Methods for removal of selected nanowires in stacked gate all around architecture

1. A structure, comprising:

a substrate;

a first set of fins disposed on the substrate, the first set of fins comprising a first stack comprised of a first plurality of vertically stacked first Si nanowires that are spaced apart by a first distance;

a second set of fins disposed on the substrate comprised of a second plurality of vertically stacked second Si nanowires that are spaced apart by a second distance that is greater than the first distance, where in a given fin of the second set of fins there are fewer vertically stacked second Si nanowires than vertically stacked first Si nanowires in a given fin of the first set of fins, where the first set of fins and the second set of fins have approximately the same total thickness;

a first oxide layer and a metal layer disposed on each of the first Si nanowires; and

a second oxide layer and a metal layer disposed on each of the second Si nanowires, where the second oxide layer disposed on the second Si nanowires is thicker than the first oxide layer disposed on the first Si nanowires, and where the first oxide layer is comprised of a layer of high dielectric constant metal oxide and where the second oxide layer is comprised of a layer of silicon oxide having an overlying layer of high dielectric constant metal oxide.

2. The structure as in claim 1 , where the first set of fins and the second set of fins are formed by a process that comprises:

depositing a first plurality of layer pairs on the substrate, where each layer pair of the first plurality of layer pairs is comprised of a layer of Si having a first thickness and a layer of SiGe having a second thickness;

removing in a region of the substrate where the second set of fins will be formed the deposited first plurality of layer pairs;

depositing in the region a second plurality of layer pairs on the substrate, where at least one layer pair of the second plurality of layer pairs is comprised of layer of Si having the first thickness and at least one layer of SiGe having a third thickness that is greater than the first thickness;

removing the layers of SiGe from the first plurality of layer pairs leaving a first plurality of vertically stacked first Si nanowires that are spaced apart by the first distance that corresponds to the second thickness;

removing the layers of SiGe from the second plurality of layer pairs leaving a second plurality of vertically stacked second Si nanowires that are spaced apart by the second distance that corresponds to the third thickness; and

forming the first oxide layer and the metal layer on each of the first Si nanowires and the second oxide layer and the metal layer on each of the second Si nanowires.

3. The structure as in claim 1 , where the first set of fins and the second set of fins are formed by a process that comprises:

depositing a plurality of layer pairs on the substrate, where each layer pair of the plurality of layer pairs is comprised of a layer of Si having a first thickness and a layer of SiGe having a second thickness;

in a portion of the deposited layer pairs where the second set of fins will be formed, implanting Ge into at least one of the layers of Si so as to convert the implanted Si layer into a layer comprised of SiGe that is interposed between two adjacent layers of SiGe to form a thicker layer of SiGe having a third thickness;

removing the layers of SiGe in a portion of the deposited layer pairs where the first set of fins will be formed leaving the first plurality of vertically stacked first Si nanowires that are spaced apart by the first distance, where the first distance corresponds to the second thickness;

removing the layers of SiGe in the portion of the substrate where the second set of fins will be formed leaving the second plurality of vertically stacked second Si nanowires that are spaced apart by the second distance that corresponds to the third thickness; and

forming the first oxide layer and the metal layer on each of the first Si nanowires and the second oxide layer and the metal layer on each of the second Si nanowires.

4. The structure as in claim 3 , further comprising performing one of a solid-phase epitaxy or a solid-phase crystallization (SPE/SPC) operation at a predetermined temperature to heal implant-induced damage, where the predetermined temperature is less than about 700° C.

5. The structure as in claim 1 , where the first set of fins and the second set of fins are formed by a process that comprises:

depositing a plurality of layer pairs on the substrate, where each layer pair is comprised of a layer of Si having the first thickness and a layer of SiGe having the second thickness, and where depositing the plurality of layer pairs also deposits a first layer of Ge adjacent to a first surface of a layer of Si of at least one layer pair and a second layer of Ge adjacent to a second opposite surface of the layer of Si, where the layer of Si and the first and second layers of Ge are interposed between a first layer of SiGe and a second layer of SiGe, each layer of Ge having a third thickness that is less than the first and second thicknesses;

forming the first set of fins in a first region of the deposited plurality of layers and the second set of fins a second region in a second region of the deposited plurality of layers;

in the first set of fins, removing the layers of SiGe and the layers of Ge leaving the first plurality of vertically stacked first Si nanowires that are spaced apart by the first distance that is substantially equal to the second thickness plus the third thickness;

in the second set of fins, performing an anneal at a predetermined temperature to intermix the layers of Ge with the layer of Si that is interposed between the layers of Ge, and the layers of SiGe, to form a layer of SiGe having a fourth thickness; and

in the second set of fins, removing the layers of SiGe leaving the second plurality of vertically stacked second Si nanowires that are spaced apart by the second distance that is substantially equal to the third thickness plus the fourth thickness.

6. The structure as in claim 2 , where the first thickness is about 8 nm to about 10 nm, where the second thickness is about 8 nm to about 10 nm, and where the third thickness is about three times the first thickness.

7. The structure as in claim 5 , where the first thickness is about 8 nm to about 10 nm, where the second thickness is about 8 nm to about 10 nm, where the third thickness is about 2 nm to about 3 nm, and where the fourth thickness is about three times the first thickness.

8. The structure as in claim 1 , where the metal layer disposed on each of the first Si nanowires extends vertically between adjacent Si nanowires in the first set of fins, and where the metal layer disposed on each of the second Si nanowires extends both vertically and horizontally between adjacent Si nanowires in the second set of fins.

9. A structure, comprising:

a substrate;

a first set of fins disposed on the substrate, the first set of fins comprising a first stack comprised of a first plurality of vertically stacked first Si nanowires that are spaced apart by a first distance;

a second set of fins disposed on the substrate comprised of a second plurality of vertically stacked second Si nanowires that are spaced apart by a second distance that is greater than the first distance, where in a given fin of the second set of fins there are fewer vertically stacked second Si nanowires than vertically stacked first Si nanowires in a given fin of the first set of fins, where the first set of fins and the second set of fins have approximately the same total thickness;

a first oxide layer and a metal layer disposed on each of the first Si nanowires, where the metal layer disposed on each of the first Si nanowires comprises at least one of TiN, TiC, TiAlC, TaN, TaC, TaAlC, TaSiN, HfN, W, Al, and Ru; and

a second oxide layer and a metal layer disposed on each of the second Si nanowires, where the second oxide layer disposed on the second Si nanowires is thicker than the first oxide layer disposed on the first Si nanowires, and where the first oxide layer is comprised of a layer of high dielectric constant metal oxide and where the second oxide layer is comprised of a layer of silicon oxide having an overlying layer of high dielectric constant metal oxide.

10. The structure as in claim 9 , where the metal layer disposed on each of the second Si nanowires comprises at least one of TiN, TiC, TiAlC, TaN, TaC, TaAlC, TaSiN, HfN, W, Al, and Ru.