Preventing threshold voltage variability in stacked nanosheets
AssigneeInternational Business Machines Corporation
InventorsMichael A. Guillorn, Nicolas J. Loubet
Life of this patent
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Abstract
Embodiments are directed to a method of forming a stacked nanosheet and resulting structures having equal thickness work function metal layers. A nanosheet stack is formed on a substrate. The nanosheet stack includes a first sacrificial layer formed on a first nanosheet. A hard mask is formed on the first sacrificial layer and the first sacrificial layer is removed to form a cavity between the hard mask and the first nanosheet. A work function layer is formed to fill the cavity between the hard mask and the first nanosheet.
Claims20
A method for forming a semiconductor device, the method comprising:
- forming a nanosheet stack on a substrate, the nanosheet stack comprising a first sacrificial layer on a first nanosheet;
- forming a hard mask directly on a surface of the first sacrificial layer;
- forming a first doping region against a first end of the nanosheet stack, and forming a second doping region against a second end of the nanosheet stack opposite the first end;
- completely removing the first sacrificial layer to form a cavity between the hard mask and the first nanosheet;
- and
- forming a work function layer to fill the cavity between the hard mask and the first nanosheet.
A method for forming a semiconductor device, the method comprising:
- forming a first sacrificial layer on a substrate;
- forming a first nano sheet on the first sacrificial layer;
- forming a second sacrificial layer on the first nanosheet;
- forming a hard mask directly on a surface of the second sacrificial layer;
- forming a first doping region against a first end of the first sacrificial layer and the first nanosheet, and forming a second doping region against a second end of the first sacrificial layer and the first nanosheet opposite the first end;
- completely removing the first and second sacrificial layers to form a first cavity between the first nanosheet and the substrate and a second cavity between the hard mask and the first nanosheet;
- and
- forming a first work function layer to fill the first cavity and a second work function layer to fill the second cavity;
- wherein a thickness of the first work function layer is substantially equal to a thickness of the second work function layer.
A semiconductor device comprising:
- a nanosheet stack formed over a substrate, the nanosheet stack comprising a topmost nanosheet vertically stacked between a top work function layer and a bottom work function layer;
- a gate formed over a channel region of the nanosheet stack;
- first and second spacers formed on opposing sidewalls of the gate;
- a conductive layer formed between the gate and the top work function layer;
- a first electrically conductive doping region against a first end of the nanosheet stack, and a second electrically conductive doping region against a second end of the nanosheet stack opposite the first end, the first and second doping regions extending from a first end that contacts the substrate to an opposing second end that extends above the top work function layer and contacts the first and second spacers, respectively,
- wherein a thickness of the top work function layer is substantially equal to a thickness of the bottom work function layer.
Dependencies are inferred from the claim text.