Modification of Si(100)-Surfaces by SF6 Plasma Etching — Application to Wafer Direct Bonding

Abstract

The effect of plasma pretreatments (reactive ion etching in SF6 and SF6/O2) on Si/Si wafer direct bonding was investigated. Etching in SF6 caused a bonding behaviour generally known from hydrophobic (HF etched) samples, whereas adding O2 to the feed gas caused the Si(100) surfaces to become hydrophilic and spontaneous bonding was achieved. The structure of the bonded interfaces were analysed by high‐resolution electron microscopy, ellipsometry, multiple internal reflection spectroscopy, and secondary ion mass spectroscopy. All the plasma treatments result in an interface structure analogous to that known from bonded hydrophobic wafer pairs. The interface does not involve an additional layer such as an SiO2 or an amorphous Si layer but small one‐dimensional defects forming a disturbed layer about 1 to 2 nm thick.

<title>Heterogeneous substrates for high-temperature and optical applications</title>

“…The treatment in the SF 6 /O 2 plasma causes an analogous surface structure as for HF dipping (i.e. a complete removing of the oxide) but a bonding behaviour similar to hydrophilic bonded wafer pairs 23) . Analogous pin-diodes were also prepared on SOI wafers having different top layer thicknesses (Figure 3c).…”

Degradation of polymer films

“…185 Plasmas can have many different effects depending on the chemistry and energies involved, including removal of material (see Fig. 3), cross-linking and chemical reaction.…”

“…In particular C 4 F 8 and SF 6 plasmas are routinely used in microengineering to etch silicon as part of the Bosch process. 185 Ion bombardment of a silicon based surface with fluorine plasmas is mostly a physical process with few chemical reactions possible. Ion bombardment in these cases only provide the activation energy necessary for etching reactions on the substrate surface where weakly bonded molecules are formed and subsequently desorbed into the gas phase, essentially becoming a sputtering process.…”

Adhesive technology for photonics

“…More O 2 added to the feed gas results in higher surface roughness. 66 It is also well known that increasing surface roughness by plasma etching usually improves adhesion. However, the adhesion strength after plasma treatment has been shown to be lower than that of samples with no plasma treatment.…”