Method of forming spacers for a gate of a transistor
First Claim
1. A method for forming spacers of a gate of a field effect transistor, with the gate comprising flanks and a top and being located above a layer made of a semiconductor material, the method comprising:
- forming a dielectric layer covering the gate;
modifying the dielectric layer, after the forming, by putting the dielectric layer into a presence of a plasma comprising ions with a hydrogen base and/or ions with a helium base, and choosing conditions of the plasma, including an energy of the ions and an ion implantation dose, such that the modifying comprises implanting the ions by bombarding the dielectric layer with the ions in the plasma, the bombarding being anisotropic in a direction parallel to the flanks of the gate, which modifies at least portions of the dielectric layer that are located on the top of the gate and on sides of the gate and that are perpendicular to the flanks of the gate, and which retains unmodified portions of the dielectric layer covering the flanks of the gate or portions unmodified over an entire thickness thereof;
removing humidity from the modified dielectric layer at a temperature greater than an ambient temperature; and
removing the modified dielectric layer, after the step of removing the humidity, comprising;
selective etching of the modified dielectric layer relative to the layer made of the semiconductor material and relative to the unmodified portions of the dielectric layer, the selective etching comprising a dry etching at the ambient temperature when at atmospheric pressure, performed by putting the modified dielectric layer into a presence of a gaseous mixture comprising at least one first component having a hydrofluoric acid base, with the at least one first component transforming the modified dielectric layer into non-volatile residue, andonly after the dry etching, wet cleaning the non-volatile residue at the ambient temperature when at the atmospheric pressure, or, only after the dry etching, thermal annealing to sublimate the non-volatile residue.
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Abstract
A method is provided for forming spacers of a gate of a field effect transistor, the gate including flanks and a top and being located above a layer of a semiconductor material, the method including a step of forming a dielectric layer covering the gate; after the step of forming, at least one step of modifying the dielectric layer by putting the dielectric layer into presence of a plasma creating a bombarding of light ions; and at least one step of removing the modified dielectric layer including a dry etching performed by putting the modified dielectric layer into presence of a gaseous mixture including at least one first component with a hydrofluoric acid base that transforms the modified dielectric layer into non-volatile residue, and removing the non-volatile residue via a wet clean performed after the dry etching or a thermal annealing of sublimation performed after or during the dry etching.
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Citations
29 Claims
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1. A method for forming spacers of a gate of a field effect transistor, with the gate comprising flanks and a top and being located above a layer made of a semiconductor material, the method comprising:
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forming a dielectric layer covering the gate; modifying the dielectric layer, after the forming, by putting the dielectric layer into a presence of a plasma comprising ions with a hydrogen base and/or ions with a helium base, and choosing conditions of the plasma, including an energy of the ions and an ion implantation dose, such that the modifying comprises implanting the ions by bombarding the dielectric layer with the ions in the plasma, the bombarding being anisotropic in a direction parallel to the flanks of the gate, which modifies at least portions of the dielectric layer that are located on the top of the gate and on sides of the gate and that are perpendicular to the flanks of the gate, and which retains unmodified portions of the dielectric layer covering the flanks of the gate or portions unmodified over an entire thickness thereof; removing humidity from the modified dielectric layer at a temperature greater than an ambient temperature; and removing the modified dielectric layer, after the step of removing the humidity, comprising; selective etching of the modified dielectric layer relative to the layer made of the semiconductor material and relative to the unmodified portions of the dielectric layer, the selective etching comprising a dry etching at the ambient temperature when at atmospheric pressure, performed by putting the modified dielectric layer into a presence of a gaseous mixture comprising at least one first component having a hydrofluoric acid base, with the at least one first component transforming the modified dielectric layer into non-volatile residue, and only after the dry etching, wet cleaning the non-volatile residue at the ambient temperature when at the atmospheric pressure, or, only after the dry etching, thermal annealing to sublimate the non-volatile residue. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A method for forming spacers of a gate of a field effect transistor, with the gate comprising flanks and a top and being located above a layer made of a semiconductor material, the method comprising:
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forming a dielectric layer covering the gate; modifying the dielectric layer, after the forming, by putting the dielectric layer into a presence of a plasma comprising ions with a hydrogen base and/or ions with a helium base, and choosing conditions of the plasma, including an energy of the ions and an ion implantation dose, such that the modifying comprises implanting the ions by bombarding the dielectric layer with the ions in the plasma, the bombarding being anisotropic in a direction parallel to the flanks of the gate, which modifies at least portions of the dielectric layer that are located on the top of the gate and on sides of the gate and that are perpendicular to the flanks of the gate, and which retains unmodified portions of the dielectric layer covering the flanks of the gate or portions unmodified over an entire thickness thereof; pre-annealing the modified dielectric layer at a temperature greater than an ambient temperature to remove humidity from the modified dielectric layer; and removing the modified dielectric layer, after the pre-annealing, comprising; selective etching of the modified dielectric layer relative to the layer made of the semiconductor material and relative to the unmodified portions of the dielectric layer, the selective etching comprising a dry etching at the ambient temperature when at atmospheric pressure, performed by putting the modified dielectric layer into a presence of a gaseous mixture comprising at least one first component having a hydrofluoric acid base, with the at least one first component transforming the modified dielectric layer into non-volatile residue, and only after the dry etching, wet cleaning the non-volatile residue at the ambient temperature when at the atmospheric pressure, or, only after the dry etching, thermal annealing to sublimate the non-volatile residue.
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Specification