Effects of Assembly Process Parameters on the Structure and Thermal Stability of Sn-Capped Cu Bump Bonds

Huffman, Alan; Lueck, Matthew; Bower, Christopher A.; Temple, Dorota

doi:10.1109/ectc.2007.374007

Cited by 26 publications

(11 citation statements)

References 5 publications

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“…As was demonstrated in previous work [3], the bonding yield of rigid bump structures is critically dependent on a number of factors, including the intrinsic flatness of the device, the degree of planarity with which the devices can be aligned to one another, and the bump height uniformity. The use of Cu/Sn bumps can provide compliance for the bonding process, allowing compensation for small height variations arising from these factors and resulting in a high bonding yield.…”

Section: Introductionmentioning

confidence: 93%

High density Cu-Cu interconnect bonding for 3-D integration

Lannon

Gregory

Lueck

et al. 2009

2009 59th Electronic Components and Technology Conference

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The demand for more complex and multifunctional microsystems with enhanced performance characteristics is driving the electronics industry toward the use of best-ofbreed materials and device technologies. Three-dimensional (3-D) integration enables building such high performance microsystems through bonding and interconnection of individually optimized device layers. Bonding of device layers can be achieved through polymer bonding or metalmetal interconnect bonding with a number of metal-metal systems (e.g. Cu-Cu, Cu/Sn-Cu, etc.) currently under development. RTI has been investigating and characterizing Cu-Cu and Cu/Sn-Cu interconnect processes for high density area array applications, demonstrating bonding between pads less than 15 microns in diameter for large area array configurations. Cu and Cu/Sn bump fabrication processes were developed that provide well-controlled surface topography necessary for the formation of low resistance, high yielding, and reliable interconnects.In this paper, the effects of Cu interconnect bonding parameters (pressure and temperature) and thermal reliability testing (thermal cycling and aging) on electrical connectivity and mechanical strength are presented and compared to Cu/Sn-Cu interconnect bonding with an eye toward small pitch scaling and ease of assembly. The conditions for producing Cu-Cu bond strengths > 110 MPa and electrical connectivity as high as 99.999% are described. IntroductionOf the bonding techniques available for creating 3D integrated devices, metal-metal bonding appears to be the most compatible with die-to-die and die-to-wafer configurations for facilitating processing of known-good-die (the preferred route for integrating chips from low-yielding IC processes) and integrating chips of heterogeneous materials [1,2]. Thermocompression bonding between arrays of Cu bumps (Cu-Cu bonding) and solid-liquid diffusion bonding between arrays of Cu and Cu/Sn bumps (Cu/Sn-Cu bonding) have been investigated for vertical integration of two or more devices because the rigid nature of these non-collapsible bump structures allows for very fine pitch interconnections to be made with low risk of bridging between neighboring interconnects.In addition, the metal-metal bonds are mechanically stable during subsequent thermal processes, which allows for the stacking of multiple layers of devices without disturbing the interconnections formed in previous bonding cycles.When bonding two chips in a face-to-face configuration (the simplest case of 3D integration), the choice of the bonding metallurgy is likely to be dictated by the device surface topography and the temperature limitations of the

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Section: Introductionmentioning

confidence: 93%

High density Cu-Cu interconnect bonding for 3-D integration

Lannon

Gregory

Lueck

et al. 2009

2009 59th Electronic Components and Technology Conference

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“…Recent investigations in the field of SLID technology are connected to the processing and assembly aspects [9,10,11], reliability [12,13], microstructure [5] and new metallurgies [14]. Since the application of SLID technology on miniaturized microbumps has shown a lot of issues (like gaps between bumps, voids, misalignment, squeeze of LMM etc.…”

Section: Introductionmentioning

confidence: 99%

Effects of bonding pressure on quality of SLID interconnects

Panchenko

Grafe

Mueller

et al. 2012

2012 4th Electronic System-Integration Technology Conference

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The investigation of the bonding pressure change on the different quality aspects of the solid-liquid interdiffusion (SLID) interconnects is presented. The stacks were produced by a flux-assisted bonding of two Si dies with an area array of square Cu/SnAg bumps on the bottom die and Cu bumps on the top die at approx. 250 °C. The bonding pressure was varied between 0 MPa, 0.35 MPa, 0.69 MPa, 1.04 MPa, 1.38 MPa, 1.73 MPa, 2.08 MPa, 2.42 MPa. Cross-sections of the stacks were analyzed by optical microscopy and scanning electron microscopy (SEM). Tilt, standoff height (SOH) variation, void fraction, interlayer thickness and Cu3Sn thickness were measured. It will be shown that increase of the bonding pressure can reduce the void fraction from 35.1 % (0 MPa) to 10.7 % (2.42 MPa) and decrease the interlayer thickness at the same time. Decrease of the interlayer thickness is accompanied by solder squeeze and increase of Cu3Sn thickness. Shear tests revealed an average shear str ength of (81.3 ± 21.5) MPa for the produced samples. The analysis of the fracture surfaces with SEM revealed that the weakest interface is located between Cu6Sn5 and Cu3Sn intermetallic compounds (IMCs) close to the initial Cu bump

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“…It was reported that the surface roughness of the Cu columns increased with the deposition time, due to the continuous growth of the Cu grains in both longitudinal and lateral directions. Currently, Cu pillars with an electroplated Sn layer, namely, Cu-Sn pillars, are widely used to form the vertical interconnections for practical applications (Huffman et al , 2007; Agarwal et al , 2010; Kwak et al , 2012).…”

Section: Introductionmentioning

confidence: 99%

Fabrication and characterization of Cu-Sn-Ni-Cu interconnection microstructure for electromigration studies in 3D integration

Xiao

Munief

et al. 2016

SSMT

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2016),"Thermo-mechanical challenges of reflowed lead-free solder joints in surface mount components: a review", Soldering & Surface Mount Technology, Vol. 28 Iss 2 pp. 41-62 http://dx.If you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services.Emerald is both COUNTER 4 and TRANSFER compliant. The organization is a partner of the Committee on Publication Ethics (COPE) and also works with Portico and the LOCKSS initiative for digital archive preservation. AbstractPurpose -The purpose of this paper is to fabricate a new Cu-Sn-Ni-Cu interconnection microstructure for electromigration studies in 3D integration. Design/methodology/approach -The Cu-Sn-Ni-Cu interconnection microstructure is fabricated by a three-mask photolithography process with different electroplating processes. This microstructure consists of pads and conductive lines as the bottom layer, Cu-Sn-Ni-Cu pillars with the diameter of 10-40 m as the middle layer and Cu conductive lines as the top layer. A lift-off process is adopted for the bottom layer. The Cu-Sn-Ni-Cu pillars are fabricated by photolithography with sequential electroplating processes. To fabricate the top layer, a sputtered Cu layer is introduced to prevent the middle-layer photoresist from being developed. With the final Cu electroplating processes, the Cu-Sn-Ni-Cu interconnection microstructure is successfully achieved. Findings -The surface morphology of Cu-Sn pillars consists of densely packed clusters which are formed by an ordered arrangement of tetragonal Sn grains. The diffusion of Cu atoms into the Sn phases is observed at the Cu/Sn interface. Furthermore, the obtained Cu-Sn-Ni-Cu pillars have a flat surface with an average roughness of 13.9 nm. In addition, the introduction of Ni layer between the Sn and the top Cu layers in the Cu-Sn-Ni-Cu pillars can mitigate the diffusion of Cu atoms into Sn phases. The process is verified by checking the electrical performance using four-point probe measurements. Originality/value -The method described in this paper which combined a three-mask photolithography process with sequential Cu, Sn, Ni and Cu electroplating processes provides a new way to fabricate the interconnection microstructure for future electromigration studies.

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Effects of Assembly Process Parameters on the Structure and Thermal Stability of Sn-Capped Cu Bump Bonds

Cited by 26 publications

References 5 publications

High density Cu-Cu interconnect bonding for 3-D integration

High density Cu-Cu interconnect bonding for 3-D integration

Effects of bonding pressure on quality of SLID interconnects

Fabrication and characterization of Cu-Sn-Ni-Cu interconnection microstructure for electromigration studies in 3D integration

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