Monolithic complementary field-effect transistors having carbon-doped release layers
Embodiments of the disclosure advantageously provide semiconductor devices CFET in particular and methods of manufacturing such devices having a fully strained superlattice structure with channel layers that are substantially free of defects and release layers having a reduced selective removal rate. The CFET described herein comprise a vertically stacked superlattice structure on a substrate, the vertically stacked superlattice structure comprising: a first hGAA structure on the substrate; a sacrificial layer on a top surface of the first hGAA structure, the sacrificial layer comprising silicon germanium (SiGe) having a germanium content in a range of from greater than 0% to 50% on an atomic basis; and a second hGAA structure on a top surface of the sacrificial layer. Each of the first hGAA and the second hGAA comprise alternating layers of nanosheet channel layer that comprise silicon (Si) and nanosheet release layer that comprise doped silicon germanium (SiGe).
1. A method of forming a semiconductor device, the method comprising:
forming a vertically stacked superlattice structure on a substrate by
forming a first horizontal gate-all-around (hGAA) structure on a substrate;
forming a sacrificial layer on a top surface of the first hGAA structure, the sacrificial layer comprising silicon germanium (SiGe) having a germanium content in a range of from greater than 0% to 50% on an atomic basis; and
forming a second horizontal gate-all-around (hGAA) structure on a top surface of the sacrificial layer,
wherein each of the first hGAA structure and the second hGAA structure comprise alternating layers of nanosheet channel layer and nanosheet release layer, each nanosheet channel layer independently comprising silicon (Si) and each nanosheet release layer independently comprising silicon germanium (SiGe) doped with a dopant, and wherein each nanosheet release layer has an etch rate that is reduced compared to the sacrificial layer.
2. The method of claim 1 , wherein the sacrificial layer comprises silicon germanium (SiGe) having a germanium content in a range of from 20% to 50% on an atomic basis.
3. The method of claim 2 , wherein each nanosheet release layer comprises silicon germanium (SiGe) having a germanium content in a range of from 10% to 30% on an atomic basis.
4. The method of claim 3 , wherein the sacrificial layer comprises silicon germanium (SiGe) having a germanium content in a range of from greater than 30% to 50% on an atomic basis and wherein each nanosheet release layer comprises silicon germanium (SiGe) having a concentration in a range of from greater than 15% to 20% on an atomic basis doped with carbon having a carbon concentration in a range of from greater than 0% to less than or equal to 2% on an atomic basis.
5. The method of claim 1 , wherein the sacrificial layer has a thickness in a range of from 15 nm to 90 nm.
6. The method of claim 1 , wherein each of the first hGAA structure and the second hGAA structure have in a range of from 1 to 5 pairs of alternating layers of nanosheet channel layer and nanosheet release layer.
7. The method of claim 1 , wherein the dopant comprises one or more of carbon (C), and boron (B).
8. The method of claim 7 , wherein the silicon germanium (SiGe) of each nanosheet release layer is doped with carbon (C).
9. The method of claim 8 , wherein doping the silicon germanium (SiGe) of each nanosheet release layer with carbon (C) reduces strain in the vertically stacked superlattice structure and permits a higher growth temperature and an increased growth rate.
10. The method of claim 7 , wherein the dopant has a concentration in a range of from greater than 0% to less than or equal to 2% dopant on an atomic basis.
11. The method of claim 1 , wherein the etch rate is reduced by a factor of at least 2.
12. The method of claim 1 , wherein the vertically stacked superlattice structure is fully strained and each nanosheet channel layer is substantially free of defects.
13. The method of claim 1 , further comprising selectively removing the sacrificial layer.