A novel method to avoid sticking of surface micromachined structures

Abstract

We have fabricated surface micromachined cantilevers and bridges of 500 nm polysilicon on 900 nat thermal oxide as the sacrificial layer. It is well known that the released structures tend to stick to the substrate during the drying period after the oxide etching in HF and the rinse process. In general it is necessary to solidify the liquid between the polysilicon and the substrate. Thus we have substituted the HF in successive exchange steps by the monomer divinylbenzene. The monomer was polymerized under ultraviolet light at room temperature. Finally the polymer was released in an oxygen plasma. To prevent the fabricated structures from sticking to the substrate after an accidental touch during operation we have built bumps under the polysilicon-structures to keep them in distance from the substrate.