Capacitor electrode having an interface layer of different chemical composition formed on a bulk layer

Abstract

An improved capacitor that is less susceptible to the depletion effect and methods for providing the same. The capacitor comprises a first and second electrode and an insulating layer interposed therebetween. The first electrode includes a bulk layer comprising n-doped polysilicon. The first electrode also includes an interface layer extending from a first surface of the bulk layer to the insulating layer. The interface layer is heavily doped with phosphorus so that the depletion region of the first electrode is confined substantially within the interface layer. The method of forming the interface layer comprises depositing a layer of hexamethldisilazane (HMDS) material over the first surface of the bulk layer so that HMDS molecules of the HMDS material chemically bond to the first surface of the bulk layer. The method further comprises annealing the layer of HMDS material in a phosphine ambient so as to replace CHmethyl groups with PHmolecules. The interface layer is then passivated in a nitrogen ambient having a reduced temperature so as to reduce the number of dangling silicon bonds of the lower electrode in a manner that results in reduced thermal damage to neighboring circuit elements.