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dc.contributor.authorChen, Chihen_US
dc.contributor.authorLiu, Chien-Minen_US
dc.contributor.authorLin, Han-Wenen_US
dc.contributor.authorHuang, Yi-Saen_US
dc.contributor.authorChu, Yi-Chengen_US
dc.contributor.authorLyu, Dian-Rongen_US
dc.contributor.authorChen, Kuan-Nengen_US
dc.contributor.authorTu, K. N.en_US
dc.date.accessioned2017-04-21T06:49:38Z-
dc.date.available2017-04-21T06:49:38Z-
dc.date.issued2016en_US
dc.identifier.isbn978-0-9888873-9-8en_US
dc.identifier.urihttp://hdl.handle.net/11536/136272-
dc.description.abstractAs 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.en_US
dc.language.isoen_USen_US
dc.subjectCu-to-Cu direct bondingen_US
dc.subject3D ICen_US
dc.titleLOW-TEMPERATURE AND LOW-PRESSURE DIRECT COPPER-TO-COPPER BONDING BY HIGHLY (111)-ORIENTED NANOTWINNED CUen_US
dc.typeProceedings Paperen_US
dc.identifier.journal2016 PAN PACIFIC MICROELECTRONICS SYMPOSIUM (PAN PACIFIC)en_US
dc.contributor.department材料科學與工程學系zh_TW
dc.contributor.department電子工程學系及電子研究所zh_TW
dc.contributor.departmentDepartment of Materials Science and Engineeringen_US
dc.contributor.departmentDepartment of Electronics Engineering and Institute of Electronicsen_US
dc.identifier.wosnumberWOS:000386185100050en_US
dc.citation.woscount0en_US
Appears in Collections:Conferences Paper