Time-Dependent Surface Properties and Wafer Bonding of O[sub 2]-Plasma-Treated Silicon (100) Surfaces

Abstract

Low‐temperature wafer direct bonding is considered a key tool for the fabrication of bulk micromechanic devices. The possibility of enhancing the bonding energy by applying an O2 plasma treatment before bonding has been the focus of recent studies. Here, the effect of storage following the plasma treatment, as well as the duration of the latter on the attainable activation of the surface, the bonding strength, and bubble generation, have been investigated. Immediately after the plasma treatment bond energies up to 1.6J/m2 are achieved. However, 50 h after the treatment bonded wafer pairs show bonding energies up to only 1.3J/m2 . The duration of the plasma treatment strongly affects the number, size, and distribution of interface bubbles. © 2000 The Electrochemical Society. All rights reserved.

Advances in fabrication of X-ray waveguides

“…For this reason, plasma cleaned wafers are often found to be highly covered with voids (b), affecting the local bonding quality. Substituting the plasma cleaning by an RCA bath decreases the number of (small) bubbles significantly, while hardly reducing the bonding strength between the wafers [31]. Contamination is identified as the dominant mechanism of generating large bubbles at the RCA cleaned wafers, since micronsized particles induce voids with a diameter up to several centimeters.…”

Self-assembled monolayers of perfluoroalkylsilane on plasma-hydroxylated silicon substrates

“…Contact angle is the included angle between the gas-liquid and the solid-liquid interface, which can be visually shown in Fig. 4, where sg is the surface tension of solid-gas interface, and lg was the surface tension of liquid-gas interface [44]. According to the models of Fowkes [45] and Owens and Wendt [40], both the solid superficial energy and the liquid surface tension can be separated into two terms: (i) the polar contributions due to Coulomb interactions and (ii) the disperse contributions due to van der Waals forces.…”

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“…Chemical processing methods which have been investigated include: chemical cleaning [1], oxygen plasma exposure [2,3], and argon sputtering/in-situ oxidation [4]. It is desirable for commercial applications to develop a cleaning/surface activation method that does not require elevated temperatures or exotic bonding conditions.…”

“…(1) other materials besides silicon can be bonded, (2) wet chemistry is eliminated, and (3) the energetic ions of plasma are not required [2,3].…”