The SESiBon(1)) project under the EU Growth programme has focussed on the investigation and exploitation of various silicon bonding techniques. Both standard silicon to pyrex wafer bonding and the more advanced silicon-to-silicon thin film anodic bonding has been investigated. Here we present the results of the work done to enable bonding of structured wafer surfaces, allowing lateral feed-throughs into sealed cavities.Lateral feed throughs are formed by means of RIE in a high-doped poly-silicon film deposited on an oxidized 4" silicon wafer. Next a BPSG (Boron Phosphorus Silicate Glass) layer is deposited in a PECVD reaction chamber onto the structured surface. The BPSG is used as an intermediate planarization layer. Planarization is done by annealing the wafer in a N2-O2-H2O ambient for 4 - 8h @ 900 degreesC. After planarization the two wafers are bonded together, sealing the cavities.Our work with BPSG has proven that although it is not trivial, planarization of structured wafer surfaces to a flatness necessary for bonding is feasible. It is necessary to design the lateral feed-through structures in accordance with the BPSG floating properties allowing space for the glass to flow into the valleys of the surface.
|Title of host publication||Semiconductor wafer bonding VII : science, technology, and applications : proceedings of the International Symposium|
|Publisher||The Electrochemical Society|
|Publication status||Published - 2003|
Fléron, R., & Jensen, F. (2003). Sealing of cavities with lateral feed-throughs by anodic bonding. In Semiconductor wafer bonding VII : science, technology, and applications : proceedings of the International Symposium (pp. 337-345). The Electrochemical Society.