In situ investigation of ion drift processes in glass during anodic bonding

By means of in situ high-energy ion-beam analysis, which allows a quantitative multielement depth profiling, the formation of an anodic alkali-depleted polarization layer and of an oxygen-enriched interface layer has been investigated. Drift rates and depletion-layer thicknesses are determined as a function of the process temperature, bias and drift time. The drift behaviour of cations including potassium, calcium, aluminium and hydrogen has been examined. Finally, the drift of oxygen ions towards the compound interface is observed. The absence of non-bridging oxygen in TEMPAX, which has been proved by NMR investigations, gives rise to the conclusion that the drift behaviour of oxygen ions depends mainly on the composition of the 'leached' glass surface layer. The results confirm anodic oxidation as the main mechanism responsible for the actual interface chemistry. (C) 1998 Elsevier Science S.A. All rights reserved.