Characterization of interfacial structure for low-temperature direct bonding of Si substrates sputtered with Ag nanotwinned films

Lai, Yu-Chang; Wu, Po‐Ching; Chuang, Tung‐Han

doi:10.1016/j.matchar.2021.111060

Cited by 16 publications

(6 citation statements)

References 24 publications

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“…The progressive evolution of interfacial voids in those joints has been identified [ 25 ]. Most of the previous studies qualitatively examined interfacial bonding using cross-sectional imaging [ 8 , 11 , 12 , 23 , 26 , 27 , 28 ]. Those studies did not provide detailed information on interfacial voids in terms of shape, size, location, and distribution.…”

Section: Introductionmentioning

confidence: 99%

Interfacial Characterization of Low-Temperature Cu-to-Cu Direct Bonding with Chemical Mechanical Planarized Nanotwinned Cu Films

et al. 2022

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Copper-to-copper (Cu-to-Cu) direct bonding is a promising approach to replace traditional solder joints in three-dimensional integrated circuits (3D ICs) packaging. It has been commonly conducted at a temperature over 300 °C, which is detrimental to integrated electronic devices. In this study, highly (111)-oriented nanotwinned (nt) Cu films were fabricated and polished using chemical mechanical planarization (CMP) and electropolishing. We successfully bonded and remained columnar nt-Cu microstructure at a low temperature of 150 °C thanks to the rapid diffusion of Cu on (111) surface. We employed a new microstructural method to characterize quantitatively the interfacial bonding quality using cross-sectional and plan-view microstructural analyses. We discovered that CMP nt-Cu bonding quality was greater than that of electropolished nt-Cu ones. The CMP nt-Cu films possessed extremely low surface roughness and were virtually free of pre-existing interface voids. Thus, the bonding time of such CMP nt-Cu films could be significantly shortened to 10 min. We expect that these findings may offer a pathway to reduce the thermal budget and manufacturing cost of the current 3D ICs packaging technology.

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Section: Introductionmentioning

confidence: 99%

Interfacial Characterization of Low-Temperature Cu-to-Cu Direct Bonding with Chemical Mechanical Planarized Nanotwinned Cu Films

et al. 2022

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“…Currently, pastes of Ag particles are commonly used for this layer [45][46][47][48]. Sputtered (111)-oriented Ag films are also under investigation [49][50][51][52]. Cu-Sn powders/pastes may also serve as die attach materials because the Cu-Sn reaction rate is very fast and its thermal conductivity is good.…”

Section: Introductionmentioning

confidence: 99%

Effects of Cu/SnAgCu Powder Fraction and Sintering Time on Microstructure and Mechanical Properties of Transient Liquid Phase Sintered Joints

Tran,

Liu,

Chen

2024

Materials

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The effects of the sintering duration and powder fraction (Ag-coated Cu/SnAgCu) on the microstructure and reliability of transient liquid phase sintered (TLPS) joints are investigated. The results show that two main intermetallic compounds (IMCs, Cu6Sn5 and Cu3Sn) formed in the joints. The Cu6Sn5 ratio generally decreased with increasing sintering time, Cu powder fraction, and thermal treatment. The void ratio of the high-Cu-fraction joints decreased and increased with increasing sintering and thermal stressing durations, respectively, whereas the low-Cu-fraction counterparts were stable. We also found that the shear strength increased with increasing thermal treatment time, which resulted from the transformation of Cu6Sn5 and Cu3Sn. Such findings could provide valuable information for optimizing the TLPS process and assuring the high reliability of electronic devices.

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“…In addition to Cu-Cu direct bonding, other metal direct bonding methods have also been reported. It is reported that low temperature Ag-Ag direct bonding was achieved at 150-250 °C in 10-60 min in ordinary vacuum by using high (111)-preferred orientation films with densely-packed nanotwins fabricated by magnetron sputtering [20]. Chang et al also used highly (111)-oriented nanotwinned Ag films to achieve metal bonding in 3 min in air atmosphere at 190/200 °C [21].…”

Section: Introductionmentioning

confidence: 99%

Ultra-Thin Cu Nano-Twinned Films Sputtered On Si Wafers for Low Temperature Hybrid Bonding Of Advanced 3D-IC Packages

Yang,

Chen,

Chen

et al. 2024

IJMMME

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The nanotwinned structure has been attracting a great deal of attention due to its excellent mechanical and electrical properties. In this study, ultra-thin nanotwinned Cu (nt-Cu) films with a thickness of 1.5 μm were fabricated by DC magnetron sputtering with moderate substrate bias. Within these films, an equiaxed-grain transition layer only 100-400 nm thick formed between the nanotwinned region and Si substrate and was observed by focused ion beam (FIB). The XRD and EBSD analyses indicated that the as-deposited nanotwinned films had a strong (111) preferred orientation. The surface roughness of the films, as measured with an atomic force microscope (AFM), was below 10 nm, which was sufficiently smooth for chip bonding at low temperature with minor pressure. Direct bonding of Si chips sputtered with such ultra-thin nt-Cu films with a (111) preferred orientation has been evidenced to yield a sound interface, and this bonding method can be applied for the manufacturing of 3D-IC packages.

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Characterization of interfacial structure for low-temperature direct bonding of Si substrates sputtered with Ag nanotwinned films

Cited by 16 publications

References 24 publications

Interfacial Characterization of Low-Temperature Cu-to-Cu Direct Bonding with Chemical Mechanical Planarized Nanotwinned Cu Films

Interfacial Characterization of Low-Temperature Cu-to-Cu Direct Bonding with Chemical Mechanical Planarized Nanotwinned Cu Films

Effects of Cu/SnAgCu Powder Fraction and Sintering Time on Microstructure and Mechanical Properties of Transient Liquid Phase Sintered Joints

Ultra-Thin Cu Nano-Twinned Films Sputtered On Si Wafers for Low Temperature Hybrid Bonding Of Advanced 3D-IC Packages

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