Method for fabricating a field-effect transistor having a floating gate
AssigneeInfineon Technologies AG
InventorsFranz Hofmann, Georg Tempel, Robert Strenz, Robert Wiesner
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Abstract
In the course of a method for fabricating a field-effect transistor having a floating gate, a structure is formed which has uncovered sidewalls of a layer made of the material for forming the floating gate and which is exposed to an oxidizing atmosphere in order to coat the sidewalls. At the same time, other regions of the structure have an insulating oxide layer. At a point in time prior to the action of an oxidizing atmosphere, nitrogen is implanted into the material of the floating gate in a quantity that appreciably reduces the oxidation at the sidewalls thereof.
Claims19
A method for fabricating a field-effect transistor having a floating gate, which comprises the steps of:
- providing a semiconductor substrate having a surface;
- forming a layer construction on a part of the surface of the semiconductor substrate, the layer construction containing, as a bottommost layer, a tunnel dielectric for the floating gate, above that an intermediate layer made of a material of the floating gate and, as a topmost layer, a coupling dielectric having a nitride layer;
- implanting, after an application of the nitride layer of the coupling dielectric, nitrogen into the material of the floating gate in a quantity for appreciably reducing oxidation at sidewalls of layer construction, the nitrogen being implanted through the nitride layer into the material of the floating gate;
- patterning the layer construction to form the sidewalls defining part of a contour of the floating gate and resulting in a patterned layer construction;
- subsequently, coating a remaining part of the substrate surface and the sidewalls of the layer construction with an oxide layer through an action of an oxidizing atmosphere;
- subsequently, applying a further material for forming a control gate;
- patterning a geometry of an overall layer construction formed of the patterned layer construction and the further material for forming the control gate to a desired contour resulting in a patterned overall layer construction;
- and
- performing a post-oxidation of all surfaces including the sidewalls of the patterned layer construction resulting in a post oxide.
A method for fabricating a field-effect transistor having a floating gate, which comprises the steps of:
- providing a semiconductor substrate having a surface;
- forming a layer construction on a part of the surface of the semiconductor substrate, the layer construction containing, as a bottommost layer, a tunnel dielectric for the floating gate, above that an intermediate layer made of a material of the floating gate and, as a topmost layer, a coupling dielectric having a nitride layer;
- patterning the layer construction for forming sidewalls defining part of a contour of the floating gate and resulting in a patterned layer construction, the patterning being performed with a selective etching to a final depth reaching at least as far as a lower end of the material of the floating gate;
- implanting nitrogen into the material of the floating gate in a quantity for appreciably reducing oxidation at the sidewalls, the nitrogen being implanted into a sidewall of the material of the floating gate uncovered by the selective etching;
- coating a remaining part of the substrate surface and the sidewalls of the layer construction with an oxide layer through an action of an oxidizing atmosphere;
- subsequently, applying a further material for forming a control gate;
- patterning a geometry of an overall layer construction formed of the patterned layer construction and the further material for forming the control gate to a desired contour resulting in a patterned overall layer construction;
- and
- performing a post-oxidation of all surfaces including the sidewalls of the layer construction resulting in a post oxide.
Dependencies are inferred from the claim text.