Browsing by Author "Chou, T"

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Electromigration in pb-free SnAg3.8Cu0.7 solder stripes
(2005-08-01)
Hsu, YC
;
Chou, CK
;
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.
Microstructural evolution during electromigration in eutectic SnAg solder bumps
(2005-09-01)
Chen, YH
;
Shao, TL
;
Liu, PC
;
Chen, C
;
Chou, T
Microstructural changes induced, by electromigration were studied in eutectic SnAg solder bumps jointed to under-bump metallization (UBM) of Ti/Cr-Cu/Cu and pad metallization of Cu/Ni/Au. Intermetallic compounds (IMCs) and phase transformations were observed during a current stress of 1 X 104 A/cm(2) at 150 degrees C. On the cathode/ substrate side, some of the (Cu-y,Ni1-y)(6)Sn-5 transformed into (Ni-x,Cu1-x)(3)Sn-4 due to depletion of Cu atoms caused by the electron flow. It is found that both the cathode/ chip and anode/chip ends could be failure sites. On the cathode/chip side, the UBM dissolved after current stressing for 22 h, and failure may occur due to depletion of solder. On the anode/chip side, a large amount of (Cu-y,Ni1-y)(6)Sn-5 or (Ni-x,Cu1-x)(3)Sn-4 IMCs grew at the low-current-density area due to the migration of Ni and Cu atoms from the substrate side, which may be responsible for the electromigration failure at this end.
The orientation effect of silicon grains on diamond deposition
(2005-11-01)
Su, YH
;
Chang, L
;
Chen, HG
;
Yan, JK
;
Chou, T
Diamond deposition on mirror-polished polycrystalline silicon substrates which have grains in various orientations has been investigated using electron backscatter diffraction (EBSD) method with scanning electron microscopy (SEMI). Diamond was deposited by microwave plasma chemical vapor deposition with application of a negative bias voltage oil the substrate. The evidence from systematic SEM observations shows that silicon orientation determined by EBSD has a strong effect on diamond nucleation. In general, the diamond nucleation density on Si grains oriented close to < 100 > is the highest, while it is the lowest for those grains close to < 111 >, under the same experimental conditions for deposition. The same phenomena have been observed in the range of methane concentration from 2% to 4% in hydrogen. (c) 2005 Elsevier B.V. All rights reserved.
Tin whisker growth driven by electrical currents
(2004-06-15)
Liu, SH
;
Chen, C
;
Liu, PC
;
Chou, T
;
材料科學與工程學系
Tin whisker growth was investigated in pure Sn using Blech structure. Blech structure was used to investigate the electromigration behavior in pure tin, in which 5000 Angstrom tin strips were on 700 Angstrom titanium films. Tin whiskers grew on the anode side, and voids were observed on the cathode side after stressing at the current densities of 7.5x10(4) and 1.5x10(5) A/cm(2) at room temperature. To investigate temperature effect, samples are stressed at room temperature and 50 degreesC. The whisker growth rates were estimated to be 3 and 7.7 Angstrom/s at room temperature and at 50 degreesC, respectively, in the current density of 1.5x10(5) A/cm(2). The whisker growth rate reduced to 0.4 Angstrom/s at the current density of 7.5x10(4) A/cm(2), which is still faster than that driven by mechanical stress. Transmission electron microscopy results showed that the whiskers are single crystalline and a thin Sn oxide formed on their surfaces. The mechanism of tin whisker growth driven by electrical force is proposed in this article. (C) 2004 American Institute of Physics.