Low-temperature direct bonding of silicon nitride to glass

Abstract

Direct bonding may provide a cheap and reliable alternative to the use of adhesives. While direct bonding of two silicon surfaces is well documented, not much is known about direct bonding between silicon nitride and glass. This is unfortunate since silicon nitride is extensively used as an anti-reflection coating in the PV industry, often in contact with a shielding layer made of glass. A series of bonding experiments between glass and SiN was performed. The highest bonding quality, manifested by the highest bonding energy and lowest void area, was obtained with pairs that had been activated by nitrogen plasma followed by post-contact thermal annealing at 400 C. HRTEM imaging, HRTEM-EDS and EELS measurements performed on the thin films prepared from bonded samples by Focused Ion Beam (FIB) revealed a clear defect-free interface between the silicon nitride and the glass, 4 nm in thickness. ATR FT-IR measurements performed on activated surfaces prior to contact indicated the formation of silanol groups on the activated glass surface and a thin oxide layer on the silicon nitride. An increase in the bearing ratio of the glass following activation was noticed by AFM. A mechanism for bonding silicon nitride and glass is suggested, based on generation of silanol groups on the glass surface and on oxidation of the silicon nitride surface. The results point out the importance of exposure to air, following activation and prior to bringing the two surfaces into contact.

A Quick and Reproducible Silanization Method by Using Plasma Activation for Hydrophobicity‐Based Kinesin Single Molecule Fluorescence–Microscopy Assays

“…While the O 2 plasma activation resulted on average in lower contact angles compared to the HCl activation, some batches approached 90°indicating that in principle, plasma activation can achieve a sufficiently high hydroxy density on the surface. [47] In agreement with activation in a N 2 plasma reported to be better, [47] we measured a significantly higher contact angle of 82:5 � 2:2°(N ¼ 432) with less variability when using the N 2 plasma (see Table 4 for significance values). Yet, both O 2 and N 2 plasmas do not contain any hydrogen species for direct surface hydroxylation.…”

“…As a control, we plotted the results of the HCl and O 2 plasma activations of Figure 2A (note the zoom‐in of the y ‐axis). While the O 2 plasma activation resulted on average in lower contact angles compared to the HCl activation, some batches approached 90° indicating that in principle, plasma activation can achieve a sufficiently high hydroxy density on the surface [47] . In agreement with activation in a N 2 plasma reported to be better, [47] we measured a significantly higher contact angle of $${82.5 \pm 2.2}$$ ° ($${N = 432}$$ ) with less variability when using the N 2 plasma (see Table 4 for significance values).…”

“…Yet, both O 2 and N 2 plasmas do not contain any hydrogen species for direct surface hydroxylation. Instead, it is assumed that the exposure of the freshly plasma‐activated, reactive surfaces to ambient air results in surface‐silanol formation [47] . Thus, we tested whether an air plasma with its natural water content would be more effective.…”

Dielectric Surface Charge Engineering for Electrostatic Doping of Graphene

“…54 Thus, domains are formed on the Si 3 N 4 surface to form SiO 2 networks, which have a higher affinity to form silanol groups on the surface after plasma activation. 55,56 The SiO 2 domains saturated with silanol groups have a lower positive surface charge than the Si 3 N 4 surface, as shown by surface charge measurements after plasma activation, because SiO 2 forms also under normal ambient condition silanol dangling bonds. 57 Thus, the total positive charge at the Si 3 N 4 surface is lowered in comparison to the untreated one.…”

The Wafer-Level Integration of Single-Crystal LiNbO3 on Silicon via Polyimide Material

“…PI reaches a certain degree of curing after pre-baking (Figure 7b). Combining the above discussion and analysis of the bonding surface and the bonding interface, as well as the previously published reports [32][33][34][35], we can get the effect of O2 plasma on the surface of the PI film: (1) removing surface contaminants; (2) increasing the number of -OH (hydroxyl) groups pre unit area on the surface; (3) changing the surface structure and improving the diffusion capacity of water and gas on the surface. The experimental results show that the PI film becomes smoother and exhibits more significant hydrophilicity after O2 plasma treatment (Figure 7c).…”