Browsing by Author "Lin, Han-Wen"

Now showing 1 - 10 of 10

Effect of grain orientations of Cu seed layers on the growth of < 111 >-oriented nanotwinned Cu
(2014-08-19)
Liu, Chien-Min
;
Lin, Han-Wen
;
Lu, Chia-Ling
;
Chen, Chih
;
材料科學與工程學系
We investigate the growth of Cu films on two different Cu seed layers: one with regular < 111 >-oriented grains and the other with very strong < 111 >-preferred orientation. It is found that densely-packed nanotwinned Cu (nt-Cu) can be grown by pulsed electroplating on the strong < 111 >-oriented Cu seed layer without a randomly-oriented transition layer between the nt-Cu and the Cu seed layer. The electroplated nt-Cu grow almost epitaxially on the seed layer and formed < 111 >-oriented columnar structures. However, with the regular < 111 >-oriented Cu seed, there is a randomly-oriented transition layer between the nt-Cu and the regular < 111 >-oriented Cu seed. The results indicate that the seed layer plays a crucial role on the regularity of < 111 >-oriented nanotwinned Cu.
Electromigration in microbumps with Cu-Sn intermetallic compounds
(2016)
Chu, Yi-Cheng
;
Zhan, Chau-Jie
;
Lin, Han-Wen
;
Huang, Yu-Wei
;
Chen, Chih
The electromigration test of the microbump interconnects with Cu/Cu6Sn5/Cu structure is reported in this study. This Cu6Sn5 intermetallic compound layer was single-crystal like. The diameter of the microbumps in die-to-die stacking was 30 mu m. Test vehicles were applied by a current density of 2.2x10(5) A/cm(2) and settled on a hotplate at 150 degrees C. The resistances of the microbumps were simultaneously monitored by the four point probe during the test procedure. The Cu6Sn5 transformed into Cu3Sn in the early stage and porous Cu3Sn generated in the Cu6Sn5 layer at later stages. The morphology of porous Cu3Sn could be caused by the current direction. The decomposition of Cu6Sn5 into Cu3Sn and Sn occurs during the EM test. The migration of Sn atoms to the periphery of the under-bump-metallization was forced by the current stress, which may be the mechanism of the pore formation with the pore volume of 41.4%. More porous Cu3Sn was found in the cathode end which was an evidence of the EM effect. Finite element analysis was used to do some calculation based on theoretical stoichiometry and microstructures in the test results. The resistivity of porous Cu3Sn structure which was about 30 mu Omega-cm which was three times larger than that of Cu3Sn. The porous Cu3Sn may threaten the reliability issues of microbumps.
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 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.
LOW-TEMPERATURE AND LOW-PRESSURE DIRECT COPPER-TO-COPPER BONDING BY HIGHLY (111)-ORIENTED NANOTWINNED CU
(2016)
Chen, Chih
;
Liu, Chien-Min
;
Lin, Han-Wen
;
Huang, Yi-Sa
;
Chu, Yi-Cheng
As the size of microbumps continues to shrink, the amount of solder decreases gradually, resulting the brittleness of solder joints due to formation of intermetallic compounds. Low-temperature Cu-to-Cu direct bonding appears to be one of the solutions for fine-pitch microbumps for 3D IC packaging. However, the high bonding temperature and pressure are the main problems of this approach. We achieve low-temperature Cu-to-Cu direct bonding at low pressure and ordinary vacuum. In addition, the cleaning process is simple. To bond the electroplated Cu films, the samples were cut into 3 x 3-mm(2) pieces. Then, the pieces were cleaned in acetone for 5 min, dried with a N-2 purge, cleaned with a mixed solution of HCl and deionized water (DI) water for 30 sec, rinsed with DI water, and purged with N-2 gas again. The bonding temperature can be lowered to 150 degrees C at a compressive stress of 114 psi held for 60 min at 10-3 torr, or at 200 degrees C at for 30 min. The temperature is lower than the reflow temperature of 250 degrees C for most Pb-free solders. We achieve low-temperature bonding using electroplate highly (111)-oriented nanotwinned Cu (nt-Cu) films. Excellent bonding interface can be accomplished by bonding two highly (111)-oriented nt-Cu films. In addition, excellent interface with few voids can be achieved between a highly (111)-oriented nt-Cu film and a randomly-oriented Cu film. Our breakthrough is based on the finding that the (111) orientation of the Cu surface is critical for bonding. The diffusivity of Cu atoms on (111) surfaces is approximately 3-4 orders higher than other major planes. The (111) plane allows for fast surface diffusion, which enables low-temperature creep to occur. The bonded interface between two (111) surfaces forms a twist-type grain boundary (GB). If the GB has a low angle, it has a hexagonal network of screw dislocations. The hexagonal network image was obtained by plan-view transmission electron microscopy. A simple kinetic model of surface creep will be presented. Our breakthrough provide a potential solution with a huge impact to the interconnect materials in 3D IC. The detail results will be presented in the conference.
Low-temperature direct copper-to-copper bonding enabled by creep on (111) surfaces of nanotwinned Cu
(2015-05-12)
Liu, Chien-Min
;
Lin, Han-Wen
;
Huang, Yi-Sa
;
Chu, Yi-Cheng
;
Chen, Chih
Direct Cu-to-Cu bonding was achieved at temperatures of 150-250 degrees C using a compressive stress of 100 psi (0.69 MPa) held for 10-60 min at 10(-3) torr. The key controlling parameter for direct bonding is rapid surface diffusion on (111) surface of Cu. Instead of using (111) oriented single crystal of Cu, oriented (111) texture of extremely high degree, exceeding 90%, was fabricated using the oriented nano-twin Cu. The bonded interface between two (111) surfaces forms a twist-type grain boundary. If the grain boundary has a low angle, it has a hexagonal network of screw dislocations. Such network image was obtained by plan-view transmission electron microscopy. A simple kinetic model of surface creep is presented; and the calculated and measured time of bonding is in reasonable agreement.
Low-temperature direct copper-to-copper bonding enabled by creep on highly (111)-oriented Cu surfaces
(2014-05-01)
Liu, Chien-Min
;
Lin, Han-Wen
;
Chu, Yi-Cheng
;
Chen, Chih
;
Lyu, Dian-Rong
We achieve low-temperature Cu-to-Cu direct bonding using highly (1 1 1)-orientated Cu films. The bonding temperature can be lowered to 200 degrees C at a stress of 114 psi for 30 min at 10(-3) torr. The temperature is lower than the reflow temperature of 250 degrees C for Pb-free solders. Our breakthrough is based on the finding that the Cu (1 1 1) surface diffusivity is the fastest among all the planes of Cu and the bonding process can occur through surface diffusion creep on the (1 1 1) surfaces. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Novel EBSD preparation method for Cu/Sn microbumps using a focused ion beam
(2012-12-01)
Liu, Tao-Chi
;
Chen, Chih
;
Chiu, Kuo-Jung
;
Lin, Han-Wen
;
Kuo, Jui-Chao
We proposed a novel technique developed from focused ion beam (FIB) polishing for sample preparation of electron backscatter diffraction (EBSD) measurement. A low-angle incident gallium ion beam with a high acceleration voltage of 30 kV was used to eliminate the surface roughness of cross-sectioned microbumps resulting from mechanical polishing. This work demonstrates the application of the FIB polishing technique to solders for a high-quality sample preparation for EBSD measurement after mechanical polishing. (C) 2012 Elsevier Inc. All rights reserved.
Thermomigration of Ti in flip-chip solder joints
(2012-05-01)
Chen, Hsiao-Yun
;
Lin, Han-Wen
;
Liu, Chien-Min
;
Chang, Yuan-Wei
;
Huang, Annie T.
Titanium has a very large heat of transport value of -768 kJ mol(-1). However, thermomigration of Ti in solder joints has not been examined. In this study, void formation was observed in non-current-stressed Al traces during electromigration and thermomigration tests of SnAg solder joints. Voids formed inside the traces located above the solder bumps with no current flow. We found that Ti thermomigration occurred in the joint, resulting in the reaction of Al and Cu, leaving voids behind in the Al trace. (C) 2012 Acta Materialia Inc. Published by 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.