Browsing by Author "Lyu, Dian-Rong"

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A Novel 3D Integration Scheme for Backside Illuminated CMOS Image Sensor Devices
(2014-06-01)
Ko, Cheng-Ta
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Hsiao, Zhi-Cheng
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Chang, Hsiang-Hung
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Lyu, Dian-Rong
;
Hsu, Chao-Kai
A novel backside-illuminated CMOS image sensor (BSI-CIS) scheme and process are developed and demonstrated. This innovative scheme can be realized without fusion oxide bonding and through-silicon via (TSV) fabrication. This wafer-level TSV-less BSI-CIS scheme includes transparent ultrathin silicon (similar to 3.6 mu m) and uses several bonding technologies. The characterization and assessment results indicate that the integration scheme possesses excellent electrical integrity and reliability. In addition, good quality results of the image functional test demonstrate the excellent performance of this scheme. This novel scheme also provides a realizable low-cost solution for the next-generation CIS and further 3-D novel BSI-CIS scheme.
Low-temperature and low pressure copper-to-copper direct bonding enabled by creep on highly (111)-oriented Cu surfaces
(2015)
Tseng, Chih-Han
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Liu, Chien-Min
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Lin, Han-wen
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Chu, Yi-Cheng
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Chen, Chih
Cu-to-Cu microbumps have many advantages, such as better electrical and thermal conductivities. The Cu-to-Cu microbumps may be a potential solution to the heat dissipation problem in 3D IC integration. In addition, for packaging of CMOS image sensors, the bonding temperature is preferred to below 200 degrees C. Therefore, low temperature and low pressure Cu-to-Cu direct is of great interests for packaging industry. However, it is a challenging issue because Cu atoms diffuse slowly below 200 degrees C. In this study, we achieved low temperature and low pressure Cu bonding using highly (111)-orientated Cu films. Because the diffusivity of Cu atoms on the (111) surface diffusivity is the fastest among all the crystallographic planes of Cu. 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. Since the melting points of popular Pb-free solders such as SnAg and SnAgCu are over 230 degrees C. Therefore the present technique can be applied to packaging of CMOS image sensors and 3D IC integration.
LOW-TEMPERATURE AND LOW-PRESSURE DIRECT COPPER-TO-COPPER BONDING BY HIGHLY (111)-ORIENTED NANOTWINNED CU
(2016)
Chen, Chih
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Liu, Chien-Min
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Lin, Han-Wen
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Huang, Yi-Sa
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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
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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.