| AVS 65th International Symposium & Exhibition | |
| Applied Surface Science Division | Thursday Sessions |
| Session AS-ThP |
| Session: | Applied Surface Science Division Poster Session |
| Presenter: | Brian Baker, Arizona State University |
| Authors: | B. Baker, Arizona State University J. Kintz, Arizona State University A. Yano, Arizona State University N. Herbots, Arizona State University W.-L. Lee, Cactus Materials, Inc. S.R. Narayan, Arizona State University J.M. Day, Arizona State University R. Islam, Cactus Materials, Inc. Y. Watznabe, TDC Coporation M. Koury, Arizona State University M. Johnson, Arizona State University R.J. Culbertson, Arizona State University M. Magnus, Arizona State University |
| Correspondent: | Click to Email |
In this work, piezoelectric LiTaO3(100) and alpha-quartz SiO2(100) wafer bonding is investigated via NanoBonding™ near 300K [1,2]. NanoBonding™ generates molecular bonds between surfaces at the nanoscale over large interfacial domains, creating a 2D bonding interphase between the two materials. First, electron exchange is created between surfaces by engineering a key hydrophilic-hydrophobic surface pairs (via wet chemical processes, spin, vapor, or plasma etching). This method catalyzes electronic exchange and bonding by modifying native surfaces to a less stable state where electronic displacement is enhanced. Surface Energy Modification is measured via the surface total energy γT, and its three components γLW, γ+, γ-. These values are based on the Van Oss-Chaudury-Good (vOCG) theory, and using high resolution Three Liquid Contact Angle analysis. A key feature of Surface Energy Modification for NanoBonding™ is the creation of 2D precursor phases on surfaces. Next, for nanocontacting, the surface has to be planarized at the macro, micro, and nano scales. Last, NanoBonding™ activation can occur on contact and/or after thermal activation.
NanoBonding™ depends thus on the control of surface energy, planarity at three scales, and composition. γT can be computed from 3LCAA. The liquids used are 18 MO water, glycerin, and α-bromo-naphthalene (10 10 µL droplets). The average γT, across as received 4” LiTaO3 wafer is 43.3 ± 2 mJ/m2 (hydrophobic). However, the electron acceptor energy Y(-) can vary from 43 mJ/m2 to 23 mJ/m2 (~50% difference). Regions with low Y(-) (low electron transfer) do not bond while those high Y(-) do. This correlates directly with bonded interfacial regions visualized when LiTaO3 wafer is nano-contacted with 4” quartz wafers. In this way, 3LCAA can determine one cause of bonding failures.
Thermal activation (100 and 200°C) does not enhance bonding as significant thermal expansion causes mismatch fractures, interface delamination, or thermal decomposition due to the high mobility of Li ions.
In conclusion, thermally or plasma activated wafer bonding is clearly not optimal for wafer bonding LiTaO3. To Si-based materials, causing high fracture rates for LiTaO3 as well Li out diffusion. Instead, Nanobonding(TM) is more appropriate due to a reduced fracture or thermal decomposition chance.
Herbots N. et al. US Pat. No 9,018,077 (2015), US Pat. No 9,018,077 (2017)
Herbots N., Islam R., US Pat. Pending (2018), filed March 18, 2018