Chemical role of oxygen plasma in wafer bonding using borosilicate glasses

Plasma-treated oxide layers are commonly used in wafer bonding applications . Borosilicate glass (BSG) layers deposited by low-pressure chemical vapor deposition treated with an O-2 plasma in reactive ion etching mode for 5 mi n at 0.6 W/cm(2) and rinsed with DI H2O readily bond to GaAs and Si. The ch emical role of this prebonding treatment was investigated using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The pe ak intensities for both the Si-O and B-O absorbance bands decreased in inte nsity as a result of the plasma treatment is consistent with the uniform sp uttering of 9.8 nm +/-0.8 nm of BSG. Polarization dependent ATR-FTIR reveal ed that the H2O/OH absorbance bands decreased in peak intensity with the OH groups being preferentially oriented perpendicular to the sample surface a fter the plasma treatment. The subsequent DI H2O rinse restores the water t o the surface while removing B2O3 from the BSG layer. This prebonding treat ment, therefore, results in a hydrophilic bond, but alters the composition of the BSG film at the bonded interface. (C) 2001 American Institute of Phy sics.