Enabling residue free gap fill between nanosheets
A semiconductor structure and a method for fabricating the same. The semiconductor structure includes at least a first channel region and a second channel region. The first channel region and the second channel region each include metal gate structures surrounding a different nanosheet channel layer. The metal gate structures of the first and second channel regions are respectively separated from each other by an unfilled gap. The method includes forming a gap fill layer between and in contact with gate structures surrounding nanosheet channel layers in multiple channel regions. Then, after the gap fill layer has been formed for each nanosheet stack, a masking layer is formed over the gate structures and the gap fill layer in at least a first channel region. The gate structures and the gap fill layer in at least a second channel region remain exposed.
1. A method for forming a semiconductor structure, the method comprising at least:
depositing a gap fill material over a plurality of channel regions such that the gap fill material surrounds and directly contacts gate structures surrounding nanosheet channel layers in each of the plurality of channel regions and further filling gaps between the gate structures;
etching away portions of the gap fill material situated between each of the plurality of channel regions and in contact with sidewalls of each of the gate structures in the plurality of channel regions, the etching forming a respective gap fill material layer between and in contact with the gate structures in each of the plurality of channel regions; and
after the portions of the gap fill material have been etched away, forming a masking layer over at least the gate structures and the gap fill material layer in at least a first channel region of the plurality of channel regions, wherein the gate structures and the gap fill material layer in at least a second channel region of the plurality of channel regions remain exposed.
2. The method of claim 1 , wherein forming the masking layer comprises:
depositing a masking material over at least the plurality of channel regions such that the masking material is in contact with the gate structures and the gap fill material layers; and
patterning the masking material to expose the gate structures and the gap fill material layer within the at least second channel region.
3. The method of claim 2 , wherein the masking material is deposited using a spin-on propylene glycol monomethyl ether acetate (PGMEA) process.
4. The method of claim 1 , further comprising:
while the at least first channel region is masked,
removing the gap fill material layer formed between and in contact with the gate structures in the at least second channel region.
5. The method of claim 4 , wherein removing the gap fill material layer comprises:
performing a wet strip of the gap fill layer.
6. The method of claim 5 , wherein the wet strip is a 4-Methyl-2 pentanol type strip.
7. The method of claim 5 , further comprising:
after the gap fill material layer has been removed, forming one or more metal layers on the gate structures within the at least second channel region.
8. The method of claim 5 , further comprising:
after the gap fill material layer has been removed, removing one or more metal layers of the gate structures within the at least second channel region.
9. The method of claim 8 , further comprising:
after the one or more metal layers have been removed, forming one or more new metal layers in place of the one or more metal layers that have been removed.
10. The method of claim 8 , further comprising:
after the one or more metal layers have been removed, removing the masking layer to expose the gate structures and gap fill material layer within the at least first channel region; and
removing the gap fill material layer formed within the at least first channel region.
11. The method of claim 10 , further comprising:
after the gap fill material layer formed within the at least first channel region has been removed, forming one or more metal layers on the gate structures within the at least first channel region and one or more new metal layers in place of the one or more metal layers that have been removed from the gate structures within the at least second channel region.
12. The method of claim 1 , wherein the gap fill material layer is an organic planarization layer comprising a low molecular weight high gap fill molecule that is not crosslinked.
13. The method of claim 1 , wherein the gap fill material layer is an organic planarization layer that is soluble in high polar casting solvents.
14. The method of claim 1 , wherein forming the masking layer comprises:
depositing a masking material that is resistant to solvents used for subsequently removing the gap fill material layer.