Browsing by Author "Hsiao, Hsiang-Yao"

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Direct measurement of hot-spot temperature in flip-chip solder joints under current stressing using infrared microscopy
(2008-08-01)
Hsiao, Hsiang-Yao
;
Liang, S. W.
;
Ku, Min-Feng
;
Chen, Chih
;
Yao, Da-Jeng
Several simulation studies reported that a hot spot exists in flip-chip solder bumps under accelerated electromigration. Yet, there are no experimental data to verify it. In this paper, the temperature distribution during electromigration in flip-chip SnAg3.5 solder bumps is directly inspected using infrared microscopy. Two clear hot spots are observed in the bump. One is located at the region with peak current density and the other one is at the bump edge under the current-feeding metallization on the chip side. Under a current stress of 1.06x10(4) A/cm(2), the temperature in the two hot spots are 161.7 and 167.8 degrees C, respectively, which surpass the average bump temperature of 150.5 degrees C. In addition, the effect of under-bump-metallization (UBM) thickness on the hot spots is also examined. It indicates that the hot-spot temperature in the solder bump increases for the solder joints with a thinner UBM. Electromigration test indicates that these hot spots have significant influence on the initial failure location. (c) 2008 American Institute of Physics.
Erratum: "Thermomigration in flip-chip SnPb solder joints under alternate current stressing" [Appl. Phys. Lett. 90, 152105 (2007)]
(2007-06-11)
Hsiao, Hsiang-Yao
;
Chen, Chih
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Extremely anisotropic single-crystal growth in nanotwinned copper
(2014-10-01)
Lu, Chia-Ling
;
Lin, Han-Wen
;
Liu, Chien-Min
;
Huang, Yi-Sa
;
Lu, Tien-Lin
By electroplating of nearly unidirectionally < 111 >-oriented nanotwinned and fine-grained Cu on a Si wafer surface followed by annealing at 400-500 degrees C for up to 1 h, we grew many extremely large < 100 >-oriented single crystals of Cu with sizes ranging from 200 to 400 mu m. By patterning and annealing the nanotwinned Cu films, we grew an array of < 100 >-oriented single crystals of Cu with sizes ranging from 25 to 100 mu m on Si. In comparison, single-crystal nano-wire growth is a one-dimensional anisotropic growth process, in which the growth along the axial direction is much faster than in the radial direction. We report here a bulk-type two-dimensional crystal growth of an array of numerous < 100 >-oriented single crystals of Cu on Si. This growth process has the potential for microbump applications in three-dimensional integrated circuit-packaging technology for hand-held consumer electronic products.
Fabrication and Characterization of (111)-Oriented and Nanotwinned Cu by Dc Electrodeposition
(2012-10-01)
Liu, Tao-Chi
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Liu, Chien-Min
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Hsiao, Hsiang-Yao
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Lu, Jia-Ling
;
Huang, Yi-Sa
We report an approach to fabricating (111)-oriented and nanotwinned Cu (nt-Cu) by dc electroplating. A 200 nm thick Cu with (111) preferred orientation is required as a seed layer. Highly oriented Cu films with densely packed nanotwins can be grown to exceed 20 mu m thick at high current and high stirring speeds. X-ray diffraction indicates that the intensity ratio of (111) to (220) is as high as 506, which is the highest among the reported electroplated Cu films. The spacing of twins ranges from 10 to 100 nm, which reveals a high hardness value of 2.23 GPa. The (111)-oriented nt-Cu will have many potential applications in interconnects and 3D IC packaging.
Fabrication of arrays of (100) Cu under-bump-metallization for 3D IC packaging
(2015)
Chiu, Wei-Lan
;
Lu, Chia-Ling
;
Lin, Han-Wen
;
Liu, Chien-Min
;
Huang, Yi-Sa
Due to the thousands of microbumps on a chip for 3D ICs, the precise control of the microstructure of all the material is required. The nearly < 111 >-oriented nanotwinned and fine-grained Cu was electroplated on a Si wafer surface and annealed at 400-500 C for 1 h, many extremely large < 100 > oriented Cu crystals with grain sizes ranging from 200 to 400 um were obtained. The < 111 >-oriented Cu grains were transformed into super-large < 100 >-oriented grains after the annealing. In addition, we patterned the < 111 >-oriented Cu films into pad arrays of 25 to 100 um in diameter and annealed the nanotwinned Cu pads with same conditions. An array of < 100 >-oriented single crystals Cu pads can be obtained. Otherwise, single-crystal nano wire growth displays a process by one-dimensional anisotropic growth, in which the growth along the axial direction is much faster than in the radial direction. This study reported here a bulk-type two-dimensional crystal growth of an array of numerous < 100 >-oriented single crystals of Cu on Si. The growth process in 3D IC has the potential for microbump applications packaging technology.
Measurement of Temperature Distribution in SnAg3.5 Flip-Chip Solder Joints during Current Stressing Using Infrared Microscopy
(2008)
Hsiao, Hsiang-Yao
;
Chen, Chih
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this paper, the temperature distribution during electromigration in flip-chip SnAg3.5 solder bumps is directly examined using infrared microscopy. Two clear hot spots are observed in the bump. One is located at the region with peak current density, and the other one is at the bump edge under the current-feeding metallization on the chip side. Under a current stress of 1.06 x 10(4) A/cm(2), the temperature in the two hot spots are 161.7 degrees C and 167.8 degrees C, respectively, which surpass the average bump temperature of 150.5 degrees C. In addition, effect Of under-bump-metallization (UBM) thickness oil the hot spots is also examined. It indicates that the hot-spot temperature in the solder bump increases for the solder joints with a thinner UBM.
Measurement of Temperature Distribution in SnAg3.5 Flip-Chip Solder Joints during Current Stressing Using Infrared Microscopy
(2008-01-01)
Hsiao, Hsiang-Yao
;
Chen, Chih
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Several simulation studies reported that a hot spot exists in flip-chip solder bumps under accelerated electromigration. Yet, there are no experimental data to verify it. In this paper, the temperature distribution during electromigration in flip-chip SnAg3.5 solder bumps is directly inspected using infrared microscopy. Two clear hot spots are observed in the bump. One is located at the region with peak current density, and the other one is at the bump edge under the current-feeding metallization on the chip side. Under a current stress of 1.06 x 10(4) A/cm(2), the temperature in the two hot spots are 161.7 degrees C and 167.8 degrees C, respectively, which surpass the average bump temperature of 150.5 degrees C. In addition, effect of under-bump-metallization (UBM) thickness oil the hot spots is also examined. It indicates that the hot-spot temperature in the solder bump increases for the solder joints with a thinner UBM. Electromigration test indicates that these hot spots have significant influence oil the initial failure location.
Nonuniform and Negative Marker Displacements Induced by Current Crowding During Electromigration in Flip-Chip Sn-0.7Cu Solder Joints
(2009-12-01)
Liang, S. W.
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Hsiao, Hsiang-Yao
;
Chen, Chih
;
Xu, Luhua
;
Tu, K. N.
A quantitative analysis of the nonuniform distribution of current density and nonuniform rate of electromigration has been carried out by measuring the movement of an array of diffusion markers. Tiny marker arrays were fabricated by focused ion beam on the polished surface of flip-chip solder joints near the anode to measure the electromigration rate. The marker velocity at the current-crowding region was found to be at least five times larger than at locations far from the region. Some of the markers in the low-current-density region possess negative velocities, indicating that backflow occurs during the electromigration. The backflow, in which the atomic flow is against the electron flow, is explained by a constant-volume model as well as the back-stress induced by electromigration.
Thermomigration in flip-chip SnPb solder joints under alternating current stressing
(2007-04-09)
Hsiao, Hsiang-Yao
;
Chen, Chih
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Thermomigration in flip-chip solder joints is investigated using alternating currents and infrared microscopy to decouple it from electromigration effect. It is found that the thermal gradient in solder bump can be as high as 2143 degrees C/cm when 9.2x10(4) A/cm(2) was applied at 100 degrees C. Markers fabricated by focus ion beam are employed to measure the thermomigration rate. The thermomigration flux is measured to be 3.3x10(13) at./cm(2). With the known thermal gradient, the molar heat of 26.8 kJ/mole has been obtained for the transport of Pb. (c) 2007 American Institute of Physics.
Thermomigration in Pb-free SnAg solder joint under alternating current stressing
(2009-03-02)
Hsiao, Hsiang-Yao
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Chen, Chih
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Lead-free solders have been adopted by the microelectronics industry. However, their thermomigration behaviors are unclear. Thermomigration in eutectic SnAg3.5 solder joints was investigated using an alternating current (ac) of 0.57 A at 100 degrees C. The ac eliminates the electromigration effect and creates a thermal gradient of 2829 degrees C/cm, facilitating the study of thermomigration. Arrays of tiny markers fabricated by a focused ion beam are employed to measure the thermomigration rate. It is found that Sn atoms migrated toward the hot end. The thermomigration flux and molar heat of transport are measured to be 5.0x10(12) atoms/cm(2) and 1.36 kJ/mole, respectively.
Thermomigration in solder joints
(2012-09-01)
Chen, Chih
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Hsiao, Hsiang-Yao
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Chang, Yuan-Wei
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Ouyang, Fanyi
;
Tu, K. N.
In 3D IC technology, the vertical interconnection consists of through-Si-vias (TSV) and micro solder bumps. The size of the micro-bump is approaching 10 mu m, which is the diameter of TSV. Since joule heating is expected to be the most serious issue in 3D IC, heat flux must be conducted away by temperature gradient. If there is a temperature difference of 1 degrees C across a micro-bump, the temperature gradient will be 1000 degrees C/cm, which can cause thermomigration at the device operation temperature around 100 degrees C. Thus thermomigration will become a very serious reliability problem in 3D IC technology. We review here the fundamentals of thermomigration of atoms in microbump materials; both molten state and solid state thermomigration in solder alloys will be considered. The thermomigration in Pb-containing solder joints is discussed first. The Pb atoms move to the cold end while Sn atoms move to the hot end. Then thermomigration in Pb-free SnAg solder joints is reviewed. The Sn atoms move to the hot end, but the Ag atoms migrate to the cold end. Thermomigration of other metallization elements, such as Cu, Ti and Ni is also presented in this paper. In solid state, copper atoms diffuse rapidly via interstitially to the cold end, forming voids in the hot end. In molten state, Cu thermomigration affects the formation of intermetallic compounds. (c) 2012 Elsevier B.V. All rights reserved.
Transition from flip chip solder joint to 3D IC microbump: Its effect on microstructure anisotropy
(2013-01-01)
Tu, K. N.
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Hsiao, Hsiang-Yao
;
Chen, Chih
;
材料科學與工程學系
;
Department of Materials Science and Engineering
As microelectronic industry develops 3D IC on the basis of through-Si-vias (TSV) technology, the processing and reliability of microbumps, which are used to interconnect the stacking chips, is being actively investigated. Due to the reduction in size of microbumps, the diameter is about one order of magnitude smaller than that of flip chip solder joints, and the volume is 1000 times smaller. Its microstructure and in turn its properties will be anisotropic because the number of grains in a microbump becomes very small. Its statistical failure will have a wide distribution because of anisotropy, including early failure. This review addresses this issue and the remedy. (C) 2012 Elsevier Ltd. All rights reserved.
Unidirectional Growth of Microbumps on (111)-Oriented and Nanotwinned Copper
(2012-05-25)
Hsiao, Hsiang-Yao
;
Liu, Chien-Min
;
Lin, Han-Wen
;
Liu, Tao-Chi
;
Lu, Chia-Ling
Highly oriented [111] Cu grains with densely packed nanotwins have been fabricated by direct-current electroplating with a high stirring rate. The [111]-oriented and nanotwinned Cu (nt-Cu) allow for the unidirectional growth of Cu6Sn5 intermetallics in the microbumps of three-dimensional integrated-circuit packaging; a uniform microstructure in a large number of microbumps of controlled orientation can be obtained. The high-density twin boundaries in the nt-Cu serve as vacancy sinks during the solid-state reaction between Pb-free solder and Cu and greatly reduce the formation of Kirkendall (or Frenkel) voids.