Single work function metal and multiple threshold voltage scheme
Embodiments of the invention include forming a first transistor having first nanosheets, first dipole gate dielectric material being formed around the first nanosheets. An aspect includes forming a second transistor comprising second nanosheets, second dipole gate dielectric material being formed around the second nanosheets, the first and second transistors being in a vertical stack, a first spacing between the first nanosheets being different from a second spacing between the second nanosheets. An aspect includes forming a workfunction metal stack having a first workfunction metal and a second workfunction metal, the first and second workfunction metals being formed between the first nanosheets, the first workfunction metal being formed to pinch off in the second spacing between the second nanosheets such that the second workfunction metal is absent in the second spacing between the second nanosheets.
1 . A method comprising:
forming a first transistor comprising first nanosheets, first dipole gate dielectric material being formed around the first nanosheets;
forming a second transistor comprising second nanosheets, second dipole gate dielectric material being formed around the second nanosheets, the first and second transistors being in a vertical stack, a first spacing between the first nanosheets being different from a second spacing between the second nanosheets; and
forming a workfunction metal stack comprising a first workfunction metal and a second workfunction metal, the first and second workfunction metals being formed between the first nanosheets, the first workfunction metal being formed to pinch off in the second spacing between the second nanosheets such that the second workfunction metal is absent in the second spacing between the second nanosheets.
2 . The method of claim 1 , wherein the first and second transistors in the vertical stack are complementary devices in which one is an n-type transistor and another one is a p-type transistor.
3 . The method of claim 1 , wherein one of the first and second dipole gate dielectric materials has a negative polarity and another one has a positive polarity.
4 . The method of claim 1 , wherein both the first and second dipole gate dielectric materials have a negative polarity.
5 . The method of claim 1 , wherein both the first and second dipole gate dielectric materials have a positive polarity.
6 . The method of claim 1 , wherein:
the first transistor is an n-type transistor having the first and second workfunction metals formed between the first nanosheets without requiring etch back of the second workfunction metal on the second transistor; and
the first workfunction metal is an n-type workfunction metal and the second workfunction metal is a p-type workfunction metal.
7 . The method of claim 1 , wherein:
the second transistor is a p-type transistor having the first workfunction metal formed between the second nanosheets without requiring etch back of the second workfunction metal on the second transistor; and
the first workfunction metal is an n-type workfunction metal and the second workfunction metal is a p-type workfunction metal.
8 . A semiconductor structure comprising:
a first transistor comprising first nanosheets, first dipole gate dielectric material being formed around the first nanosheets;
a second transistor comprising second nanosheets, second dipole gate dielectric material being formed around the second nanosheets, the first and second transistors being in a vertical stack, a first spacing between the first nanosheets being different from a second spacing between the second nanosheets; and
a workfunction metal stack comprising a first workfunction metal and a second workfunction metal, the first and second workfunction metals being formed between the first nanosheets, the first workfunction metal being formed to pinch off in the second spacing between the second nanosheets such that the second workfunction metal is absent in the second spacing between the second nanosheets.
9 . The semiconductor structure of claim 8 , wherein the first and second transistors in the vertical stack are complementary devices in which one is an n-type transistor and another one is a p-type transistor.
10 . The semiconductor structure of claim 8 , wherein one of the first and second dipole gate dielectric materials has a negative polarity and another one has a positive polarity.
11 . The semiconductor structure of claim 8 , wherein both the first and second dipole gate dielectric materials have a negative polarity.
12 . The semiconductor structure of claim 8 , wherein both the first and second dipole gate dielectric materials have a positive polarity.
13 . The semiconductor structure of claim 8 , wherein:
the first transistor is an n-type transistor having the first and second workfunction metals formed between the first nanosheets without requiring etch back of the second workfunction metal on the second transistor; and
the first workfunction metal is an n-type workfunction metal and the second workfunction metal is a p-type workfunction metal.
14 . The semiconductor structure of claim 8 , wherein:
the second transistor is a p-type transistor having the first workfunction metal formed between the second nanosheets without requiring etch back of the second workfunction metal on the second transistor; and
the first workfunction metal is an n-type workfunction metal and the second workfunction metal is a p-type workfunction metal.
15 . A method comprising:
forming a vertical stack having a first transistor below a second transistor, the first transistor comprising first nanosheets, the second transistor comprising second nanosheets, first dipole gate dielectric material being formed around the first nanosheets, second dipole gate dielectric material being formed around the second nanosheets, a first spacing between the first nanosheets being different from a second spacing between the second nanosheets;
forming another vertical stack having another first transistor below another second transistor, the another first transistor comprising another first nanosheets, the another second transistor comprising another second nanosheets, the first dipole gate dielectric material being formed around the another second nanosheets, the second dipole gate dielectric material being formed around the another first nanosheets, the first spacing between the another first nanosheets being different from the second spacing between the another second nanosheets; and
forming a workfunction metal stack comprising a first workfunction metal and a second workfunction metal, the first and second workfunction metals being formed between the first nanosheets and the another first nanosheets, the first workfunction metal being formed to pinch off in the second spacing between the second nanosheets and the another second nanosheets such that the second workfunction metal is absent in the second spacing between the second nanosheets and the another second nanosheets,
wherein the vertical stack has a different threshold voltage than the another vertical stack.
16 . The method of claim 15 , wherein:
the first and second transistors in the vertical stack are complementary devices in which one is an n-type transistor and another one is a p-type transistor; and
the another first and another second transistors in the another vertical stack are complementary devices in which one is another n-type transistor and another one is another p-type transistor.
17 . The method of claim 15 , wherein one of the first and second dipole gate dielectric materials has a negative polarity and another one has a positive polarity.
18 . The method of claim 15 , wherein both the first and second dipole gate dielectric materials have a negative polarity.
19 . The method of claim 15 , wherein both the first and second dipole gate dielectric materials have a positive polarity.
20 . The method of claim 15 , wherein:
the first transistor and the another first transistor are n-type transistors having the first and second workfunction metals formed between the first nanosheets and the another first nanosheets without requiring etch back of the second workfunction metal on the second transistor and the another second transistor; and
the first workfunction metal is an n-type workfunction metal and the second workfunction metal is a p-type workfunction metal.