Silicon-silicon anodic-bonding with intermediate glass layers using spin-on glasses

This paper presents for the first time the preparation of glass layers, suitable for the anodic bonding of two silicon substrates using a spin-on glass. In this process a liquid sol solution is used within a spin coating process. The solution is a mixture based on silica sol, organic silicon containing compounds, like TEOS (Tetraethylorthosilicate), and a sodium salt all dissolved in ethanol. After a careful thermal treatment, silica films containing up to 5% wt. Na₂O (sodium oxide) can be obtained with a thickness in the range from 600 nm to 1000 nm in one deposition step. The spin-on glass films are very smooth. Anodic bonding of two silicon substrates is possible with all films either prepared at temperatures of 420°C, 540°C or even higher