Heterojunctions fabricated by surface activated bonding–dependence of their nanostructural and electrical characteristics on thermal process

Abstract

Recent achievements in research of heterojunctions fabricated using surface activated bonding (SAB), one of the practically useful direct wafer bonding technologies, are discussed. The response of bonding interfaces to post-bonding annealing is focused. These junctions reveal high thermal tolerance (1000 ○C in case of junctions made of widegap materials) despite difference in coefficients of thermal expansion between bonded materials. Defect layers with a several-nm thickness formed by the surface activation process at the as-bonded interfaces get faint and their electrical and mechanical properties are improved by annealing. These results show that as bonded interfaces are in a metastable state, and novel functional devices are likely to be realized by applying wafer processing steps to SAB-based junctions. Characteristics of III-V//Si multijunction solar cells, GaN-on-diamond high electron mobility transistors, and metal-foil based low-loss interconnects that are fabricated by processing SAB-based junctions are described, and the future prospects are presented.

Semiconductor Wafer Bonding for Solar Cell Applications: A Review

“…Wafer bonding has been employed to fabricate a variety of electronic and photonic devices, including field-effect transistors, [44][45][46] light-emitting diodes, [47][48][49][50][51] semiconductor lasers, [52][53][54][55][56][57][58][59] optical modulators, [60][61][62] photodetectors, [63][64][65] solar cells, and advanced concepts in optoelectronics. [66][67][68][69][70][71][72][73][74] Textbooks [75][76][77][78] and review articles [79][80][81][82][83][84][85][86][87][88] on wafer-bonding technologies and applications are available. Semiconductor wafer bonding is a crucial process used in various industries to integrate different materials and create complex structures.…”

Characterization of Ga-face/Ga-face and N-face/N-face interfaces with antiparallel polarizations fabricated by surface-activated bonding of freestanding GaN wafers

“…Low-temperature direct wafer bonding, bonding without heating wafers, is assumed to be preferable since a difference in coefficients of thermal expansion 11) between nitrides and other semiconductors could deteriorate the quality of bonding interfaces fabricated using conventional high temperature wafer bonding. Using surface activated bonding (SAB) technologies, 12,13) in which wafers are able to be bonded to each other without heating after activating their surfaces using fast atom beams (FAB) of Ar, Si/GaN, 14) GaAs/GaN, 15,16) and diamond/GaN 17) junctions were previously fabricated.…”

Fabrication and Electrical Characterization of GaAs/GaN Junctions

“…Low temperature wafer bonding technologies such as surface-activated bonding (SAB) (6) have been successfully applied for fabricating heterojunctions composed of semiconductors with different crystal structures and/or lattice constants (2). The electrical conduction across the SAB-based interfaces have been demonstrated (7). Using SAB, we previously bonded a GaAs epi wafer to a GaN layer epitaxially grown on a Si (111) substrate to investigate characteristics of fabricated GaAs/GaN diodes (8).…”