sodium ions. The deposition of such a layer requires a low-pressure chemical vapor deposition step. A disadvantage of sodium silicate bonding, however, is that it is very difficult to eliminate air bubbles. This is in part because the technique does not require a vacuum and also does not use field assistance as in anodic bonding. This lack of field assistance can sometimes be beneficial, because field assistance can provide such high attraction between wafers as to bend a thinner wafer and collapse onto nanofluidic cavity or MEMS elements.

Coatings