Browsing by Author "Lin, Benson"

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Chip-to-chip copper direct bonding in no-vacuum ambient using (111) oriented nano-twinned copper
(2018-01-01)
Juang, Jing Ye
;
Shie, Kai Cheng
;
Li, Yu Jin
;
Lin, Benson
;
Chang, Chia Cheng
In this study, we demonstrate the chip-to-chip copper direct bonding by using (111) oriented nano-twinned copper in N-2 ambient, without vacuum. A well bonded interface in the Cu-to-Cu joint was identified by the focus ion beam (FIB) microstructure observation. The secondary electron images (SEI) showed a void-less bonding interface within the bonded Cu joint. In addition, a die shear test was conducted. The test result revealed that the Cu joint has a robust bonded Cu structure due to its high value. The shear strength is more than 100 MPa. There is nearly twice strength value higher than the traditional SnAg solder joint (64 MPa). In addition, the scanning electron microscope (SEM) image showed the joint fractured in a ductile manner. Besides, we also performed the resistance measurement by using Kelvin probes on the bonded chip-to-chip test vehicle. The result showed 4.12 m Omega in single joint resistance and 4.26 x 10(-8) Omega.cm(2) in contact resistivity. More than 30% resistance reduction has been confirmed as compared to the traditional SnAg solder joint (6.32 m Omega). Moreover, for further post annealing process on the bonded test vehicle, we can further reduce the joint resistance by the value of 2.9 m Omega. It approaches the value of bulk Cu. The evidences revealed that the Cu-to-Cu joint is superior to the traditional SnAg solder. In last, the chip-to-chip copper direct bonding by using (111) oriented nano-twinned copper in N-2 ambient was achieved.
High Electromigration Lifetimes of Nanotwinned Cu Redistribution Lines
(2019-01-01)
Tseng, I-Hsin
;
Li, Yu-Jin
;
Lin, Benson
;
Chang, Chia-Cheng
;
Chen, Chih
In this paper, we measured the electromigration lifetimes for nanotwinned copper (nt-Cu) and regular copper redistribution lines (RDLs) for 3D-ICs packaging. The width of the RDLs is 10 mu m in width and 5 mu m in thickness, and the lines were coated by polyimide. The average lifetime of the nt-Cu RDL copper line is 445 hours to reach 1.2 times of its initial resistance. However, it takes 160 hours to reach the same resistance increase for regular copper RDL line. The nt-Cu has better EM lifetime than regular copper.
High-toughness (111) nano-twinned copper lines for fan-out wafer-level packaging
(2019-01-01)
Li, Yu-Jin
;
Hsu, Wei-Yu
;
Lin, Benson
;
Chang, ChiaCheng
;
Chen, Chih
In the present paper, the nt-Cu were electroplated on the InFO test vehicles with 5 mu m line width to compare the reliability with the normal electroplated copper. The temperature of the TCT ranges from -55 to 125 degrees C. The microstructure of the copper traces after 200 cycles and 1000 cycles was shown in the results. The nt-Cu RDL is much stronger than the normal Cu in the thermal cycling test. In order to understand the mechanical property of the nt-Cu and the normal Cu, tensile tests of electroplated copper foils was employed. After annealing at 250 degrees C for 3 hours, the toughness of nt-Cu (about 60MJ/m(3)) is much higher than normal copper (about 30MJ/m(3)). In addition, the simulation results shows that the maximum stress on the copper trace during the TCT is about 200MPa which is much lower than the yield point of nt-Cu. In other word, the nt-Cu would return to original size when the stress removed without strain accumulation. In summary, we observed that the nt-Cu performs much better than normal copper in TCT. From the tensile test and simulation, we can understand the mechanical behavior and the typical reason for the high reliability of nt-Cu.
Highly (111)-oriented Nanotwinned Cu for High Fatigue Resistance in fan-out wafer-level packaging
(2019-01-01)
Li, Yu-Jin
;
Theng, Chih-Han
;
Tseng, I-Hsin
;
Chen, Chih
;
Lin, Benson
Fanout wafer level packaging is a potential solution for combining high electrical performance and low cost. However, with the shrinkage of the package, the mechanical reliability of the copper redistribution layer becomes an important issue. However, based on the processing of fan out packaging, the copper lines were annealed several times during the process. The annealing process is harmful to traditional strengthen mechanisms, but not to columnar grains with high density twinning structure. In this study, the technology of electroplating highly <111>-oriented copper lines was introduced to solve the reliability issue in copper RDLs. By the nature of nano-twinned Cu, the performance of thermal cycling test (TCT) lifetime is much better than normal copper, and the failure mechanisms were discussed in this study.