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US 4,397,075 AGranted
FET Memory cell structure and process
AssigneeInternational Business Machines Corporation
InventorsJoseph J. Fatula, Jr., Paul L. Garbarino
Life of this patent
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Abstract
A dense, vertical MOS FET memory cell has a high charge storage capacitance per unit area of substrate surface. The charge storage capacitor structure is formed within a well etched in the silicon semiconductor substrate by a combination of reactive ion etching and a self-limiting wet etch.
Claims11
A method for producing a dense MOS FET memory device having a vertical capacitor comprising
- providing a monocrystalline silicon substrate having a gate including a gate dielectric layer on said substrate, a gate electrode layer on said dielectric layer and source and drain regions in said substrate on opposite sides of said gate;
- reactive ion etching a substantially U-shaped opening into said substrate in said drain region adjacent to said gate;
- growing a silicon dioxide layer on the surface of said U-shaped opening;
- reactive ion etching said U-shaped opening deeper into said substrate to form a deeper U-shaped opening;
- etching said deeper opening with a directional etchant to form a well having an enlarged buried opening;
- removing by etching said silicon dioxide from said well;
- diffusing an impurity into the surfaces of said well and;
- forming electrical contacts to the source and to said gate electrode layer.
5 more elements
A method for producing a vertical capacitor comprising:
- providing a monocrystalline silicon substrate of a first conductivity type and having a region of a second conductivity type in said substrate;
- reactive ion etching a substantially U-shaped opening into said substrate into and through said region of second conductivity type;
- growing a silicon dioxide layer on the surface of said U-shaped opening;
- reactive ion etching said U-shaped opening deeper into said substrate to form a deeper U-shaped opening;
- etching said deeper opening with a directional etchant to form a well having an enlarged buried opening;
- removing by etching said silicon dioxide from said well;
- diffusing an impurity into the surfaces of said well;
- and
- forming electrical contact to the said region of second conductivity type.
6 more elements
Dependencies are inferred from the claim text.