Forming source and drain regions for sheet transistors
A semiconductor device is provided. The semiconductor device includes an n-doped field effect transistor (nFET) section, a p-doped field effect transistor (pFET) section and an insulator pillar. The nFET section includes nFET nanosheets and nFET source or drain (S/D) regions partially surrounding the nFET nanosheets. The pFET section includes pFET nanosheets and pFET S/D regions partially surrounding the pFET nanosheets. The insulator pillar is interposed between the nFET S/D regions and the pFET S/D regions to form a fork-sheet structure with the nFET nanosheets and the pFET nanosheets.
1. A method of fabricating a semiconductor device, the method comprising:
forming an insulator pillar between n-doped and p-doped field effect transistor (nFET and pFET) sections;
growing sacrificial undoped source or drain (S/D) regions in the nFET and pFET sections;
masking the sacrificial undoped S/D regions in one of the nFET and pFET sections and a portion of the insulator pillar exposed above the sacrificial undoped source or drain (S/D) regions in the nFET and pFET sections, the masking comprising extending a mask from a first side of the insulator pillar to beyond an opposite side and etching the mask back to parallel with the opposite side such that the portion of the insulator pillar comprises:
an entirety of an uppermost surface thereof; and
a portion of a sidewall thereof at the opposite side, which is exposed above the sacrificial undoped S/D regions in the corresponding one of the nFET and pFET sections;
etching the sacrificial undoped S/D regions in the other of the nFET and pFET sections; and
sequentially growing doped S/D regions in the other of the nFET and pFET sections and the one of the nFET and pFET sections.
2. The method according to claim 1 , wherein:
the forming of the insulator pillar comprises forming the insulator pillar to have a width of about 10 nm or less, or
the forming of the insulator pillar comprises forming the insulator pillar to have a width of about 8 nm.
3. The method according to claim 1 , wherein the forming of the insulator pillar comprises forming the insulator pillar to comprise:
an uppermost surface taller than respective uppermost surfaces of the doped S/D regions with respect to a substrate; and
sidewalls disposed in contact with respective short edges of nFET and pFET nanosheets surrounded by doped S/D regions in the nFET and pFET sections, respectively.
4. The method according to claim 1 , wherein:
the masking of the sacrificial undoped S/D regions in the one of the nFET and pFET sections comprises forming a liner, and
the liner prevents doped S/D regions breach during the growing of the doped S/D regions in the other of the nFET and pFET sections.
5. The method according to claim 1 , wherein the masking of the sacrificial undoped S/D regions in the one of the nFET and pFET sections comprises forming a divot fill during epitaxy patterning to avoid overlay error.
6. The method according to claim 1 , wherein the insulator pillar and the nFET and pFET sections are formed on a substrate pillar and shallow trench isolation (STI) elements surrounding portions of the substrate pillar.
7. The method according to claim 1 , further comprising:
forming interlayer dielectric (ILD) around respective portions of the doped S/D regions in the nFET and pFET sections and the insulator pillar; and
forming first and second contacts extending through the ILD to make contact with the doped S/D regions in the nFET and pFET sections.
8. The method according to claim 1 , further comprising forming one or more gate structures traversing the nFET section, the insulator pillar and the pFET section.
9. The method according to claim 1 , further comprising:
masking the sacrificial undoped S/D regions in the other of the nFET and pFET sections and a portion of the insulator pillar exposed above the sacrificial undoped source or drain (S/D) regions in the nFET and pFET sections, the masking comprising extending a mask from the opposite side of the insulator pillar to beyond the first side and etching the mask back to parallel with the first side such that the portion of the insulator pillar comprises:
an entirety of an uppermost surface thereof; and
a portion of a sidewall thereof at the first side, which is exposed above the sacrificial undoped S/D regions in the corresponding one of the nFET and pFET sections; and
etching the sacrificial undoped S/D regions in the one of the nFET and pFET sections.
10. A method of fabricating a semiconductor device, the method comprising:
forming an insulator pillar between n-doped and p-doped field effect transistor (nFET and pFET) sections;
growing sacrificial undoped source or drain (S/D) regions in the nFET and pFET sections;
masking the sacrificial undoped S/D regions in one of the nFET and pFET sections, the masking comprising:
lining a sidewall of the insulator pillar which is exposed above the sacrificial undoped S/D regions at a first side of the insulator pillar;
extending a mask from the first side of the insulator pillar to beyond an opposite side;
etching the mask back from the opposite side to beyond the liner at the first side; and
filling a space between a remainder of the mask and the liner at the first side;
etching the sacrificial undoped S/D regions in the other of the nFET and pFET sections; and
sequentially growing doped S/D regions in the other of the nFET and pFET sections and the one of the nFET and pFET sections.
11. The method according to claim 10 , further comprising:
masking the sacrificial undoped S/D regions in the other of the nFET and pFET sections, the masking comprising:
lining a sidewall of the insulator pillar which is exposed above the sacrificial undoped S/D regions at the opposite side of the insulator pillar;
extending a mask from the opposite side of the insulator pillar to beyond the first side;
etching the mask back from the first side to beyond the liner at the opposite side; and
filling a space between a remainder of the mask and the liner at the opposite side;
etching the sacrificial undoped S/D regions in the one of the nFET and pFET sections.
12. A method of fabricating a semiconductor device, the method comprising:
forming an insulator pillar between n-doped and p-doped field effect transistor (nFET and pFET) sections, the nFET section comprising nanosheets and the pFET section comprising nanosheets;
growing sacrificial undoped source or drain (S/D) regions in the nFET and pFET sections;
masking the sacrificial undoped S/D regions in one of the nFET and pFET sections;
etching the sacrificial undoped S/D regions in the other of the nFET and pFET sections;
repeating the masking and the etching in the other of the nFET and pFET sections and in the one of the nFET and pFET sections, respectively; and
sequentially growing doped S/D regions in the other of the nFET and pFET sections to surround the corresponding nanosheets therein and the one of the nFET and pFET sections to surround the corresponding nanosheets therein,
wherein the masking comprises masking the sacrificial undoped S/D regions in the one or the other of the nFET and pFET sections, and
the masking comprises lining a sidewall of the insulator pillar which is exposed above the sacrificial undoped S/D regions, extending a mask across the insulator pillar, etching the mask back across the insulator pillar and filling a space between a remainder of the mask and the liner.
13. The method according to claim 12 , wherein the nanosheets comprise remainders of silicon germanium layers in the nFET and pFET sections.