Method of making non-uniformly nitrided gate oxide
AssigneeHarris Corporation
InventorsAkira Ito, John T. Gasner
Life of this patent
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Abstract
A method of making a semiconductor device in which a polysilicon gate is separated from a semiconductor substrate by a re-oxidized nitrided oxide film and in which the concentration of re-oxidized nitride in the film underlying the gate is non-uniform. The concentration of nitrogen in the substrate and the re-oxidized nitrided oxide along their interface and underlying the gate is non-uniform. The non-uniform concentrations are provided by incomplete shielding of the oxide by the gate during the nitriding and re-oxidizing processes.
Claims19
A method of forming a gate oxide having a non-uniform concentration of re-oxidized nitrided oxide for a semiconductor device comprising the steps of:
- a) forming an oxide film on the upper surface of a semiconductor substrate;
- b) forming a polysilicon layer on the oxide film;
- c) selectively removing the polysilicon layer to define a polysilicon gate with the oxide film underlying the polysilicon gate defining a gate oxide;
- d) exposing the oxide film to a nitrogen containing ambient to thereby nitride the oxide film and to form a region of non-zero nitrogen concentration along an interface of the semiconductor substrate and the oxide film;
- and
- e) exposing the nitrided oxide film to a dry oxygen ambient to thereby form a re-oxidized nitrided oxide film in which a concentration of re-oxidized nitrided oxide is non-zero, and in which the re-oxidized nitrided oxide film and the region of non-zero nitrogen concentration underlie the entirety of the gate.
In a method of forming a re-oxidized nitrided oxide region in a semiconductor device having an oxide film formed on a semiconductor substrate and a polysilicon gate formed on the oxide film, the improvement comprising forming the polysilicon gate on the oxide film prior to nitriding and re-oxidizing the oxide film and nitriding and re-oxidizing the oxide film so that the re-oxidized nitrided oxide region extends completely under the gate and has a non-zero concentration of re-oxidized nitrided oxide.
A method, in a semiconductor device having an oxide film formed on a semiconductor substrate and a polysilicon gate formed on the oxide film, of
- (i) forming a gate oxide having a non-uniform concentration of re-oxidized nitrided oxide within said oxide film, and
- (ii) forming a nitrogen region along an interface of the oxide film and substrate having a non-uniform concentration of nitrogen under the gate oxide, the method comprising the steps of:
- a) forming an oxide film on an upper surface of a semiconductor substrate;
- b) forming a polysilicon layer on the oxide film;
- c) selectively removing the polysilicon layer to define a polysilicon gate having a width with the oxide film under the polysilicon gate defining a gate oxide;
- d) exposing the oxide film and polysilicon gate for between about 1 and 180 seconds to a nitrogen containing ambient having a temperature between about 900.degree. C. and 1200.degree. C., the polysilicon gate partially shielding the gate oxide from exposure to the nitrogen containing ambient and thereby non-uniformly nitriding the gate oxide over the width thereof and forming a nitrogen region having a non-uniform concentration of nitrogen under the gate oxide;
- and
- e) exposing the oxide film for between about 10 and 180 seconds to a dry oxygen ambient having a temperature between about 900.degree. C. and 1200.degree. C., thereby forming a gate oxide having a non-uniform and non-zero concentration of re-oxidized nitrided oxide over an entirety of the width thereof.
A method of providing a non-uniform concentration of nitrogen in a semiconductor substrate underlying a gate oxide comprising the step of incompletely shielding the gate oxide with a gate prior to nitriding the gate oxide and nitriding the gate oxide so that the non-uniform concentration of nitrogen is greater than zero and extends completely under the gate.
A method of providing a non-uniform boron diffusion barrier between a boron doped polysilicon gate and an underlying semiconductor substrate comprising the step of incompletely shielding a gate oxide between the polysilicon gate and the substrate prior to nitriding the gate oxide and nitriding the gate oxide so that the non-uniform concentration of nitrogen is greater than zero and extends completely under the gate.
Dependencies are inferred from the claim text.