Integrated field emission array for ion desorption
View Patent ↗An integrated field emission array for ion desorption includes an electrically conductive substrate; a dielectric layer lying over the electrically conductive substrate comprising a plurality of laterally separated cavities extending through the dielectric layer; a like plurality of conically-shaped emitter tips on posts, each emitter tip/post disposed concentrically within a laterally separated cavity and electrically contacting the substrate; and a gate electrode structure lying over the dielectric layer, including a like plurality of circular gate apertures, each gate aperture disposed concentrically above an emitter tip/post to provide a like plurality of annular gate electrodes and wherein the lower edge of each annular gate electrode proximate the like emitter tip/post is rounded. Also disclosed herein are methods for fabricating an integrated field emission array.
1. A method of semiconductor manufacturing, comprising:
depositing a top silicon oxide film on a silicon substrate;
depositing a polysilicon etch-stop film over the top silicon oxide film;
etching an annular isolation trench through the polysilicon etch-stop film and the top silicon oxide film;
depositing a silicon nitride layer that overlies the top silicon oxide film and fills the annular isolation trench;
etching an annular recess through the silicon nitride layer such that the etched annular recess is concentric with and surrounded by the silicon-nitride-filled annular trench in the top silicon oxide film;
deepening the annular recess by anisotropically etching the polysilicon etch-stop film through the annular recess etched in the silicon nitride layer;
lining the annular recess with a conformally deposited polysilicon sidewall film;
etching the top silicon oxide film through the polysilicon-lined annular recess using an isotropic etching process such that an annular cavity having a rounded cross section forms in the top silicon oxide film and partially undercuts the silicon nitride layer; and
filling the annular cavity in the top silicon oxide film with metal.
2. The method of claim 1 , wherein the metal filling the annular cavity comprises tungsten.
3. The method of claim 1 , further comprising, before depositing the top silicon oxide film, the following steps directed at forming a silicon post having a sharp tip positioned such that the metal-filled annular cavity is substantially centered about said tip:
etching an annular post-defining trench in the silicon substrate so as to define a silicon post surrounded by the post-defining trench;
filling the post-defining trench with a sacrificial fill of silicon oxide;
depositing a photoresist mask over the silicon post; and
isotropically etching the silicon post beneath the photoresist mask so as to define the sharp tip.