Introduction of an Electroless-Plated Ni Diffusion Barrier in Cu/Sn/Cu Bonding Structures for 3D Integration

Lee, Byunghoon; Jeon, Haseok; Kim, Soon-Jae; Kwon, Kee-Won; Kim, Jong‐Woong; Lee, Hoo-jeong

doi:10.1149/2.007202jes

Cited by 15 publications

(11 citation statements)

References 13 publications

(21 reference statements)

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“…The higher Cu concentrations and lower Sn concentrations observed below the electroless Ni-P plating layer as compared with those of the surroundings indicate the formation of Cu-Sn-based intermetallic compounds. Our FE-EPMA observations of the bonding interface of the p-type thermoelectric modules are consistent with previous studies, which concluded that Cu-Sn-based intermetallic compounds exist in the form of Cu 3 Sn and Cu 6 Sn 5 [23][24][25][26], and that they prevent interdiffusion between the Ni-P plating layer and Sn.…”

Section: Resultssupporting

confidence: 92%

“…The surface of the thermoelectric elements became rougher with increasing particle size of the alumina powder. As there was no chemical bonding at the interface between the thermoelectric element and the Ni-P plating layer, the adhesion of the electroless Ni-P plating layer could be secured via the physical surface roughness effect (i.e., the anchor effect) [23]. After sand blasting, the surfaces of thermoelectric element blocks subjected to electroless Ni plating were observed using a laser scanning confocal microscope ( Figure 2).…”

Section: Resultsmentioning

confidence: 99%

“…In this study, to improve the adhesion between the thermoelectric element and the plating layer, we introduced a rough interface via mechanical treatment such as sand blasting to utilize the anchoring effect [23]. The surface roughness of the Bi-Te-based thermoelectric element was controlled via the sand-blasting method using alumina powder.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Surface Roughness and Electroless Ni–P Plating on the Bonding Strength of Bi–Te-based Thermoelectric Modules

Bae

Kim

et al. 2019

Coatings

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In this study, electroless-plating of a nickel-phosphor (Ni–P) thin film on surface-controlled thermoelectric elements was developed to significantly increase the bonding strength between Bi–Te materials and copper (Cu) electrodes in thermoelectric modules. Without electroless Ni–P plating, the effect of surface roughness on the bonding strength was negligible. Brittle SnTe intermetallic compounds were formed at the bonding interface of the thermoelectric elements and defects such as pores were generated at the bonding interface owing to poor wettability with the solder. However, defects were not present at the bonding interface of the specimen subjected to electroless Ni–P plating, and the electroless Ni–P plating layer acted as a diffusion barrier toward Sn and Te. The bonding strength was higher when the specimen was subjected to Ni–P plating compared with that without Ni–P plating, and it improved with increasing surface roughness. As electroless Ni–P plating improved the wettability with molten solder, the increase in bonding strength was attributed to the formation of a thicker solder reaction layer below the bonding interface owing to an increase in the bonding interface with the solder at higher surface roughness.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Surface Roughness and Electroless Ni–P Plating on the Bonding Strength of Bi–Te-based Thermoelectric Modules

Bae

Kim

et al. 2019

Coatings

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“…Because diffusivity data do not exist for Cu in the Ni(P) film, it is difficult to assess the validity of this proposition. However, the possibility is not considered high here, because the Ni(P) film is known to be a good diffusion barrier to Cu [22][23][24] and the current ENIG process temperature 358 K (85°C) was significantly lower than those used in other studies. [24] If the Cu diffusion to the Ni(P) film surface was primarily responsible for the black pad occurrence, the preannealing of the Cu UBM at 423 K (150°C) before the ENIG treatment should induce significantly more black pad formation, which contrast with the beneficial role of the pre-annealing reported in Reference 12.…”

Section: B Effects Of Ag Au Ni and Co Ubmsmentioning

confidence: 98%

Effects of Under Bump Metallurgy (UBM) Materials on the Corrosion of Electroless Nickel Films

Kim²

2015

Metall Mater Trans A

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The ''black pad'' phenomenon, which refers to the blackening of electroless-plated nickelphosphorus [Ni(P)] films during the immersion Au process, is reproduced using pure chemicals and its fundamental mechanisms are investigated. In the present analysis, under bump metallurgy (UBM) materials have profound effects on the black pad susceptibility, and the presence of abnormally large nodules (ALNs) is essential to the black pad occurrence. The Ni(P) films over Cu, Ag, and Au substrates all exhibit ALNs and are susceptible to black pads, while those over Ni and Co substrates do not have ALNs and therefore are not susceptible to black pad. In the former cases, submicron scale nodular variations of the surface curvature lead to variations in the P concentration in the Ni(P) films, which induces sufficiently large potential differences to drive galvanic corrosion when exposed to the electrolyte, which is a gold cyanide solution in this study. The UBM effect is ascribed to differences in the Ni(P) film growth mode, where the transition from a layer-by-layer growth mode to an island growth mode is easier over Cu, Ag, and Au UBMs.

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“…There are reports on bonding schemes for 3D integration that deploy a thin Sn layer as an intermediate layer for Cu/Sn/Cu bump bonding structure. However, the temperature required for this technology is still within the range of 200-350 • C. 11,12 Here we report the method of using electrodeposited Ni cone layer in low-temperature bonding between Sn-capped Cu pillar bumps and substrate chip, as shown in Fig. 1a.…”

mentioning

confidence: 99%

Low-Temperature Solid State Bonding of Sn and Nickel Micro Cones for Micro Interconnection

Chen¹,

Luo²,

Hang³

et al. 2012

ECS Solid State Letters

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This paper reports a low-temperature solid state bonding method for potential use in advanced electronic packaging, especially in 3D integration applications. Electrodeposited Ni micro cones with an Au anti-oxidation layer were fabricated and utilized to bond with Sn-capped Cu bumps with the help of appropriate temperature and pressure. Bonding joints were shear tested to evaluate the joint strength of samples bonded at each pressure, with results comparable to reflow soldering. Microscopic observation showed sufficient insertion between Sn and cone-structured Ni, as well as atomic scale bonding between two metals.Three-dimensional integration is being widely studied, interconnect bonding technology improvement is gaining particular interest as a key enabling factor. Requirements for higher vertical I/O density and component complexity necessitate the innovation of general interconnect bonding methods. Considered as one of the most important technical trends that enables advanced packaging, low-temperature bonding is being widely developed, 1-5 with the advantages including dramatically reduced processing temperature, high density and simple post processing. The method of thermocompression is commonly used in realization of low-temperature bonding, mostly based on the atomic level inter-diffusion of metals at solid state. Both direct metal-metal bonding and intermediate-assisted bonding through thermocompression were reported. 6-8 Generally the direct metal-metal bonding or diffusion bonding needs an activated bonding surface with large contact area enabled by the surface finishing processes like polishing and high energy irradiation. For example, the most highlighted Cu-Cu bonding, 7,9,10 requires either temperature usually higher than 300 • C or highly flat, clean surface, and compatibility with existing interconnect technology makes it difficult for massive applications at present.With the extensive use of innovative bonding technologies expected in the near future, the alleviation of bonding temperature and pressure, as well as the reduction of process complexity and cost, will be constantly pursued. There are reports on bonding schemes for 3D integration that deploy a thin Sn layer as an intermediate layer for Cu/Sn/Cu bump bonding structure. However, the temperature required for this technology is still within the range of 200-350 • C. 11,12 Here we report the method of using electrodeposited Ni cone layer in low-temperature bonding between Sn-capped Cu pillar bumps and substrate chip, as shown in Fig. 1a. This technique is carried out in air with no flux needed and keeps solid state throughout. Sn is a soft metal; when temperature elevates, its hardness further decreases, resulting in an increase in strain rate and creep rate under compressive load. [13][14][15][16] The mechanical property difference between Sn and other rigid metals thus can be exploited for mechanical insertion realized by compressive deformation. The electrodeposited Ni micro-cone layer is chosen as the bonding mate here for its special...

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Introduction of an Electroless-Plated Ni Diffusion Barrier in Cu/Sn/Cu Bonding Structures for 3D Integration

Cited by 15 publications

References 13 publications

Effect of Surface Roughness and Electroless Ni–P Plating on the Bonding Strength of Bi–Te-based Thermoelectric Modules

Effect of Surface Roughness and Electroless Ni–P Plating on the Bonding Strength of Bi–Te-based Thermoelectric Modules

Effects of Under Bump Metallurgy (UBM) Materials on the Corrosion of Electroless Nickel Films

Low-Temperature Solid State Bonding of Sn and Nickel Micro Cones for Micro Interconnection

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