradually taper-off and reaches a steady state after prolonged stressing in microbumps stressed under 1.0 Â 10 5 A/cm 2 at 140 C. 30 However, there have been no studies addressing this interesting phenomenon and the discrepancy in results.…”

Section: Introductionmentioning

confidence: 99%

Experimental and simulation analysis of concave-down resistance curve during electromigration in solder joints

Lin

Chang

Chen

2014

Journal of Applied Physics

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Resistance curves play a crucial role in detecting damage of solder joints during electromigration. In general, resistance increases slowly in the beginning, and then rises abruptly in the very late stage; i.e., the resistance curve behaves concave-up. However, several recent studies have reported concave-down resistance curves in solder joints with no satisfactory explanation for the discrepancy. In this study, electromigration failure mode in Sn2.5Ag solder joints was experimentally investigated. The bump resistance curve exhibited concave-down behavior due to formation of intermetallic compounds (IMCs). In contrast, the curve was concave-up when void formation dominated the failure mechanism. Finite element simulation was carried out to simulate resistance curves due to formation of IMCs and voids, respectively. The simulation results indicate that the main reason causing the concave-down curve is rapid formation of resistive Cu 6 Sn 5 IMCs in the current-crowding region, which are 9 times larger than Cu IMCs. Therefore, when Cu reacted with Sn to form Cu 6 Sn 5 IMCs, resistance increased abruptly, resulting in the concave-down resistance curve. V

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Comparison of the electromigration behaviors between micro-bumps and C4 solder bumps

Cited by 15 publications

References 13 publications

Generic rules to achieve bump electromigration immortality for 3D IC integration

Generic rules to achieve bump electromigration immortality for 3D IC integration

NiFe-based Ball-limiting-metallurgy (BLM) for microbumps at 50μm pitch in 3D chip stacks

Experimental and simulation analysis of concave-down resistance curve during electromigration in solder joints

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Comparison of the electromigration behaviors between micro-bumps and C4 solder bumps

Cited by 15 publications

References 13 publications

Generic rules to achieve bump electromigration immortality for 3D IC integration

Generic rules to achieve bump electromigration immortality for 3D IC integration

NiFe-based Ball-limiting-metallurgy (BLM) for microbumps at 50&#x03BC;m pitch in 3D chip stacks

Experimental and simulation analysis of concave-down resistance curve during electromigration in solder joints

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NiFe-based Ball-limiting-metallurgy (BLM) for microbumps at 50μm pitch in 3D chip stacks