Gate spacer and inner spacer formation for nanosheet transistors having relatively small space between gates
Embodiments of the invention are directed to a nano sheet field effect transistor (FET) device that includes a gate spacer and an inner spacer. The gate spacer includes an upper segment and a lower segment. The inner spacer has a first selectivity to etch compositions used in predetermined fabrication operations for forming the inner spacer. The lower segment has the first selectivity to etch compositions used in predetermined fabrication operations for forming the inner spacer. The upper segment has a second selectivity to etch compositions used in predetermined fabrication operations for forming the inner spacer. The first etch selectivity is greater than the second etch selectivity.
1. A nanosheet field effect transistor (FET) device comprising:
a gate spacer; and
an inner spacer;
wherein the gate spacer comprises an upper segment and a lower segment;
wherein the inner spacer has a first selectivity to etch compositions used in predetermined fabrication operations for forming the lower segment and the inner spacer;
wherein the lower segment has the first selectivity to the etch compositions used in the predetermined fabrication operations for forming the lower segment and the inner spacer;
wherein the upper segment has a second selectivity to etch compositions used in the predetermined fabrication operations for forming the lower segment and the inner spacer; and
wherein the first etch selectivity is greater than the second etch selectivity such that the upper segment functions as a first mask in the predetermined fabrication operations for forming the lower segment.
2. The device of claim 1 , wherein the gate spacer is formed on a sidewall of a gate region of the nanosheet FET.
3. The device of claim 2 , wherein the upper segment is positioned above the lower segment.
4. The device of claim 3 , wherein:
the inner spacer is formed between channel nanosheets of the nanosheet FET;
the channel nanosheets have a third selectivity to etch compositions used in predetermined fabrication operations for forming the lower segment and the inner spacer; and
the first etch selectivity is greater than third etch selectivity such that the channel nanosheets function as a second mask in the predetermined fabrication operations for forming the inner spacers.
5. The device of claim 4 , wherein the inner spacer comprises a first material.
6. The device of claim 5 , wherein the lower segment comprises the first material.
7. The device of claim 6 , wherein the first material comprises the first etch selectivity.
8. The device of claim 7 , wherein the upper segment comprises a second material.
9. The device of claim 8 , wherein the second material comprises the second etch selectivity.
10. The device of claim 9 , wherein:
the first material comprises a first type of low-k material; and
the second material comprises a second type of low-k material.
11. A nanosheet field effect transistor (FET) device comprising:
gate spacers; and
inner spacers;
wherein each of the gate spacers comprises an upper segment and a lower segment;
wherein the inner spacers have a first selectivity to etch compositions used in predetermined fabrication operations for forming the lower segment and the inner spacers;
wherein the lower segments have the first selectivity to the etch compositions used in the predetermined fabrication operations for forming the lower segment and the inner spacers;
wherein the upper segments have a second selectivity to the etch compositions used in the predetermined fabrication operations for forming the lower segment and the inner spacers; and
wherein the first etch selectivity is greater than the second etch selectivity such that the upper segment functions as a first mask in the predetermined fabrication operations for forming the lower segment.
12. The device of claim 11 , wherein the gate spacers are formed on sidewalls of a gate region of the nanosheet FET.
13. The device of claim 12 , wherein each of the upper segments is positioned above one of the lower segments.
14. The device of claim 13 , wherein:
the inner spacers are formed between channel nanosheets of the nanosheet FET;
the channel nanosheets have a third selectivity to etch compositions used in predetermined fabrication operations for forming the lower segment and the inner spacers; and
the first etch selectivity is greater than third etch selectivity such that the channel nanosheets function as a second mask in the predetermined fabrication operations for forming the inner spacers.
15. The device of claim 14 , wherein the inner spacers comprises a first material.
16. The device of claim 15 , wherein the lower segments comprise the first material.
17. The device of claim 16 , wherein the first material comprises the first etch selectivity.
18. The device of claim 17 , wherein the upper segments comprise a second material.
19. The device of claim 18 , wherein the second material comprises the second etch selectivity.
20. The device of claim 19 , wherein:
the first material comprises a first type of low-k material; and
the second material comprises a second type of low-k material.