INVESTIGATION OF BURIED ETCH STOP LAYER IN SILICON MADE BY NITROGEN IMPLANTATION

A novel way to fabricate a buried etch stop layer in silicon is presented in this article. The etch stop layer is formed by nitrogen implantation and the investigations show that a dose of 1 . 10(17) N-14+-ions/cm2 at 140 keV is enough to effectively stop the silicon etch reaction in an ethylenediamine-pyrocatechol-water solution. The nitrogen concentration where the etch reaction stops was estimated with secondary ion mass spectroscopy measurement to be about 2.5 . 10(21) ions/cm3, which is far below the necessary concentration for nitride formation. As an application example, a 400 nm thin silicon membrane has been fabricated utilizing an etch stop layer formed by nitrogen implantation. By utilizing the anodic bonding and etchback technique, a silicon-on-insulator material with an extremely good surface flatness has also been formed. Finally, the nitrogen implanted silicon etch rate has been investigated with respect to different anneal temperatures. This result shows that the etch stop mechanism formed by the nitrogen implantation disappears when the anneal temperature exceeds 1000-degrees-C.