Chemical analysis of bonded and debonded silicon-glass interfaces

We report on the nature of the interface of anodically bonded glass wafers (Pyrex 7740, Hoya SD-2) and silicon wafers, after having reversed the voltage across the wafer couples. The reaction products and defects discovered at the interface of the wafers are studied with scanning electron microscopy, electron dispersive x-ray spectroscopy and with an electron microprobe. An accumulation, especially of sodium, is found to be closely related to the presence of defects appearing as brown/yellow-brown spots and cracks. Gradients in potassium and zinc concentrations are also observed in regions containing defects. Some of the processes that are believed to take place in the interface region are discussed.