Room-temperature wafer bonding of Si to LiNbO₃, LiTaO₃and Gd₃Ga₅O₁₂by Ar-beam surface activation

Abstract

A room-temperature wafer bonding method using surface activation by Ar-beam sputter etching were applied to the bonding between dissimilar materials. LiNbO 3 , LiTaO 3 and Gd 3 Ga 5 O 12 wafers were successfully bonded to Si wafers without any heat treatment. This method is free from the various problems caused by the large thermal expansion mismatch between these materials during heat treatment in the conventional wafer bonding processes. The bond prepared by the Ar-beam treatment is so strong that fracture from inside the bulk materials is observed after the tensile test. The results of the bonding of Si wafers to both 128 • Y-cut and Z-cut LiNbO 3 wafers indicate that the influence of the crystal orientation on the bonding strength is negligible in this method. This method provides a very low damage bonding process for various material combinations regardless of any thermal expansion mismatch or crystal lattice mismatch.

UV epoxy bonding for enhanced SAW transmission and microscale acoustofluidic integration

“…Principally, these difficulties relate to the bonding of piezoelectric materials which, when joined using conventional electrothermal routes, produce tremendous interfacial stresses 19,20 -an issue reflected in the fact that nearly all SAW micropumps that have been developed to date are employ open channels or planar, chemically treated, surfaces. [21][22][23] Alternative techniques such as surface activated bonding using an argon beam, 24 for example, have somewhat addressed this issue by allowing room temperature processing, but, such methods require sample manipulation within high-vacuum environments and a notably atypical vacuum chamber configuration (for example, the MWB-04 by Sojitsu Manufacturing/ Mitsubishi Heavy Industries, Tokyo, Japan), making this route both impractical and prohibitively expensive. As a consequence, researchers have turned to soft lithography, 25 a popular molding technique using a cast liquid elastomer, typically polydimethylsiloxane (PDMS), in order to form microchannels.…”

Direct bonding of two crystal substrates at room temperature by Ar-beam surface activation

“…The bonded area in the specimen was only the 9 Â 9 mm 2 square at the center, and it was surrounded by the 2 mm wide non-bonded area. This structure was helpful in bonding strength measurement [18]. Metal blocks were glued to each specimen; 32 pieces, except several pieces on the edge of the bonded wafer pair, were subjected to a tensile test.…”

“…6 shows the fracture surface of Si-sapphire bonding after a tensile test. Here, small chips cut from wafers were used [18]. The specimen was not subjected to any heat treatment.…”

Magneto-Optical Nonreciprocal Devices for Silicon Photonics

“…When integrating a magneto-optical garnet with other materials for optical waveguide applications, a tight, uniform contact between the materials is required for obtaining a sufficient interaction between the light waves and magneto-optical garnet. A surface activated direct bonding technique is a powerful tool to realize a tight contact between dissimilar crystals [24][25][26]. We developed a surface activated direct bonding technique for integrating a magneto-optical garnet on a silicon waveguide [14].…”