Local gate height tuning by CMP and dummy gate design
The present disclosure describes fabricating devices with tunable gate height and effective capacitance. A method includes forming a first metal gate stack in a dummy region of a semiconductor substrate and a second metal gate stack in an active device region of the semiconductor substrate, and performing a chemical mechanical polishing (CMP) process using a slurry including charged abrasive nanoparticles. The first and second metal gate stacks are different in composition. The charged abrasive nanoparticles include a first concentration in the active device region different from a second concentration in the dummy region.
1. A method, comprising:
forming a first metal gate stack in a dummy region of a semiconductor substrate and a second metal gate stack in an active device region of the semiconductor substrate, the first and second metal gate stacks being different in composition; and
performing a chemical mechanical polishing (CMP) process using a slurry including charged abrasive nanoparticles, wherein the charged abrasive nanoparticles include a first concentration in the active device region different from a second concentration in the dummy region.
2. The method of claim 1 , wherein during the performing of the CMP process, a CMP polish rate to the first metal gate stack in the dummy region is different from a CMP polish rate to the second metal gate stack in the active device region, and
wherein after the performing of the CMP process, a height of the first metal gate stack is different from a height of the second metal gate stack.
3. The method of claim 1 , further comprising:
forming a first cut metal gate (CMG) in the dummy region and a second CMG in the active device region, wherein the first and second CMGs are different in composition; and
thereafter, performing another CMP process using the slurry including the charged abrasive nanoparticles.
4. The method of claim 1 , wherein the CMP process is a first CMP process and the slurry is a first slurry, wherein the method further comprises:
forming a first cut metal gate (CMG) in the dummy region and a second CMG in the active device region; and
thereafter, performing a second CMP process using a second slurry different from the first slurry.
5. The method of claim 1 , further comprising tuning a pH value of the slurry to provide the charged abrasive nanoparticles.
6. The method of claim 1 , wherein the first metal gate stack in the dummy region includes tungsten (W) at a first volume percentage, the second metal gate stack in the active region includes W at a second volume percentage greater than the first volume percentage,
wherein the charged abrasive nanoparticles include a positively charged abrasive nanoparticles, and
wherein after the performing of the CMP process, the first metal gate stack has a first height greater than a second height of the second metal gate stack.
7. The method of claim 1 , wherein the first metal gate stack in the dummy region includes tungsten (W) at a first volume percentage, the second metal gate stack in the active region includes W at a second volume percentage greater than the first volume percentage,
wherein the charged abrasive nanoparticles include a negatively charged abrasive nanoparticles, and
wherein after the performing of the CMP process, the first metal gate stack has a first height less than a second height of the second metal gate stack.
8. The method of claim 1 , wherein the first metal gate stack includes a filling metal and a first work function metal layer,
wherein the second metal gate stack includes the filling metal and a second work function metal layer,
wherein the filling metal includes tungsten (W), and
wherein the first and the second work function metal layers include titanium nitride (TiN) or tantalum nitride (TaN), titanium aluminum nitride (TiAlN), tungsten nitride (WN), titanium aluminum (TiAl), or combinations thereof.
9. The method of claim 8 , wherein the first work function metal layer is different from the second work function metal layer in composition.
10. The method of claim 1 , wherein the abrasive nanoparticles include zirconium oxide, zirconium nitride or a combination thereof.
11. A method, comprising:
providing a semiconductor substrate;
forming a first metal gate stack in a dummy region of the semiconductor substrate and a first second metal gate stack in an active device region of the semiconductor substrate;
performing a first chemical mechanical polishing (CMP) process to the first and second metal gate stacks using a first slurry, wherein the first slurry includes charged abrasive nanoparticles;
forming first cut metal gates (CMGs) having a first pattern density in the dummy region;
forming second CMGs having a second pattern density in the active device region; and
performing a second CMP process using a second slurry, wherein after the performing of the second CMP process, the first metal gate stack has a first height different from a second height of the second metal gate stack.
12. The method of claim 11 , wherein
the first CMGs in the dummy region includes SiN;
the second pattern density is less than the first pattern density;
the second slurry has a first polish rate to SiN less than a second polish rate to SiO 2 ; and
the first height is greater than the second height.
13. The method of claim 11 , wherein
the first CMGs in the dummy region includes silicon nitride (SiN);
the second pattern density is less than the first pattern density;
the second slurry has a first polish rate to SiN greater than a second polish rate to silicon oxide (SiO 2 ); and
the first height is less than the second height.
14. The method of claim 11 , wherein
the first CMGs in the dummy region includes SiO 2 ;
the second pattern density is less than the first pattern density;
the second slurry has a first polish rate to SiN greater than a second polish rate to SiO 2 ; and
the first height is greater than the second height.
15. The method of claim 11 , wherein
the first CMGs in the dummy region includes SiO 2 ;
the second pattern density is less than the first pattern density;
the second slurry has a first polish rate to SiN less than a second polish rate to SiO 2 ; and
the first height is less than the second height.
16. The method of claim 11 , wherein after the performing of the first CMP process, the first metal gate stack has a third height different from a fourth height of the second metal gate stack.
17. A method, comprising:
providing a semiconductor substrate having a dummy region and an active device region;
forming first metal gate stacks in the dummy region and second metal gate stacks in the active device region, wherein the first metal gate stacks include a filling metal having a first concentration in the first metal gate stacks, and wherein the second metal gate stacks include the filling metal having a second concentration in the second metal gate stacks, the first concentration being different from the second concentration; and
performing a chemical mechanical polishing (CMP) process using a slurry including positively charged abrasive nanoparticles,
wherein the positively charged abrasive nanoparticles are attracted by the filling metal, and
wherein after the performing of the CMP process, the first metal gate stacks have a first height different from a second height of the second metal gate stacks.
18. The method of claim 17 , further comprising:
forming a first cut metal gate (CMG) in the dummy region and a second CMG in the active device region; and
thereafter, performing another CMP process using the slurry.
19. The method of claim 17 , wherein the filling metal includes tungsten,
wherein the first and the second metal gate stacks each further include a work function metal layer including titanium nitride (TiN) or tantalum nitride (TaN), titanium aluminum nitride (TiAlN), tungsten nitride (WN), titanium aluminum (TiAl), or combinations thereof.
20. The method of claim 17 , wherein the first metal gate stacks have a first pattern density, and
wherein the second metal gate stacks have a second pattern density different from the first pattern density.