Abstract
Charges in SiO2 are measured before and after anodic bonding by capacitance-voltage (C-V) sweeps on MOS-capacitors. A Pyrex piece covering 1/3 of the silicon MOS-wafer is bonded to the wafer, and the capacitors not covered by Pyrex are measured. The flat-band voltages of all capacitors shift towards more negative values after bonding, indicating increased positive oxide charge. The maximum observed shift corresponds to an increase in oxide fixed charge from 1.5e11cm-2 before bonding to 1.0e12cm-2 after bonding. The shift is largest for devices situated close to the Pyrex. Mobile charge is measured by BTS-cycles. The mobile charge concentration is also increased after bonding, from ~5e11cm-2 to ~1e12cm-2. It is not known whether the charges are injected from the Si substrate, from the Pyrex glass, or from electric discharge processes taking place during bonding. Further experiments will be done in order to establish the origin of the charges.
