Fast atom beam-activated n-Si/n-GaAs wafer bonding with high interfacial transparency and electrical conductivity

Abstract

Optically transparent, electrically conductive n-Si/n-GaAs direct wafer bonds are achieved by athorough optimization of surface conditioning using fast atom beams. Bonding at room temperature under high-vacuum conditions is systematically investigated after in situ surface deoxidization using either argon or helium fast atom beams. Using argon, high bond energies of up to 900 mJ/m2 areobtained and further enhanced to achieve bulk strength through rapid annealing at 290 C, thereby enabling the production of thermally stable and mechanically robust hybrid substrates. Moreover, the interface conductivity is significantly improved by an additional thermal annealing at 400 C. Although it is anticipated to induce higher quality interfaces, helium treatment yields, however, limited and unstable bonding. This difference is attributed to an important surface nano-texturing that occurs during fast atom beam processing, a phenomenon that is peculiar to helium and absent in argon treatment

Transparent and electrically conductive GaSb/Si direct wafer bonding at low temperatures by argon-beam surface activation

“…In Fig. 4, it is shown, that the bond resistance decreases, when the samples are annealed for 1 min at 350 • C instead of 300 • C. It has been already observed for direct bonds between GaAs and Si, that the amorphous layer at the interface is partly recrystallized during annealing, resulting in lower resistances [4]. Surprisingly, all samples annealed at 400 • C show a higher bond resistance (compare Table 1).…”

“…In the case of silicon, it was shown by Essig et al and Howlader et al that the RMS roughness is not altered by the Ar atom bombardment using comparable atom energies and doses [4,20].…”

“…The monolithic integration of III-V semiconductors on silicon offers a wide range of innovative applications, like in the fields of power electronics [1], photonics [2] and photovoltaics [3,4]. III-V layers on silicon allow combining favorable material characteristics of compound semiconductors with the low-cost, the mechanical stability and the advantages in the processing of silicon.…”

“…III-V layers on silicon allow combining favorable material characteristics of compound semiconductors with the low-cost, the mechanical stability and the advantages in the processing of silicon. Hence, direct wafer bonding between GaAs/Si [4,5] and InP/Si [5,6] was investigated extensively in the past years. Likewise, GaSb offers a wide choice of promising and unique characteristics such as small effective masses, high electron and hole mobilities and a band gap suitable for long-wavelength optical devices [7,8].…”

III-V/Si wafer bonding using transparent, conductive oxide interlayers

“…Typical direct wafer bonding methods include either a high temperature * Adele.Tamboli@nrel.gov treatment [8], where thermal expansion mismatch can be problematic, or a plasma activation step [9], which can result in oxidation of the semiconductors and surface damage [10,11]. Recently, equipment has been developed to enable surface activation in situ using a fast atom beam treatment, which prevents oxidation [11][12][13], a method that has resulted in 30% efficiency triple junction Ga 0.5 In 0.5 P/GaAs//Si solar cells under concentrated sunlight [14]. However, this specialized tool requires a UHV chamber equipped with fast atom or ion beam sources.…”