Behavior of Plated Microbumps during Ultrasonic Flip-Chip Bonding Determined from Dynamic Strain Measurement

Watanabe, Naoya; Asano, Tanemasa

doi:10.1143/jjap.42.2193

Cited by 19 publications

(4 citation statements)

References 4 publications

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“…Among the various forms of the SiP, the stacked three-dimensional SiP, which forms penetrating electrodes through the chip and connects the upper and lower chips by narrow-pitch bumps of Au or Cu, is suited for high-speed operation, and thus has been actively studied [5][6][7]. In a three-dimensional stacked SiP, the chips to be stacked should be thinned to a thickness of several dozen micrometers, considering the wiring resistance of the penetrating electrode and the height of the package.…”

Section: Introductionmentioning

confidence: 99%

Mobility change of MOSFETs in a chip-stacked multichip package

Ikeda¹,

Honda²,

Ogi³

et al. 2006

Electron. Comm. Jpn. Pt. II

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We studied the mobility change of MOSFETs in a chip‐stacked multichip package. A 6‐inch wafer that had the back ground to 50 µm thickness was diced into chips and a chip was cemented to a glass epoxy substrate with a nonconductive paste (NCP), and in addition, a second chip was bonded on the first chip in a flip chip arrangement. The interchip connection was made by thermocompression bonding of Au/Ni bumps formed on the upper and lower chips. The MOSFETs on the first chip had not shown changes in mobility before stacking the second chip, but after stacking the chip, the mobility of the pMOSFETs increased and the mobility of the nMOSFETs decreased. Before chip stacking, the first chip had been slightly convex, but after stacking it was deformed to a greatly concave shape. It is considered that the glass epoxy substrate or the NCP had undergone a plastic deformation during the thermocompression bonding of the chip and that the strain from this deformation remained after the thermocompression bonding process. As a consequence, bending compressive stress occurred in the first chip in the [1¯10] direction, and it is considered that the mobility of the MOSFET changed due to the piezoresistive effect. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 89(7): 1– 8, 2006; Published online in Wiley InterScience (http://www.interscience.wiley.com). DOI 10.1002/ecjb.20246

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Section: Introductionmentioning

confidence: 99%

Mobility change of MOSFETs in a chip-stacked multichip package

Ikeda¹,

Honda²,

Ogi³

et al. 2006

Electron. Comm. Jpn. Pt. II

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“…Figure 2(b) shows a cross section of the strain sensor. On the basis of the previous publications, 21,22) the strain sensor has been designed such that it can determine strains along the axis parallel to the direction of ultrasonic vibration and the axis normal to the surface, i.e., in the direction of pressing load. The sensor is composed of a pair of n-and p-type piezoresistance gauges.…”

Section: Experimental Methodsmentioning

confidence: 99%

Bonding dynamics of compliant microbump during ultrasonic bonding investigated by using Si strain gauge

Iwanabe

Nakadozono

Senda

et al. 2016

Jpn. J. Appl. Phys.

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The bonding dynamics of a cone-shaped microbump during ultrasonic bonding are investigated by in situ measurements of the strain generated in a substrate using a piezoresistance strain sensor. The strain sensor is composed of a pair of p- and n-type piezoresistance gauges to extract strain components in the ultrasonic vibration along the plane parallel to the substrate surface and along the direction perpendicular to the surface. Flip-chip bonding is performed at room-temperature. The time evolution of the strain generated in the substrate according to the load-up of pressing force and application of ultrasonic vibration is clearly detected. The softening of the bump metal during the application of ultrasonic vibration is clearly observed. Results of a comparative study between the bonding of a cone-shaped microbump and that of a flat-top microbump suggest mechanical stress concentration near the top end of the cone-shaped microbump, which results in the transformation of the crystal texture of the bump from grains to fine crystallites.

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“…The problem is that an actual bonding surface consists of an oxide film and a machined layer; [3][4][5][6][7] therefore, adhesion between surfaces at the bond interface and removal of the oxide film represent necessary requirements to obtain high bond strength. Recently, ultrasonic vibration, [8][9][10][11][12][13] plasma processing, [14][15][16][17][18][19] and organic acid pretreatment [20][21][22][23] have been investigated as methods for breaking and cleaning a superficial oxide film. Indeed, in a previous study, we showed that modification of an oxide film with formic acid greatly improves the strength of bonding between tin surfaces 22) and between tin and copper.…”

Section: Introductionmentioning

confidence: 99%

Cu/Cu direct bonding by metal salt generation bonding technique with organic acid and persistence of reformed layer

Koyama

Hagiwara

Shohji

2015

Jpn. J. Appl. Phys.

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In this study, the effect of the metal salt generation bonding technique on the strength of a direct-bonded copper–copper interface was investigated. Copper surfaces were modified by boiling in several types of organic acids, and direct bonding was performed at a bonding temperature of 423–673 K under a load of 588 N (for a bonding time of 0.9 ks). As a result of the surface modification, bonded joints were obtained at bonding temperatures of 150 K (after treatment with formic acid) and 100 K (after citric acid treatment) lower than that required for the unmodified surfaces. In addition, the duration of the modification effects was investigated by exposing the modified surface to an air atmosphere furnace kept at 323 K. The bonding strength of the citric acid-modified surface remained unchanged even after 168 h, whereas that of the surface modified with formic acid decreased within 6 h.

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Behavior of Plated Microbumps during Ultrasonic Flip-Chip Bonding Determined from Dynamic Strain Measurement

Abstract: The effect of moderate viscosity is of the same type for sound waves and for surface waves striking.

Cited by 19 publications

References 4 publications

Mobility change of MOSFETs in a chip-stacked multichip package

Mobility change of MOSFETs in a chip-stacked multichip package

Bonding dynamics of compliant microbump during ultrasonic bonding investigated by using Si strain gauge

Cu/Cu direct bonding by metal salt generation bonding technique with organic acid and persistence of reformed layer

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