ION DRIFT PROCESSES IN PYREX-TYPE ALKALI-BOROSILICATE GLASS DURING ANODIC BONDING

Electric field induced ion drift processes in alkali-borosilicate glas ses play a key role in the silicon-glass or metal-glass compound forma tion in anodic bonding processes. By means of ex situ and in situ ion- beam analysis, which allows a quantitative depth profiling of differen t elements, the formation of anodic, alkali depleted glass layers and of oxygen enriched interface layers was investigated. Drift rates and depletion layer thicknesses were determined in dependence of the proce ss temperature, bias, and drift time. The drift behavior of cations, i ncluding sodium, potassium, calcium, aluminum, and hydrogen, was exami ned. In addition, the drift of oxygen ions toward the compound interfa ce was investigated. The absence of nonbridging oxygen in the investig ated glass, verified by nuclear magnetic resonance investigations, giv es rise to the conclusion that the drift behavior of oxygen ions depen ds mainly on the composition of the ''leached'' glass surface layer. T he results confirm the anodic oxidation as the main mechanism responsi ble for the interface chemistry. The oxygen enrichment (oxidation) of the metal or silicon anode can be described by a reciprocal logarithmi c equation.