Integrated field emission array for ion desorption

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.