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Direct bonding of lattice-mismatched and orientationmismatched III-V semiconductor wafers: a step toward establishing "Free-Orientation Integration"
Published in Jong-Chun Woo, Yoon Soo Park, Compound Semiconductors 1995, 2020
On the other hand, the direct bonding is a technique that unites two semiconductor materials without interposing any adhesive [3]. It enables integration of different materials, such as InP and GaAs, without degrading their crystalline quality [4,5]. Integrating GaAs layers with different crystallographic orientations is also reported [6]. Furthermore, integration of InP and GaAs with a change in the relation of their crystallographic axes was shown to work well [7,8]. Therefore, the direct bonding can overcome the two difficulties in epitaxial growth: mismatches in material properties and crystallographic orientations. Consequently, direct bonding will extend the possibilities for device integration. "FreeOrientation Integration" represents a new concept of freely integrating various kinds of material with various crystallographic orientations, which should be implemented by the direct bonding. In order to confirm the applicability of this concept, it should be clarified whether the direct bonding is available for any wafer combinations based on III-V materials. In this paper, therefore, we systematically investigate the direct bonding of various combinations of material and crystallographic orientation in III-V wafers.
Mechanical Properties of Materials in Microstructure Technology
Published in Bharat Bhushan, Handbook of Micro/Nano Tribology, 2020
Fredric Ericson, Jan-Åke Schweitz
Adhesion is the single most important mechanical property of a film—substrate composite because without it the composite could not exist. It is of interest not only in the context of thin-film adhesion (Mittal, 1978; Valli, 1986), but equally so in all types of bonded or sealed structures (Johansson et al., 1988b,c). In MST, flaking is a frequently observed problem such as in silicon nitride films on silicon substrates. Similarly, the limited strength of bonded structures produced by, for example, field-assisted bonding (anodic bonding) or Si direct bonding (fusion bonding) has been a problem to many workers. Sometimes a deposited film will flake or spall off spontaneously as a result of strong internal stresses in the system. In other cases flaking is the result of external bending moments. In yet other cases neither internal nor external causes seem to be able to detach the film; it just sticks to the substrate for good. Sometimes a careful pretreatment of the surface combined with an equally careful optimization of the deposition parameters is sufficient to produce a well-adhered film.
Fluidic Interconnects for Microfluidics: Chip to Chip and World to Chip
Published in Sushanta K. Mitra, Suman Chakraborty, Fabrication, Implementation, and Applications, 2016
Another concept of importance in the literature, most notably with respect to WTC interconnects, is the concept of permanent versus reworkable interconnects. Permanent interconnects are usually those that are formed via a bond that cannot be easily removed, such as interconnects being integrated into the overall system flow or interconnects realized by direct material-to-material bonding. Such direct bonding may include high-temperature fusion bonding, anodic bonding (for glass and silicon), or adhesive bonding (glues such as epoxy or other curable material). Reworkable interconnects are those where the attachment is not permanent, relying, for example, on some spring-loaded mechanism or material compliance for direct substrate-to-substrate attachment, or screws in a jig for stacked systems to hold the two halves of the interconnect together. Reworkable interconnects often use a gasket, which is a compliant material used to aid in mating two hard surfaces such that they form a leak-tight interface. A popular type of gasket is a simple torus or an o-ring. This differs from a ferrule, which is a name for a type of metal or plastic object (usually a ring) that is used for fastening, joining, or reinforcement.
Progress in wafer bonding technology towards MEMS, high-power electronics, optoelectronics, and optofluidics
Published in International Journal of Optomechatronics, 2020
Jikai Xu, Yu Du, Yanhong Tian, Chenxi Wang
Direct bonding is to join homo/heterogeneous materials by the means of surface activation, such as ultraviolet, plasma, and fast atom beam. The surface energy after activation will be improved, which is beneficial for direct bonding. Besides, the bonding interface is sharp and nanometer-scale because the whole process is intermediate-free. The direct bonding method is not only suitable for Si-based materials (i.e., Si, SiO2, and glass), it can also be used for the wide-bandgap semiconductors (e.g., SiC and GaN). Combined with the ion implantation technique, the direct bonding method has great potential in the fabrication of high-quality SiC- or GaN-based heterogeneous structures toward optoelectronics. Moreover, batch fabrication for single-crystal thin-film transfer of the wide-bandgap generation of semiconductors can also be achieved. Cu/Cu and Cu/dielectric direct bonding are important technologies for high-density three-dimensional (3 D) integration. Due to the interconnection is bump-free, it is beneficial to obtain stacked structures with ultrasmall volumes. Low-temperature homo/heterogeneous direct bonding can be achieved with H-contained HCOOH vapor or fast argon atom beam treatment.[23–25] Lithium niobate (LiNbO3) is a promising candidate for future photonic quantum computation due to its excellent electro-optical properties. However, current modulators suffer from bulk and poor modulations. Integrating single-crystal LiNbO3 thin film onto other substrates is expected to address these problems. However, because of the chemical inertness, LiNbO3-on-insulator (LNOI) is difficult to fabricate. Utilizing the Smart-Cut process and developing a reliable LiNbO3 bonding method can realize this target.
Room temperature direct bonding of diamond and InGaP in atmospheric air
Published in Functional Diamond, 2022
Jianbo Liang, Yuji Nakamura, Yutaka Ohno, Yasuo Shimizu, Yasuyoshi Nagai, Hongxing Wang, Naoteru Shigekawa
On the basis of the experimental results, we found that the intermediate layer formed at the bonding interface was composed of C, In, Ga, P, and O atoms; the ununiform of the intermediate layer in the thickness was attributed to the morphology of the InGaP surface due to rough surface (Figure 1(c)). For the room temperature direct bonding, the surface roughness of bonding materials is a very important factor. The Ra value of bonding material surface smaller than 1 nm was necessary for achieving the direct bonding of diamond and semiconductor substrates [11,13]. Although the Ra value (2.93 nm) of the InGaP surface was larger than 1 nm, the direct bonding of diamond and InGaP was achieved. The main reason was due to the chemical reaction occurred between the oxide layer formed on InGaP and the C = O and C-O chemical bonds formed on the diamond after contacting. The oxide layer should originate from the In-OH, Ga-O, P-O, O-Ga, and O-H chemical bonds formed on InGaP, as shown in Figure 2. Since there is no alloy composed of C, Ga, In, and P atoms, it is difficult to find a long-distance mutual diffusion at the interface. Moreover, there is not a stable phase composed of the In-OH, Ga-O, P-O, O-Ga, O-H, C = O, and C-O chemical bonds. Therefore, each element at the interface should move after annealing. The increased amorphous layer thickness should be associated with the oxygen atoms moving. In fact, the oxygen intensity peak is moving to the InGaP side as shown in Figure 4e. On the other hand, the rich In atom layer formed at the diamond side of the bonding interface should also play an important role in the direct bonding of diamond and InGaP. It has been reported that the direct bonding of Si wafer using an indium tin oxide layer at low temperatures was achieved [19]. In addition, wafer bonding using a thin indium film at 140 °C has also been reported [20].
Recent progress on additive manufacturing of multi-material structures with laser powder bed fusion
Published in Virtual and Physical Prototyping, 2022
Di Wang, Linqing Liu, Guowei Deng, Cheng Deng, Yuchao Bai, Yongqiang Yang, Weihui Wu, Jie Chen, Yang Liu, Yonggang Wang, Xin Lin, Changjun Han
The methods to bond dissimilar materials at the interface of multi-material structures involve the direct bonding method (Bartolomeu et al. 2020; Chen, Yang et al. 2019; Tan et al. 2018), composition transition method (Demir and Previtali 2017; Wen et al. 2021; Zhang et al. 2020), and intermediate bonding layer method (Onuike and Bandyopadhyay 2018; Tey et al. 2020). The direct bonding method directly melts dissimilar materials, which enables the formation of a strong interface when the materials possess similar thermal properties. A compatible intermediate bonding layer between dissimilar materials is effective in eliminating the incompatibility of physical/chemical properties between dissimilar materials, which can create a strong and durable bonding interface. Moreover, the intermediate bonding layer method is often used to avoid the generation of detrimental phases between dissimilar materials. Ti/steel multi-material structures exhibit a favourable combination of corrosion resistance from titanium alloys and various properties (oxidation resistance, excellent hardness, good machinability, etc.) from relatively low-cost steels, which can potentially be applied in the nuclear power, chemical, and aerospace industries (Bobbio et al. 2017; Reichardt et al. 2016). However, detrimental Fe-Ti intermetallic compounds could form in the direct bond between steel and titanium. Tey et al. (2020) obtained a Ti6Al4 V/Hovadur® K220 copper/316L SS multi-material part using LPBF, in which K220 copper was the intermediate bonding layer (Figure 11(a)). Although the copper intermediate bonding layer could avoid the generation of Fe-Ti intermetallic compounds at the K220 copper/316L SS interface, they found that three detrimental phases existed at the interface of Ti6Al4 V/K220 copper (Figure 11(b)), i.e. the L21 ordered phase, amorphous phase, and Ti2Cu, deteriorating the mechanical strength of the multi-material part. Figure 11(c) shows the fracture paths at the interface of Ti6Al4 V/K220 copper. Interestingly, cracks initiated from the amorphous phase and then propagated within the β-Ti + Ti2Cu phase mixture. Finally, cracks can be diverted towards the K220 copper interlayer through a deflection around the α′-Ti phase. Therefore, the Ti6Al4 V/K220 copper samples achieved a high tensile strength by raising the interfacial volume fraction of the α′-Ti phase.