Silicon Wafer Direct Bonding without Hydrophilic Native Oxides

Abstract

Silicon wafer direct bonding was accomplished between two surfaces which had no hydrophilic native oxide layers. Prior to bonding, two wafers were dipped in conc-HF solution ( ∼49% aq.) to remove the native oxide layers and then immersed in deionized water. The level of bonding was evaluated by X-ray topography, high resolution transmission electron microscopy (HRTEM) and tensile strength measurement. It was found that the bonded wafer pairs were void-free and had good bonding strength. HRTEM observation showed that the crystal lattice was continuous and had only small distortions and precipitates. Spreading resistance (SR) measurement across the interface showed that the electric resistance did not increase at the bonding interface. It is suggested that the OH groups which substitute the F atoms terminated on the small portion of the surface play an important role in this conc-HF-treated bonding.

Nature of bonding forces between two hydrogen-passivated silicon wafers

“…29͒ between two isolated H overlayers is much smaller than the wafer-wafer van der Waals interaction and cannot account for the bonding energy. Although we cannot exclude that other effects may contribute to the bonding energy, such as OH groups or F atoms adsorbed on the surfaces, 8,9 our theoretical results show that such a hypothesis is not necessary to explain the measured bonding energy.…”

“…[4][5][6][7] To strengthen this bond, the wafers are subsequently annealed at high temperature, whereby hydrogen desorbs from the interlayer. 1,5 There have been several proposals for the origin of the initial room-temperature bond between the two H-passivated surfaces, including intrinsic bonding due to van der Waals forces between H atoms 4,5 and bonding caused by adsorbed OH groups 8 or F atoms. 9 In this paper, we investigate the nature of the bonding forces using first-principles techniques.…”

Insights into Interfacial Mechanism of CeO2/Silicon and Atomic-Scale Removal Process during Chemo-Mechanical Grinding of Silicon

“…The relative motion between the grinding wheel and the wafer surface causes the abrasives to exert a tangential force on the surface, and the down feed of the wheel causes the abrasives to exert pressure on the wafer surface. As the wheel is fed downward, the exposed abrasives in the wheel are the first to come into contact with the wafer surface, which has an oxide layer due to exposure to air. − Therefore, the chemical reaction occurs first between the exposed CeO 2 abrasives and the oxide layer on the wafer surface, and then material removal occurs with the relative motion between the grinding wheel and the wafer surface.…”

Partial SOI Structure by Wafer Direct Bonding through Amorphous Layer

“…Then the polycrystalline silicon layer is planarized, and the two bonding wafers are cleaned in RCA solution. After that, the two bonding wafers are immersed in conc-HF solution and then rinsed in de-ionized water before bonding, so that the bonding is made without native oxide at the bonding interface (5). In this paper this surface treatment is called HFtreatment hereafter.…”