Browsing by Author "Tu, KN"

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Electromigration in pb-free SnAg3.8Cu0.7 solder stripes
(2005-08-01)
Hsu, YC
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Chou, CK
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Liu, PC
;
Chen, C
;
Yao, DJ
Electromigration behavior in the eutectic SnAg3.8Cu0.7 solder stripes was investigated in the vicinity of the device operation temperature of 100 degrees C by using the edge displacement technique. Measurements were made for relevant parameters for electromigration of the solder, such as drift velocity, threshold current density, activation energy, as well as the product of diffusivity and effective charge number (DZ(*)). The threshold current densities were estimated to be 4.3x10(4) A/cm(2) at 80 degrees C, 3.2x10(4) A/cm(2) at 100 degrees C, and 1.4x10(4) A/cm(2) at 120 degrees C. These values represent the maximum current densities that the SnAg3.8Cu0.7 solder can carry without electromigration damage at the three stressing temperatures. The electromigration activation energy was determined to be 0.45 eV in the temperature range of 80-120 degrees C. The measured products of diffusivity and the effective charge number, DZ(*), were -1.8x10(-10) cm(2)/s at 80 degrees C, -5.0x10(-10) cm(2)/s at 100 degrees C, and -7.2x10(-10) cm(2)/s at 120 degrees C. (c) 2005 American Institute of Physics.
Enhanced dopant activation and elimination of end-of-range defects in BF2+-implanted silicon-on-insulator by high-density current
(2001-12-10)
Lin, HH
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Cheng, SL
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Chen, LJ
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Chen, C
;
Tu, KN
Enhanced dopant activation and elimination of end-of-range (EOR) defects in BF2+-implanted silicon-on-insulator (SOI) have been achieved by high-density current stressing. With the high-density current stressing, the implantation amorphous silicon underwent recrystallization, enhanced dopant activation and elimination of the (EOR) defects. The current stressing method allows the complete removal of EOR defects that has not been possible with conventional thermal annealing in the processing of high-performance SOI devices. (C) 2001 American Institute of Physics.
Relieving the current crowding effect in flip-chip solder joints during current stressing
(2006-01-01)
Liang, SW
;
Shao, TL
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Chen, C
;
Yeh, ECC
;
Tu, KN
Three-dimensional simulations for relieving the current crowding effect in solder joints under current stressing were carried out using the finite element method. Three possible approaches were examined in this study, including varying the size of the passivation opening, increasing the thickness of Cu underbump metallization (UBM), and adopting or inserting a thin highly resistive UBM layer. It was found that the current crowding effect in the solder bump could be successfully relieved with the thick Cu UBM or with the highly resistive UBM. Compared to the solder joint with Al/Ni(V)/Cu UBM, for instance, the maximum current density in a solder bump decreased dramatically by a factor of fifteen, say from 1.11 x 10(5) A/cm(2) to 7.54 x 10(3) A/cm(2) when a 20-pm-thick Cu UBM was used. It could be lowered by a factor of seven, say to 1.55 x 10(4) A/cm(2), when a 0.7-mu m UBM of 14770 mu Omega cm was adopted. It is worth noting that although a resistive UBM layer was used, the penalty on overall resistance increase was negligible because the total resistance was dominated by the Al trace instead of the solder bump. Thermal simulation showed that the average temperature increase due to Joule heating effect was only 2.8 degrees C when the solder joints with UBM of 14770 mu Omega cm were applied by 0.2 A.
Threshold current density of electromigration in eutectic SnPb solder
(2005-05-16)
Yeh, YT
;
Chou, CK
;
Hsu, YC
;
Chen, C
;
Tu, KN
Electromigration has emerged as an important reliability issue in the microelectronics packaging industry since the dimension of solder joints has continued to shrink. In this letter, we report a technique that enables the precise measurement of the important parameters of solder electromigration, such as activation energy, critical length, threshold current density, effective charge numbers, and electromigration rate. Patterned Cu/Ti films in a Si trench were employed for eutectic SnPb solder to be reflowed on, and thus solder Blech specimens were fabricated. Atomic force microscope was used to measure the depletion volume caused by electromigration on the cathode end. The threshold current density is estimated to be 8.5x10(3) A/cm(2) at 100 degrees C, which relates directly to the maximum allowable current that a solder joint can carry without electromigration damage. This technique facilitates the scientifically systematic investigation of electromigration in solders. (c) American Institute of Physics.